SMITHSONIAN MISCELLANEOUS COLLECTIONSVOLUME 65, NUMBER 14
THE SENSE ORGANS ON THE MOUTH-PARTS OF THE HONEY BEE
BYN. E. McINDOO, Ph. D.Bureau of Entomology, Washington, D. C.
(Publication 2381)
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONJANUARY 12, 1916
Z$t £ovt> QBaitimoxe (preeeBALTIMORE, Md!, U. S. A.
THE SENSE ORGANS ON THE MOUTH-PARTS OF THEHONEY BEEBy N. E. McIndoo, Ph. D.BUREAU OF ENTOMOLOGY, WASHINGTON, D. C.CONTENTS PAGEIntroduction and methods iExperiments to determine whether bees have likes and dislikes in regardto foods 31. Preliminary experiments in feeding bees foods containing varioussubstances 42. Experiments in feeding bees foods containing repellents 83. Experiments in feeding bees sweet foods 104. Experiments in feeding bees foods containing bitter substances. ... 145. Experiments in feeding bees foods containing sour substances 156. Experiments in feeding bees foods containing sodium salts 177. Experiments in feeding bees foods containing potassium salts 198. Summary of preceding experiments 20Morphology of the sense organs on the mouth-parts of the honey bee 211. Structure of the innervated hairs 22(a) Spinelike hairs 23(b) Peglike hairs 272. Structure of the olfactory pores 283. Disposition of the innervated hairs 32(a) Spinelike hairs 32(b) Peglike hairs 364. Disposition of the olfactory pores 365. The tactile sense of the honey bee 396. How bees eat liquid foods 417. Summary of sense organs 45Discussion of literature 46General discussion 51Literature cited 52Abbreviations 54INTRODUCTION AND METHODSLittle experimental work has ever been performed to determinewhether insects have a true gustatory sense, although the sense organson the mouth-parts of various insects have been studied considerably.At least three different kinds of sense organs on the mouth-parts haveSmithsonian Miscellaneous Collections, Vol. 65, No. 14
2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65been called organs of taste, but no one has ever attempted to prove ex-perimentally the function of these organs. Judging from the factthat insects prefer some foods to others and that certain insects oftenrefuse poisoned foods, it is generally believed that insects can taste,regardless of whether or not they have gustatory organs.At this place it is desirable to define the human senses of smelland taste, so that we may use the definitions as a basis for interpretingthe responses to the same or similar stimuli in the honey bee. Thesense of smell is called forth by substances in a gaseous or vaporouscondition, although gases dissolved in the liquids of the mouth maygive rise to actual tastes. The sense of taste is brought about by sub-stances either in solution when introduced into the mouth, or dis-solved by the liquids in the mouth. Parker and Stabler ( 1913) , afterexperimenting upon themselves, and Professor Parker upon othervertebrates, say
:
We therefore definitely abandon the idea that taste and smell differ on thebasis of the physical condition of the stimulus, a state of solution for taste,a gaseous or vaporous condition for smell, and maintain that both senses arestimulated by solutions, though in smell, at least for air-inhabiting vertebrates,the solvent is of a very special kind In air-inhabiting vertebrates theolfactory solvent is a slimy fluid of organic origin and not easily imitated.From the preceding definitions it is evident that the senses of smelland taste in vertebrates cannot be sharply separated, and the presentpaper will show that these two senses in the honey bee cannot beseparated at all. In the honey bee it will be shown that the sense oftaste is only one phase of the olfactory sense. We have not the slight-est conception as to how odor and taste stimuli in any animal act uponnerve endings to produce the various sensations of smell and taste
;
and as shown in the following pages, when bees are fed foods whichcontain undesirable substances emitting extremely weak odors, theyrefuse to eat the foods after " tasting " them. In view of the twopreceding facts we may call this perception an olfactory-gustatorysense, although the writer will endeavor to show that the gustatorysense plays no part in these responses.In the investigation herein recorded, two objects which throwconsiderable light on whether or not bees have a true gustatory sensehave been kept in view : ( 1 ) To determine whether bees have likes anddislikes in regard to foods, and (2) to make a careful study of themorphology of all the sense organs on the mouth-parts of the honeybee.
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—-McINDOO 3To obtain material for the study of the disposition of the senseorgans on the mouth-parts, adult specimens were used. In regard topreparing the specimens with caustic potash and to bleaching themwith chlorine gas, the reader is referred to the writer's work onHymenoptera (1914b, p. 295).To obtain material for the study of the internal anatomy of thesense organs herein discussed, worker pupa? 17 to 21 days old(counting from the time the eggs were laid) were mostly used, but afew adult worker bees were also employed. In regard to fixing thismaterial in Carnoy's fluid and to embedding it in celloidin and par-affin, the reader is referred to the writer's paper on Coleoptera ( 191 5,p. 409). The sections were cut from five to ten microns in thickness,and were stained with iron hematoxylin and eosin, safranin and gen-tian violet, and with Ehrlich's hematoxylin and eosin.All the drawings were made by the writer and all are originalexcept the internal anatomy of the mentum (Mt) in figure 10,which was copied from Snodgrass (1910). They were made at thebase of the microscope with the aid of a camera lucida.EXPERIMENTS TO DETERMINE WHETHER BEES HAVE LIKESAND DISLIKES IN REGARD TO FOODSThe writer (1914a) made a thorough study of the morphology andphysiology of the olfactory pores found on the wings, legs, and stingof the honey bee. At that time the same organs were seen on themouth-parts, but they were left for future study. Since the olfactorypores are so widely distributed, it is impossible to prevent all of themfrom functioning either by eliminating them by operations or bycovering them with a substance, because the more an insect ismutilated, the more abnormal its behavior becomes. This is particu-larly true when the mouth-parts are mutilated. When the appendagesare covered with liquid glue, vaseline, etc., bees do not eat until thesubstance is removed. When certain mouth-appendages are removed,bees are not entirely normal and their eating is more or less affected.Since it is impossible to eliminate the olfactory sense while deter-mining whether bees have a true gustatory sense, and as the varioussense organs on the mouth-parts cannot be mutilated without caus-ing considerable abnormality in the behavior of the bees while eating,it was decided to ascertain if bees have likes and dislikes in regard tofoods and to make a careful study of the morphology of all the senseorgans on the mouth-appendages in order to be able to judge whetheror not bees have a true sense of taste.
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i. Preliminary Experiments in Feeding Bees Foods ContainingVarious SubstancesTo determine the behavior of bees toward foods containing varioussubstances under conditions which permitted of their close observa-tion, triangular experimental cases were employed. These were madeof three narrow wooden strips, two of which were ten and the thirdsix inches long, each strip being an inch wide. Wire screen served asbottoms and tops for the cases whose apices and bases rested on sup-ports above a table near a window.Since cane-sugar candy is most conveniently fed to bees in ex-perimental cases, a quantity of this food was made by thoroughlykneading a good quality of confectioner's sugar with a small amountof honey. For convenience in handling it while feeding the bees, asmall lump of five grams, placed upon a small piece of cardboard,was put into each case.Sometimes it was necessary to feed the bees honey. This food waspoured into small tin feeders, each one being two and a quarter incheslong, one inch wide, and one-fourth inch deep. To prevent the beesfrom wasting the honey, fine parallel pieces of wire, one-eighth inchapart, were stretched lengthwise over the tops of the feeders.One drop of oil of peppermint was thoroughly mixed with 25 gramsof cane-sugar candy. This mixture was then divided into five equalparts. One hundred milligrams of quinine sulphate were also thor-oughly mixed with 25 grams of cane-sugar candy, and the mixturewas then divided into five equal parts.Twenty worker bees from the alighting-boards of various hiveswere introduced into each of five of the experimental cases, and theywere immediately fed the two foods just described and an equalamount of pure cane-sugar candy. The order of placing the foodsinto the cases was rotated so that case No. 1 received the pure cane-sugar candy first, the candy containing oil of peppermint second andthe candy containing quinine third. Case No. 2 received the candycontaining oil of peppermint first, the candy containing quininesecond and the pure cane-sugar candy third. Case No. 3 received thecandy containing the quinine first, the pure cane-sugar candy second,and the candy containing the oil of peppermint third. Cases Nos. 4 and5 were treated similarly. The order of arrangement of the candiesin the cases was also rotated so that no two cases contained the candiesin the same arrangement.When the pure cane-sugar candy was fed first, the bees covered itand ate greedily for several moments. When the candv containing
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOO 5
oil of peppermint was fed first, several bees ate greedily for only afew seconds, and when pure cane-sugar candy was given to them onlyoccasionally was a bee observed eating the candy containing oil ofpeppermint. When the candy containing quinine was fed first, manyof the bees ate greedily until the pure cane-sugar candy was givento them ; then they soon deserted the former for the latter. It was soonobserved that after eating 10 minutes, the bees were able to select thecandy they liked best ; therefore the first count was made 10 minutesafter giving them the first food and thereafter every 30 minutes. Inthese experiments, as in nearly all the others performed, 15 or morecounts were recorded, but since some of the substances fed cause agreater mortality than others, and in order to obtain a total averageas nearly uniform as possible, of the bees eating at any one count,only the first five counts have been considered. To ascertain if thedirection of the light was a factor in helping to select the food, thecases were often reversed end for end. After recording the numberof bees eating, they were often driven from a certain food by blowingupon them, but they invariably soon returned to the same food. Asa general rule for all the experiments performed, the longer the beeswere confined in the cases, the smaller was the number observed eat-ing at any given time. Neither the direction of the light nor thearrangement of the food in the cases is a factor in helping to selectthe foods they like best.The preceding set of experiments was repeated twice. As an aver-age for the 300 bees for five counts, 35.8 per cent of the bees wereseen eating pure cane-sugar candy, none eating candy containing oilof peppermint, and 2.3 per cent were observed eating candy containingquinine, making a total average of 38.1 per cent eating at any onecount. Twelve bees in case No. 4 of the first set of experiments beganto die when the fifth count was recorded. They had freely eaten thecandy containing quinine.Two days later three grams of chinquapin (Castanea pumila)honey were poured into each of five feeders. This food was thengiven to the bees used in the third set of experiments just described.During the first 15 minutes after introducing the honey, only sevenbees ate a little of it. After that they walked over the feeders, butnever offered to eat the honey again. This honey has a strong, char-acteristic, bitter odor. As an average for the 100 bees for five counts,15 minutes after introducing the honey 24.8 per cent were seen eatingpure cane-sugar candy at any one count, but none was noticed eating
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the candies containing oil of peppermint and quinine or the chinqua-pin honey.The following day honey containing oil of peppermint was substi-tuted for the chinquapin honey. This was had by mixing one dropof the oil of peppermint in 25 cubic centimeters of honey, and themixture was then divided into five equal parts. It emitted only a faintodor of peppermint, but when eaten by the writer the peppermintattribute was quite pronounced. It no longer tasted like honey.During the first five minutes only a few bees ate a little of it, andafter that none offered to eat it. As an average for the 100 bees forfive counts, 26.6 per cent were observed eating pure cane-sugar candyat any one count, but none was seen eating the candies and the honeycontaining oil of peppermint and quinine. Later the pure cane-sugarcandy in case No. 1 became exhausted, and instead of the bees select-ing either the candy or the honey containing oil of peppermint, theychose the candy containing quinine. For two hours they ate it asfreely as they previously had eaten the pure cane-sugar candy, butafter the third hour they ceased to eat it. By this time a few weredead and several were sick.One drop of cider vinegar was mixed with 25 grams of cane-sugarcandy and one drop of carbolic acid was mixed with an equal amountof cane-sugar candy. Each one of these mixtures was then dividedinto five equal parts. Fresh bees were introduced into the cases andwere fed pure cane-sugar candy and the mixtures just described. Asan average for the 100 bees for five counts, 17.4 per cent wereobserved eating pure cane-sugar candy, 28.8 per cent eating candycontaining vinegar, and 1 .4 per cent were seen eating candy contain-ing carbolic acid, making a total average of 47.6 per cent eating atany one count. The vinegar seemed to have brought about a chemicalchange in the candy and probably inverted the cane sugar. After thefifth count the bees ate this candy more freely than before.Two days later the candy containing vinegar was removed andcandy containing alum was placed in its exact position. The lattercandy was composed of one-half powdered alum, and the other halfof powdered sugar and honey. At first the bees ran over it, andthereafter only occasionally ate a little of it. As an average for the100 bees for five counts, 19.2 per cent were seen eating pure cane-sugar candy, 3.8 per cent eating candy containing carbolic acid, and3.4 per cent were seen eating candy containing alum, making a totalaverage of 26.4 per cent eating at any one count. The candy contain-ing carbolic acid at this time emitted only a faint odor.
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOOThe following day mannose (a monosaccharide or simple sugar)candy was given to the bees used in the preceding experiments. Thiscandy was made by kneading pure mannose (crystallized and washedtwice) and honey. For a few moments the bees in two cases seemedto like the mannose candy equally as well as the cane-sugar candy,although after a short time they became sick and later several died.As an average for the 100 bees for five counts, 24.2 per cent wereobserved eating pure cane-sugar candy, 0.2 per cent eating candy con-taining carbolic acid, none eating candy containing alum and 3.6 percent were seen eating mannose candy, making a total average of 28.1per cent eating at any one count.Fifteen grams of common salt (NaCl) were kneaded in honey.This mixture was then divided into five equal parts. It and chinqua-pin honey were fed to fresh bees. During the first 15 minutes thebees ate the salt containing honey rather freely, but seldom touchedthe chinquapin honey and after that seldom ate any of either food.Forty-five minutes after introducing the food, several bees in eachcase began to die. As an average for the 100 bees for five counts, 2.2per cent were seen eating chinquapin honey and 2 per cent eating saltcontaining honey, making a total average of 4.2 per cent eating at anyone count.The following is a tabulated summary of the preceding resultsobtained by feeding bees foods containing various substances. Thefigures in the third to tenth columns represent the average per cent ornumber of bees eating a particular food at any one count.TABLE IPreliminary Experiments in Feeding Bees Foods Containing VariousSubstances
T3
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65The preceding preliminary experiments clearly show the following
:
( 1) In regard to foods bees have likes and dislikes ; (2) before show-ing preferences between foods bees always eat more or less of themfirst, unless the foods contain strong repellents; (3) the longer thebees are confined in the experimental cases the less they eat, and (4)some of the substances fed are injurious to them. For the last tworeasons only the first five counts are sufficiently reliable for determin-ing the total average per cent of bees eating at any one count. Theseexperiments indicate that bees may have a sense of taste, becauseneither the direction of the light nor the arrangement of the food inthe cases helps in selecting the food they like best, and the olfactorysense may not be the sole factor in selecting foods, for bees mustusually eat more or less of them before being able to show preferencesbetween them. It is probable that bees cease eating some foodsbecause their alimentary tracts may be affected, and for this reasonalone they may reject the particular food that does not agree withthem.The preceding results suggest five classes of foods to be used in thefollowing experiments. Foods containing strong repellents may beemployed to determine the importance of the olfactory sense in caus-ing bees to avoid such substances, and foods containing sweet, bitter,sour, and salty substances may be used to ascertain if bees show pref-erences between foods having the four attributes of human taste.
2, Experiments in Feeding Bees Foods Containing RepellentsPure cane-sugar and candy containing oil of peppermint (de-scribed above, page 4) were fed to fresh bees in the cases asdescribed in the preceding pages. After waiting 10 minutes the firstcount was recorded, and thereafter every 30 minutes. As an averagefor the 100 bees for five counts, 35.4 per cent were seen eating thepure cane-sugar candy at any one count, while they never touched thecandy containing oil of peppermint.The preceding was repeated by feeding candy containing carbolicacid (described on p. 6) and pure cane-sugar candy to fresh bees.As an average for the 100 bees for five counts, 41.4 per cent were seeneating pure cane-sugar at any one count, while none touched thecandy containing carbolic acid.The preceding was repeated by feeding pure honey and honeycontaining whiskey to fresh bees. Four grams of pure honey were
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 9poured into each of five feeders, and the same amount containing threedrops of whiskey was likewise poured into each of five other feeders.The odor of whiskey from the latter food was not pronounced tothe writer, but the taste of whiskey was quite pronounced. Whenthese foods were introduced into the cases the bees ate one as freelyas the other. Five minutes after feeding them the first count wastaken and thereafter every five minutes. Since it takes bees confinedin these cases only 10 to 15 minutes to fill their honey stomachs withliquid foods, only two counts were taken. As an average for the 100bees for two counts, 30 per cent were seen eating pure honey and 22per cent eating honey containing whiskey, making 52 per cent eatingat any one count.A mixture of 25 cubic centimeters of honey and two drops of car-bolic acid was divided into five equal parts, each part being fed to 20fresh bees in the usual manner. For the first 15 minutes after intro-ducing the food, the bees avoided it, but later a few ate it to a lim-ited degree. As an average for the 100 bees for five counts, 3 percent were seen eating it at any one count. Nine days later this honeydid not emit such a strong carbolic-acid odor. It was again fed tobees. Only two counts were taken. As an average for the 100 bees,27.5 per cent were seen eating at any one count.The preceding was repeated by feeding honey containing oil ofpeppermint (described on p. 4) to fresh bees. As long as the mix-ture emitted a strong odor of peppermint the bees avoided it, butnine days after preparing the mixture the bees ate it rather freely.As an average for the 100 bees, 27.5 per cent were seen eating it at anyone count.Twenty-five cubic centimeters of honey were mixed with two dropsof each of the following: formic acid, sulphuric acid, xylol, formal-dehyde, kerosene, and lime-sulphur. The bees usually avoided thesemixtures, but occasionally one or two offered to eat a little of thefood. The first count was recorded 30 minutes after introducing thefood and thereafter every hour. As an average for the 100 bees ineach set of experiments for five counts, the following numbers repre-sent the bees seen eating at any one count : Formic acid—-7.4 per cent,sulphuric acid—4.2 per cent, xylol—5.2 per cent, formaldehyde
—
3.2 per cent, kerosene—1.6 per cent, and lime-sulphur—1.2 per cent.The following is a tabulated summary of the preceding resultsobtained by feeding bees foods containing repellents. The figures
IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65in the third to fourteenth columns represent the average per cent ornumber of bees eating a particular food at any one count.TABLE II
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO IIMannose, which appears to be almost as sweet as saccharine, has adisagreeable, bitter-sweet taste. Each one of these sugars has its ownfaint, characteristic odor, but the predominating odor emitted fromthe candy made of each is that of honey. To the writer the starchcandy gave off only one faint odor, that of honey. Dextrine is lightyellow and emits a stronger odor than does any one of the sugars.Twenty fresh bees were introduced into each of five cases. Whenthe preceding nine candies were put into the cases, the bees wanderedabout considerably and ate a little of each candy, but ate the mannoseand levulose most greedily. A short time after eating the mannose,many of the bees began to die. Thirty minutes after feeding the bees,the first count was taken, and thereafter every half hour. The fourcounts recorded showed that only one bee was seen eating mannose,four eating levulose and none eating any of the other candies. Thissmall number is certainly due to most of the bees soon becoming sickand some dying.The preceding experiments were repeated by feeding cane-sugar(saccharose) , saccharine, mannose and levulose candies to fresh bees.As usual the bees wandered about considerably and ate a little of eachcandy except the saccharine. An hour later those that had eaten themannose became sick and ate no more that day, but the next morningmost of them had recovered and a few were seen eating a little. Asa total for the 100 bees for 17 counts, 10.7 per cent were seen eatingcane-sugar, 6 per cent eating levulose, 1 per cent eating saccharineand none eating mannose candy.To ascertain if bees could be forced to eat saccharine, fresh beesand a lump of the saccharine candy were put into each of the five cases.The bees perched upon and ran over the candy as if it were a piece ofwood. It neither repelled nor attracted them, and during an entirehour only five bees licked the candy for a few seconds. The starchcandy was next tried alone. During the first ten minutes severalbees ate it rather freely, but after that for an hour only occasionallydid a bee eat a little of it.Cane-sugar, dextrose, dextrine and raffinose candies were put intoeach case, and fresh bees were employed as usual. As an average forthe 100 bees for five counts, 41.2 per cent were seen eating cane-sugar,2.6 per cent eating dextrose, none eating dextrine and 0.2 per centeating raffinose candy, making a total average of 44 per cent eatingat any one count.Levulose, dextrose and raffinose candies were next used. As anaverage for the 100 bees for five counts, 20 per cent were seen eating
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65levulose, none eating dextrose and 1 .8 per cent eating raffinose candy,making a total average of 21.8 per cent eating at any one count.Dextrose, raffinose and dextrine candies were used in the same way.As an average for the 100 bees for five counts, 21 per cent were seeneating raffinose, 12 per cent eating dextrose and 6.8 per cent eatingdextrine candy, making a total average of 39.8 per cent eating at anyone count.Dextrine, lactose and maltose candies were used in the same way.As an average for the 100 bees for five counts, 42 per cent wereobserved eating maltose candy at any one count, but none was seeneating lactose or dextrine candy.The preferences shown between these candies may have been par-tially due to the amount of water in them. No two of these candiesabsorbed the same amount of water vapor from the air, but duringthe first day the water in any of them was not noticeable, althoughafter that it was quite noticeable. Levulose absorbed the most watervapor and saccharine the least.Dextrose, raffinose and maltose candies were next used. As anaverage for the 100 bees for five counts, 16 per cent were seen eatingmaltose, 12 per cent eating raffinose and 7 per cent eating dextrosecandy, making a total average of 35 per cent eating at any one count.To ascertain if bees show preferences between honeys, an equalamount of light-colored honey and dark-colored honey was pouredinto each of five feeders. Perhaps most of the light-colored honeycame from basswood trees, while the source of the dark-colored honeywas unknown. The latter honey was taken in the crystallized formfrom old combs and was then melted. The odors and tastes of thesetwo honeys were quite different. Fresh bees from the alighting-boards were introduced into the cases, and during the first five minutesafter giving them the two honeys, they ate each one greedily. By thetime they had eaten five minutes, most of them had selected the honeythey liked the better. At this stage the ones eating were counted,and five minutes later were counted again. After this few were seeneating, because nearly all of them by this time had filled their honeystomachs. This set of experiments was repeated twice. As an aver-age for the 300 bees for two counts, 24.3 per cent were seen eating thelight-colored honey and 18,8 per cent the dark-colored honey, makinga total average of 43.1 per cent eating at any one count.Fresh bees were placed in the cases, and they were fed light-colored honey and sugar syrup (half sugar and half water) in thesame manner as just described. As an average for the 100 bees for
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 13two counts, 37 per cent were seen eating the honey and 4 per centthe syrup, making- a total average of 41 per cent eating at any onecount.In the same manner light-colored honey and pollen mixed thor-oughly with light-colored honey (1 part pollen to 4 parts honey) weregiven to fresh bees. As an average for the ioo.bees for three counts,26.3 per cent were seen eating the light-colored honey and 16.3 percent the honey mixed with pollen, making a total average of 42.6 percent eating at any one time.In the same way light-colored honey, and sugar mixed with light-colored honey (half and half) were fed to bees. As an average forthe 100 bees for five counts, 30.4 per cent were seen eating the honeyand 11 per cent the mixture of sugar and honey, making a totalaverage of 41.4 per cent eating at any one count. Since one of thesefoods was a thick paste, five counts were recorded before the beesceased eating, while in the experiments just preceding only threecounts were necessary, because the mixture of pollen and honey madea thin paste.The following is a tabulated summary of the preceding resultsobtained by feeding bees sweet foods. The figures in the third tofourteenth columns represent the average per cent or number of beeseating a particular food at any one time.TABLE IIIExperiments in Feeding Bees Sweet Foods
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4. Experiments in Feeding Bees Foods Containing BitterSubstancesTwo lots of 25 grams of cane-sugar candy each were thoroughlymixed, one with 500 milligrams of finely pulverized quinine sulphateand the other with a like quantity of strychnine sulphate. Eachmixture was then divided into five equal parts. To the writer theodor from each mixture was exactly like that from pure cane-sugarcandy, although the human nose is able to detect a faint odor emittedfrom a large quantity of either quinine or strychnine. Strychnine isregarded as the bitterest of all substances. To the writer both of thesemixtures were extremely bitter. Equal amounts of pure cane-sugarcandy and of these other two foods were fed to fresh bees in theusual manner. Five minutes after introducing the foods, the firstcount was taken and thereafter every 15 minutes. As an average forthe 100 bees for five counts, 47.4 per cent were observed eating purecane-sugar candy, 5.8 per cent eating candy containing quinine, and 4per cent eating candy containing strychnine, making a total averageof 57.8 per cent eating at any one count.These experiments were repeated by feeding fresh bees only thecandies containing quinine and strychnine. As an average for the100 bees for five counts, 39.4 per cent were seen eating candy con-taining quinine and 4 per cent eating candy containing strychnine,making a total average of 43.4 per cent eating at any one count. Anhour after introducing the foods, the bees began to die.Twenty-five grams of cane-sugar candy were mixed with 500 milli-grams of liquid picric acid, and then the mixture was divided into fiveequal parts. This food was almost as bitter as quinine and emitteda faint odor, different from that of pure cane-sugar candy. Thepreceding experiments were repeated by feeding fresh bees thismixture, candy containing quinine and pure cane-sugar candy. As anaverage for the 100 bees for five counts, 19.2 per cent were seen eatingpure cane-sugar candy, 34.4 per cent eating candy containing picricacid and 2.2 per cent eating candy containing quinine, making a totalaverage of 55.8 per cent eating at any one count.The preceding was repeated by using the same amount of powderedpicric acid instead of the liquid picric acid and by discarding the candycontaining quinine. As an average for the 100 bees for five counts,45 per cent were observed eating pure cane-sugar candy and 1 percent eating candy containing picric acid, making a total average of 46per cent eating at any one count.
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOOThe experiments just described were repeated by making a candy ofpowdered picric acid and honey. As an average for the 100 bees forfive counts, 45 per cent were seen eating the pure cane-sugar candyat any one count, but none ate the candy made of picric acid and honey.Judging from the three sets of experiments in which picric acid wasused, it seems that this acid in the liquid form effects a chemicalchange in cane sugar, thereby causing bees to prefer candy mixedwith it to pure cane-sugar candy.Chinquapin honey, which has a bitter taste, was next fed to beesas described on page 5. As an average for the 100 bees for sevencounts, only 3.4 per cent were seen eating at any one count.The following is a tabulated summary of the preceding resultsobtained by feeding bees foods containing bitter substances. Thefigures in the third to ninth columns represent the average per centor number of bees eating a particular food at any one count.TABLE IVExperiments in Feeding Bees Foods Containing Bitter Substances
•e
i6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
average for the 100 bees for two counts, 26.5 per cent were observedeating pure honey and 17 per cent eating honey containing lemonjuice, making a total of 43.5 per cent eating at any one count.The preceding was repeated by using three drops of acetic acid(99.5 per cent) in each feeder containing four grams of honey. Theacid made the honey quite sour and changed its odor slightly. Asan average for the 100 bees for two counts, 28 per cent were seeneating pure honey and 5.5 per cent eating honey containing aceticacid, making 33.5 per cent eating at any one count.Hydrochloric acid (37 per cent) was used in the same manner. Itslightly changed the odor of the honey and gave it a sharp, sour taste.As an average for the 100 bees for two counts, 50 per cent were ob-served eating pure honey at each count, but none ate the honey con-taining acid.Sulphuric acid (95 per cent) was next used in the same manner.This acid gave the honey a less sharp, sour taste than did hydro-chloric acid. As an average for the 100 bees for two counts, 28.5per cent were seen eating pure honey at each count, while none ate thehoney containing acid.Nitric acid (68 per cent) was employed in the same way. This acidgave the honey a sour taste, although not sharp. As an average forthe 100 bees for two counts, 33.5 per cent were observed eating purehoney at each count, while none ate the honey containing acid.The following is a tabulated summary of the preceding results ob-tained by feeding bees foods containing sour substances. Thefigures in the third to eighth columns represent the average per centor number of bees eating a particular food at any one count.TABLE VExperiments in Feeding Bees Foods Containing Sour Substances
•a
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOO \JJudging from the above table, it is seen that bees prefer pure honeyto honeys containing sour substances.
6. Experiments in Feeding Bees Foods Containing SodiumSaltsFive lots, each containing 15 grams of cane-sugar candy, were eachthoroughly mixed respectively with 500 milligrams of the followingfinely pulverized and chemically pure salts : sodium chloride (commonsalt), sodium sulphite, sodium nitrate, sodium carbonate and sodiumfluoride. Each one of these mixtures was then divided into five equalparts. Each of the salts used has a faint odor and no two have odorsalike, and the odor of each mixture was slightly different from that ofpure candy. The taste of the mixture containing sodium chloride wasslightly salty and the tastes of the other mixtures were more or lessdifferent from that of pure candy ; no two were alike and none wasexactly salty. Sodium fluoride has a sharp, astringent taste and seemsto burn the mucous membrane. Some of the mixtures absorbed morewater vapor from the air than others and some changed slightly incolor. All five mixtures and pure cane-sugar candy were fed to freshbees in the usual manner. At first the bees ate a little of each candy,and before having time to select the ones they liked best, many beesbecame sick and soon began to die.Pure cane-sugar candy and the candy containing sodium chloridewere tried alone. Since all these salts were more or less injurious tobees, the first count was made five minutes after introducing the foodand thereafter every 15 minutes. As an average for the 100 beesfor five counts, 39.6 per cent were seen eating pure cane-sugar candyand 5.8 per cent eating the candy containing sodium chloride, makinga total average of 45.4 per cent eating at any one count.The candies containing sodium carbonate and sodium sulphite weretried alone. As an average for the 100 bees for five counts, 9 per centwere observed eating the latter mixture, but only 0.6 per cent eatingthe former mixture, making a total average of 9.6 per cent eating atany one count. A half hour after introducing the food, many beeswere sick and a half hour still later several were dead.The mixture containing sodium nitrate and sodium fluoride werenext tried alone. As an average for the 100 bees for five counts, 2.2per cent were seen eating the latter mixture and 9.6 per cent eatingthe former mixture, making a total average of 11.8 per cent eatingat any one count. A half hour after feeding the bees, many becamesick and soon began to die.
i8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65Pure cane-sugar candy and the mixture containing sodium car-bonate were fed alone. As an average for the 100 bees for fivecounts, 56.6 per cent were observed eating pure cane-sugar candy atany one count, while none ate the mixture containing sodium car-bonate.Pure cane-sugar candy and the mixture containing sodium sul-phite were also fed alone. As an average for the ioo bees for fivecounts, 52.2 per cent were seen eating pure cane-sugar candy and3.2 per cent eating the mixture containing sodium sulphite, making atotal average of 55.4 per cent eating at any one count. An hour afterintroducing the food, a few bees became sick.Pure cane-sugar candy and the mixture containing sodium nitratewere likewise fed alone. As an average for the 100 bees for fivecounts, 45.6 per cent were seen eating pure cane-sugar candy and 3.8per cent eating the mixture containing sodium nitrate, making a totalaverage of 49.4 per cent eating at any one count.Pure cane-sugar candy and the mixture containing sodium fluoridewere fed last. As an average for the 100 bees for five counts, 32.2per cent were observed eating pure cane-sugar candy and only 0.4per cent eating the mixture containing sodium fluoride, making a totalaverage of 32.6 per cent eating at any one count. A half hour afterintroducing the food, several bees became sick.The following is a tabulated summary of the preceding resultsobtained by feeding bees foods containing sodium salts. The figuresin the third to eighth columns represent the average per cent or num-ber of bees eating a particular food at any one count.TABLE VIExperiments in Feeding Bees Foods Containing Sodium Salts
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 19.Judging from the above table, it is seen that bees prefer pure cane-sugar candy to any one of the above foods containing sodium salts,and that they show preferences between these various mixtures.
7. Experiments in Feeding Bees Foods Containing PotassiumSaltsThe preceding experiments were repeated by using potassiumbromide, potassium carbonate, potassium cyanide, potassium ferro-cyanide, potassium iodide, and potassium nitrate. When potassiumbromide, potassium ferrocyanide, and potassium nitrate were mixedTABLE VIIExperiments in Feeding Bees Foods Containing Potassium Salts
20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
almost ceased eating. They wholly refused to eat candy contain-ing" potassium cyanide but freely ate the mixture containing' potas-sium ferrocyanide, and this salt apparently did not affect them. Adetailed account of these experiments is not necessary, because theresults are similar to those when the sodium salts were used.Table VII is a tabulated summary of the results obtained byfeeding bees with foods containing potassium salts. The figures inthe third to ninth columns represent the average per cent or numberof bees eating a particular food at any one count.It is evident from the above tabulated results that bees prefer purecane-sugar candy to the mixtures containing potassium salts, and thatthey also show preferences between foods containing these salts.
8. Summary of Preceding ExperimentsThe preceding results clearly demonstrate that bees have likes anddislikes in regard to foods, and it seems that their faculty to dis-criminate between foods is more highly developed than ours, becausethey can distinguish differences between the foods fed to them betterthan the writer. The candies containing strychnine and quinine bestillustrate this point. Equal amounts of these two bitter salts wereused ; but when the writer tasted the candies containing them, little orno difference in bitterness could be detected, although, judging fromthe number of bees that ate them when the two foods were fed alone,the bees distinguished a marked difference between them.As a general rule, foods agreeable to us are also agreeable tobees, but there are a few . marked exceptions. All foods scentedwith peppermint are pleasant to us, but repellent to bees. The writerdoes not care for candy containing potassium ferrocyanide, but beesare rather fond of it, and it does not seem harmful to them.In regard to the repellents used, the few experiments performeddo not warrant definite deductions, but the results indicate that lime-sulphur and kerosene are the strongest of the repellents used, whileformic acid repels the least and carbolic acid the most among theacids. That the acids as a rule are not better repellents may pos-sibly be explained by the fact that bees are more or less accustomedto the odors from the acids found in their foods and varioussecretions.The results obtained demonstrate that bees like honey best of allfoods and that they are able to distinguish marked differences be-tween various kinds of honeys. Substitutes for honey as food forbees may be better than honey in a few instances, but these investi-
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—MdNDOO 21gations indicate that no substitute can be had which will be likedby bees as well as the best pure honey.The fact that bees must first eat more or less of the foods beforebeing able to discriminate differences between them, unless they con-tain repellents, indicates that bees have a true gustatory sense, pro-viding this discrimination is not accomplished by means of theolfactory sense. Since this point cannot be determined experi-mentally, our only criterion is to make a thorough study of all thesense organs on and near the mouth-parts. This part of the work isgiven in the following pages.MORPHOLOGY OF THE SENSE ORGANS ON THE MOUTH-PARTSOF THE HONEY BEEIn the preceding pages it is stated that bees show preferencesbetween foods. In order that they may show preferences betweenthe foods emitting weak odors, it is first necessary for them to eata little of the foods. This fact indicates that bees may have a truesense of taste. If the mouth-parts possess sense organs which areanatomically fitted for receiving gustatory stimuli, we are safe insaying that bees can taste. In order to find such organs, if possible,it was necessary to make a special study of all the sense organs on andnear the mouth-parts. In order to distinguish the sense organs fromother structures on the mouth-parts, the internal anatomy of all thestructures on the integument was first studied. This was accom-plished by making many transverse and longitudinal sections throughall parts of the mouth-appendages and even through the entire head.Only two general types of sense organs were found; 'viz.: inner-vated hairs and innervated pores.Hairs on the honey bee are of two kinds—branched or barbed hairsand unbranched ones. As far as known the branched ones are neverinnervated and are never found on the mouth-appendages, but onthe head near the mouth-parts and elsewhere. The unbranchedhairs not only occur on the mouth-appendages but also on the otherparts of the integument, although most abundantly on the mouth-parts and compound eyes. They may or may not be innervated.All true hairs, whether branched or unbranched, arise from hairsockets (fig. 2 Q, HrSk) whose cavities (SkCav) communicate withthe lumens (L) of the appendages and with the cavities (HrCav)of the hairs. The long hairlike structures (fig. 3 A. Hr1 ) on thetongue or glossa may be called pseudo-hairs, because they are merely
2.2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65prolongations of the chitin. They do not arise from sockets, are nothollow and do not communicate with the lumen (L) of the tongue.The spoon-shaped lobe, the labellum (fig. 7, Lbl) forming the tipof the tongue, is also covered with pseudo-hairs. These are short andthick and are branched at their tips, while those on the tongue arelong and slender and are unbranched. Several minute pseudo-hairsare also present on the dorsal side of the mentum (fig. 7, Mt) andelsewhere on various parts of the integument.The writer in 19 14 made a study of the innervated pores (calledolfactory pores) found on the wings, legs, and sting of the honey bee.
Fig. 1.—Internal anatomy of varieties a and b of spinelike, innervated hairsof worker honey bees, x 580. A, variety a on epipharynx (figs. 9 A and 10, Ep).B, C, D and E, variety b: bi from outer surface at proximal end of mandible(fig. 7, Md), bi from inner surface at distal end of mandible (fig. 8, Md), b3from pharyngeal plate (figs. 9 B and 10, PhPl), and bi from outer surface attip of mandible (fig. 7, Md). C from 17-day-old pupa, B and E from 20-day-oldpupae, and A and D from 21-day-old pupse. The nerve (iVs) in D is taken froma deeper focus than the other parts in the figure. See page 54 for explanationof abbreviations.At that time he also saw the same pores on the mouth-parts, andsince then has seen a few on each antenna near its articulation withthe head.
1. Structure of the Innervated HairsInnervated hairs may be roughly divided into spinelike and peglikehairs, although there is no sharp dividing line between the two classes.The different varieties of these two classes vary gradually from long,slender hairs to short, stubby ones. For description the varieties maybe designated alphabetically.
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 23(a) SPINELIKE HAIRSVariety a. In describing the spinelike hairs we shall begin withthe most delicate ones and then proceed toward the largest, andwe shall carefully examine the anatomy of each variety to ascertainif it is anatomically adapted for receiving odor stimuli.In regard to the thickness of the walls, the most delicate varietyis found on the epipharynx (figs. 9 A and 10, Ep). These are nottypically true hairs, because they do not arise from hair sockets, butfrom small cones (fig. i A, Con^ which, however, might be regardedas another type of sockets. Of all the hairs, these have the thinnestwalls. The walls become gradually thinner from the bases to thetips. These hairs are so small and so light in color that they are easilyoverlooked. Each one arises from the summit of a small cone whosewalls are thick and are dark in color, while the chitin (Chx ) betweenthe cones is light in color. Chitin is stained little or not at all withEhrlich's hematoxylin. Flexible chitin is usually light in color, -andwhen chitin is not flexible it is generally dark in color. For this reasonthese hairs cannot be bent at their bases but may be bent near theirtips; and likewise the cones, which project slightly above the levelof the surrounding chitin, are rigid, but since the surrounding chitinis flexible each cone with its hair has considerable freedom of motion.In most cross-sections through the epipharynx showing these hairsthe sense cells are grouped together so closely that each hair seemsto be provided with either a multinucleated sense cell or with morethan one cell, each having only one nucleus. In extremely thin sec-tions where the sense cells are not piled upon one another, however,it is clearly seen that each hair is innervated by a single sense cell(fig. 1 A, SC) having only one nucleus (SCNuc) . In the 21-day-oldpupa the hypodermis (Hyp) is comparatively thin.Wolff (1875) regarded these cones with their hairs as having anolfactory function, and according to their anatomy they are adaptedequally as well for gustatory organs, but since chitin after onceformed is dead matter and is not porous, it does not seem reasonableto think of either odoriferous particles or liquid foods being ableto pass into the hairs in order that the nerves may be stimulated, evenif the walls of these hairs are extremely thin.Variety b. This variety is found on the mandibles (figs. 7, 8, and6 B, b t , b 2 and fc 4 ) and on the pharyngeal plate (figs. 9 B and 10, & 8 ).These are short, stout hairs with thick walls. At the proximal end ofthe mandible (fig. 7, b x ) they are usually bent and about a half of eachone lies buried in the chitin surrounding the socket (fig. 1 B, bj.
24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65The chitin (Ch) at this place is extremely thick, causing the sensefibers (SF) to be very long. In all sections passing through thisgroup of hairs the sense cells (SC) are discernible, but their fibersare usually severed because an entire cell rarely lies in the same planein which the section was cut. In the 20-day-old pupa the hypodermis(Hyp) is comparatively thin.On the ventral side of the mandible (fig. 8, b 2 ) these hairs arestraight, but have the same structure as the ones just described,except that the sockets (fig. I C) are sunk only slightly beneath theouter surface of the chitin.Those on the pharyngeal plate (fig. 1 D, b 3 ) are slightly larger thanthe ones just described. These are slightly curved and most of thempoint toward the mouth. Their sockets stand a little above the levelof the chitin, and the walls at their tips are not so thick as at thebases. The sense fibers run nearly all the way to the tips of the hairs.Beneath the pharyngeal plate in the 21 -day-old pupse, the hypodermis(Hyp) is extremely thick and its cells are so grouped together thateach hair seems to be innervated by a large group of cells, but in allsuch cases no sense fibers were seen running from the groups to thehairs. After spending considerable time it was ascertained that thesense cells (SC) seldom lie in the middle of the hypodermis, but nearits inner edge. They are usually cut transversely, and for this reasonthe fibers are rarely seen connecting with the cell bodies.The hairs (figs. 1 E and 7, &4 ) at the distal ends of the mandiblesare the longest ones of this variety, and their tips are blunt, whilethe tips of the others are sharp. In structure they are like those onthe ventral side of the mandibles (fig. 1 C, b 2 ), except that they areslightly curved.Variety c. This variety, found on the head and all the head appen-dages, varies from the smallest hairs on the antennae (fig. 2 A) to thelargest on the maxillae (fig. 2 U). Figure 2 A and B represent thesmallest and largest on the flagellum of a worker bee, and figure 2 Cthose on the scape. All of those on the maxillae are of about the samesize (fig. 2 D and E), but when first observed those on the maxillarypalpi (fig. 2 E) appear to be the smallest. Those on the labial palpi(fig. 2 F) are slightly larger than those on the maxillae. Those on themandibles (fig. 2 G) and paraglossae (fig. 2 H) are of the samesize and are considerably larger than the ones just described. On thecervical plate (fig. 10, CvPl) these hairs (fig. 2 I to K) vary con-siderably in size. Just inside the buccal cavity a few innervated hairs(fig. 2 L) were found; also a few (fig. 2 M) on the head near the
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOO 25
Fig. 2.—Internal anatomy of variety c of spinelike, innervated hairs of workerhoney bees, x 580. A, smallest and B, largest of these on flagella of antennae
;
C from base of scape of flagellum ; D from maxilla; E from maxillary palpus;F from labial palpus ; G from proximal end of mandible ; H from base of para-glossa; I to K from cervical plate; L from just inside buccal cavity; M fromside of head, near base of mandible ; N from median line on top of head, overpharyngeal plate; O from palpiger; P from side of mentum; Q from middle ofglossa, the hair being from a whole mount and the hair socket (HrSk) fromsection ; R from tip of glossa ; S from dorsal and T from ventral surface oflabrum ; U from tip of maxilla. All of these hairs, except ci to c3 , may be locatedby referring to figures 7, 8, 9 C and 10. They were taken from pupa and imagoworkers of various ages. See page 54 for explanation of abbreviations.
26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65base of the mandibles, and a few (fig. 2 N) on top of the head directly-above the pharyngeal plate (fig. 10). The following figures repre-sent the innervated hairs found in sections through the palpigers(figs. 2 O, 7, Pig) ; on the side of the mentum (figs. 2 P, 7, c15 ) ; onthe glossa (fig. 2 Q and R) ; on the labrum (fig. 2 S and T) ; and onthe labial palpi and maxillae (fig. 2 U).In structure these various hairs are all alike in that they have thickAvails, sharp points and distinct sockets. The sockets of the smallerhairs usually lie slightly beneath the external surface of the chitin,as shown in figure 2 D, while those of the larger hairs may lie a littlebeneath the external surface of the chitin, as seen in figure 2 G, orabove the surface of the chitin, as shown in figure 2 Q. The chitin con-necting the base of the hair with the socket is always more or less
Fig. 3.—Cross-sections through glossa or tongue of a worker honey bee,showing internal anatomy including groove (Gv), canal (Can) inside rod (R),sense cells (SC), nerve (JVi), trachea (Tr) ; lumen (L), and bases of pseudo-hairs (Hr1 to Hr*) and innervated hairs (cw ), x 230. A, through middle and Bthrough tip of glossa.flexible, so that the least movement of the hair mechanically irritatesthe end of the sense fiber.The sense cells belonging to all the hairs drawn were not seen, butthe sense fibers were seen as shown. A hair was never regarded asense organ unless a sense fiber was seen running into it. The sensecells are always spindle-shaped and the sense fibers (fig. 2 H, SF)never run far into the hairs.The hairs at the tip of the tongue of the honey bee (fig. 7, Gls)have been regarded as gustatory in function, but as yet no one hasever shown that they are innervated. In cross-sections through themiddle of the tongue the sense cells (fig. 2 Q, SC) are generally dis-cernible, but owing to the poor fixation only traces of them may beseen in the tip of the tongue, although the sense fibers (fig. 2 R, SF)are usually visible. On either side of the tongue a nerve (fig. 2 Q,Nx ) and a trachea (Tr) are always present. They lie side by sideand are fastened together with connective tissue. Branches from
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 27the nerve are given off now and then which run toward the sense cells,but the actual connection of them with the cells was not observed.The internal anatomy of the tongue is best understood by referringto the semidiagrammatic figure 3 A and B. Figure 3 A is through themiddle of the tongue, while 3 B is through the tip.(b) PEGLIKE HAIRSTwo varieties of peg-shaped hairs occur on the maxillae and labialpalpi. To compare them with those found on the antennas, two of thelatter have been drawn.Variety d. Figure 4 A and B represent the smallest and largestpegs seen on the flagellum of a worker bee. The chitin at the tips isabout as thick as elsewhere. Other observers state that the chitin atthe tips of these hairs is much thinner than elsewhere. This is ap--
Fig. 4.—Internal anatomy of varieties d, e and / of peglike, innervated hairsof worker honey bees, x 580. A, smallest and B, largest of pegs on flagella ofantennae ; C from maxilla ; D from labial palpus ; E from outer surface neartip of maxilla. These hairs, except di and dz, may be located by referring tofigures 7 and 8.parently true when a bright light is used, for the chitin is so nearlytransparent at the tip that it appears thinner than where it is darker.When these hairs are carefully observed through the highest lensesand with less light, it seen that the chitin at their tips is about as thickas at their bases.Variety e. The peglike hairs on the maxillae (figs. 4 C, 7 and 8, e^)and labial palpi (4 D and 8, e2 ) are similar in structure to those onthe antennae. The following slight differences may be pointed out.Those on the mouth-parts are never so large as those on the antennae.Their tips are less blunt and their sockets project slightly above thesurface of the chitin, while the sockets of those on the antennae lie alittle below the external surface of the chitin.Variety f. These are found on the distal ends of the maxillae andlabial palpi (figs. 7 and 8, /). They are long and slender, usually
28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
slightly curved, and have blunt tips (fig. 4 E) . The chitin of the distalhalf of the maxilla contains many long longitudinal and deep grooves(fig. 4 E, Gv). These grooves cause the wide maxillary lobe to bequite flexible, thus enabling the bee to fold the maxillae around theother mouth-parts.Judging from the anatomy of all the spinelike and peglike hairsdescribed in the preceding pages, it does not seem possible that theycan serve either as gustatory or as olfactory organs because theodoriferous particles in the air and the liquids carrying substances insolution could not pass through the hard and thick walls of the hairsto stimulate the ends of the nerves. Since insects cannot feel weakmechanical stimuli through their chitinous integuments without somekind of a sensory organ, it seems that all of these innervated hairs arewell adapted to serve as tactile organs. The sense of touch is furtherdiscussed on page 39.
2. Structure of the Olfactory PoresOlfactory pores were found on the mandibles (figs. 7 and 8, Md,For), maxilla? (fig. 8, Mx), labial palpi (fig. 7, LbPlp), tongue (fig.7, Gls) , side of head, in the buccal cavity, on the cervical plate and onthe bases of the scapes of the antennae. In structure all of these aresimilar, and they are identical with those which have already beenfound on the legs, wings and sting.Figure 5 A represents one of the largest olfactory pores found onthe mandibles. The chitin (Ch) of the mandibles is always verythick, making the necks (fig. 5 E, NkFl) of the small pores long andslender. A chitinous cone (fig. 5 A, Con) is always present. Inpupae these cones are usually connected with a hypodermal secretion(HypS), but in adults this secretion is never seen. Sometimes thissecretion fills the entire pore, and it generally contains streaks run-ning from the hypodermis (Hyp) to the cone. Unless all stagesof these organs are critically studied, it is easy to imagine thatthis secretion is a permanent structure of the pores. This ex-plains why Janet (1911) regards this substance as a part of theorgan, and why he thinks that the cavity of the pore is filled withtwo or three concentric cylinders. In studying the same organsin Coleoptera, the writer (1915, p. 422) shows that the cones are alater formation than the chitin surrounding them and that the hypo-dermal secretion does not begin to form the cones until the sense fibershave connected with the pore apertures. The writer has also shown
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOO 29
that the sense cells begin to differentiate when the hypodermal cellsbegin to form the chitin. It is thus seen that by the time the chitin isof considerable thickness, the sense fibers have united with the poreapertures and the formation of the cones has begun. There are twopossible functions of the cones : (1) to strengthen the chitin formingthe bottoms of the flask-shaped pores, and (2) to insure firm attach-ments for the peripheral ends of the sense fibers. The latter function
Fig. 5.—Internal anatomy and superficial appearance of olfactory pores onmouth-parts, head and cervical plate of worker. honey bees, x 580. A to F,cross-sections ; A, one of largest olfactory pores from mandible of a 20-day-oldpupa, showing sense cell (SC), pore aperture (PorAp), and hypodermalsecretion (HypS) forming the cone (Con) ; B, two olfactory pores and onesense cell from base of glossa ; C, three olfactory pores and one sense cell frommaxilla; D, a group of olfactory pores and sense cells in labial palpus ; E, anolfactory pore from side of head ; F, two olfactory pores from buccal cavity
;
G to K, superficial appearances : G, three of largest olfactory pores on man-dible ; H, one of the two groups of olfactory pores on base of tongue ; I, groupof olfactory pores on maxilla ; J, group of olfactory pores on labial palpus ; K,three of largest olfactory pores on cervical plate. These pores may be locatedby referring to figures 7, 8, 9 C and 10. See page 54 for explanation ofabbreviations.
30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
seems absolutely necessary for the following reason. In adult bees thehypodermis is quite thin and in certain places has practically disap-peared. It no longer is firmly fastened to the chitin and it can nolonger hold the sense cells in their proper places. If the sense fiberswere fastened to the chitin only by the ends of their walls and not bythe entire peripheral ends being surrounded by the chitinous cones,the sense fibers would break loose from the pore apertures. Firmattachments for the sense fibers in spiders (Mclndoo, 191 1) are notnecessary, because the sense cells lie in a thick hypodermis which per-sists throughout the lives of the spiders ; and furthermore, cones arenot formed, because the pore apertures pass entirely through thecuticula, so that the sense fibers join the apertures on the internalsurface of the integument.The olfactory pores on the base of the tongue (fig. 5 B), maxillae(fig. 5 C), labial palpi (fig. 5 D),and the smallest on the mandibles, areof about the same size as those on the wings. The spindle-shapedsense cells are easily seen ; but owing to the small size of the pores, thepore apertures are rarely discernible. Beneath the group of poreson the labial palpus, the sense cells (fig. 5 D, SC) occupy about a halfof the space in the appendage. Fig. 5 E and F represent, respectively,the sizes of the pores found on the side of the head near the base ofthe mandible, and just inside the buccal cavity. A nerve (N2 ) anda trachea (fig. 2 F, Tr) run near the group of sense cells through thelabial palpus. Figure 2 I shows the structure of the largest olfactorypores on the cervical plate. These are equally as large as the largestones on the mandibles, but the smallest ones are never so small as thesmallest on the mandibles.Under the microscope with transmitted light the olfactory poresappear as bright spots. Each bright spot is surrounded by a darkline, the pore wall (fig. 5 G, PorW). Outside this line the chitin isgenerally dark in color, while inside of it the chitin is almost trans-parent, and at the center there is an opening, the pore aperture(PorAp).Figure 5 G to K represent, respectively, the sizes of the superficialappearances of the pores on the mandible, tongue, maxilla, labialpalpus, and cervical plate.To learn how well the mandibles are provided with sense organs,the reader is referred to figure 6 A. This is a semidiagrammaticdrawing taken from one cross-section through the middle of a man-dible of a 20-day-old worker pupa. The details of the hypodermis
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOO 31{Hyp) were taken from another section in which the hypodermal cellswere better fixed. Any section through the middle of a mandibleinvariably shows from two to four large pores, from one to threesmall pores, and one or more innervated hairs. The nearer the distalend of the mandible a section is taken, the fewer the large pores and
Fig. 6.—Internal anatomy of mandible of a worker honey bee, showing howwell this appendage is innervated. A, semidiagram of cross-section throughmiddle of mandible, showing innervation of olfactory pores (Por) and tactilehairs (ci), blood sinuses (BISin), nerve (N), nerve branches (NB), tracheae(Tr), etc. The details of the hypodermis (Hyp) were taken from anothersection, x 185. B, diagram of transverse-longitudinal view of mandible,showing innervation of olfactory pores (Por) and tactile hairs (bi, bi and c-,),and superficial appearances of these sense organs. The hairs in solid black arenot innervated, while all the others are connected with sense cells (SC). Seepage 54 for other abbreviations.the greater the number of small pores and innervated hairs it shows.Large hypodermal cells, called hair-mother cells (HrMC), are oftenseen beneath the largest hairs on the mandibles. They send processes
32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65into the hairs through which the cellular secretion passes to formthe hairs. At first sight these cells resemble sense cells, but a furtherstudy shows that they are quite different. The tracheae (Tr) aresuspended to the hypodermis by connective tissue (ConT) and thenerves (N) are suspended to the tracheae in the same manner. Allthe space not occupied by the enumerated structures may be calledblood sinuses (BISin).A still better idea of how well the mandibles are innervated isgained by referring to figure 6 B. This is a transverse-longitudinaldiagram showing the main nerve (N) sending off branches to thesense cells (SC) belonging to the olfactory pores (Por) and the threevarieties of innervated hairs (blt b± and c7 ).
3. Disposition of the Innervated HairsIn the preceding pages the distribution and number of the senseorgans on the mouth-parts have been briefly discussed in connectionwith their anatomy. Now since we have classified these organs onthe basis of their structure, their disposition will be given in detail.In counting the number of sense organs herein discussed, five individ-uals each of workers, queens and drones have been used. Owing tosome of the parts being mutilated and concealed, a few of the groupsof hairs and olfactory pores could not be counted ; so it was necessaryto estimate the number in such groups. It was not possible to countall the sense organs on the mandibles on account of the opaquenessand rotundity of these appendages ; therefore, only estimates of allthe sense organs on the mandibles except variety b x of the hairs willbe given. (a) spinelike hairsVariety a. This variety is found only on the epipharynx. Theepipharynx is a large three-lobed appendage (fig. 9 A, Ep) dependingfrom the roof of the preoral cavity (fig. 10, Ep) just in front of themouth (Mo). It is movable up and down and serves to close themouth opening. These hairs (fig. 9 A, a) are arranged in two groupsat the base of the epipharynx, a group lying on either side of the high,vertical, keel-shaped median lobe (K) of the so-called dorsal tongue.For workers, the number of hairs in a single group varies from 41to 79 ; in a pair of groups, from 83 to 147, with an average of 104 hairsfor one worker. For queens, the number of hairs in a single groupvaries from 24 to 92 ; in a pair of groups, from 55 to 176, with anaverage of 103 hairs for one queen. For drones, the number of hairs
NO. 14 SENSE OBGANS ON MOUTH-PARTS OF BEE—McINDOO 33in a single group varies from 40 to 74 ; in a pair of groups, from 82 to134, with an average of 101 hairs for one drone. It is thus seen thateach caste possesses virtually the same number of hairs on theepipharynx.Variety b. Hairs marked b 1 are found only at the proximal end ofthe mandible on the outer, dorsal corner (fig. 7, b t ) . There are about85 in each group.Hairs marked b 2 occur only on the inner surface of the mandible, onan elevated ridge (figs. 8 and 10, Rg) just posterior to the biting sur-face (BS) . Each mandible has a single row of these organs, consist-ing of about five hairs.Hairs marked b 3 are present only on the pharyngeal plate. Thisplate is a strong chitinous structure forming the anterior part of thefloor of the pharynx (fig. 10, PhPl) . It has two terminal points ( figs.9 B and 10, TP) hanging downward over the lower rim of the mouthand two long chitinous rods which are attached to the sides of theplate. These rods (PhPIR) run around the sides and to the top of thepharynx (Ph) , where they are fastened to muscles which in turn areattached to the chitin on the top of the head. The posterior part of thepharyngeal plate is arched upward, forming two large domes, witha deep groove between the domes. The hairs under discussion aregrouped on these domes. Some of the hairs point forward, somebackward and others toward the roof of the pharynx. The numberof hairs in the groups varies only slightly. As an average for workers,there are 90 hairs on a pharyngeal plate ; for queens, 74 hairs ; and fordrones, 66 hairs. It is thus seen that these hairs in the three castesvary considerably in number.Hairs marked &4 (fig. 7) are found only on the outer surfaces ofthe mandibles at the tips. They are arranged irregularly, except thatone row follows the contour of the biting edge. The hairs in this rowproject slightly beyond this edge and often curve over it. Thereare probably 100 of these hairs on each mandible.Variety c. Hairs marked c x are present on the flagella of theantennae where there are no pore plates. Those marked c2 are usuallyfound between the pore plates. Those marked c 3 occur only on thescapes of antennae.Only a few hairs marked ci (figs. 7 and 8) occur on each maxilla.Twenty-five marked c5 are found on the base of each maxillary palpus.Only a few marked c6 are present among the olfactory pores on theinner surface of the labial palpus. About 75 marked c- occur on eachmandible, the most of them being on the outer surface, and about 40
34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
of the same kind are found at the base of each paraglossa on thedorsal side. About 35 hairs are present on each cervical plate, themost of them being the ones marked c10 . This plate is a heavy chitin-ous structure on the " throat " of the bee (figs. 9 C and 10, CvPl),and the writer has called it the " cervical " plate on account of its
Fig. 7.—-Diagram of mouth-parts of a worker honey bee spread out fiat,showing disposition of innervated hairs (61, b*, U to cT, Cu to Cis, ex and /) andolfactory pores (Por), on dorsal surfaces of glossa (Gls), paraglossa (Pgl),palpigers (Pig), mentum (MO, and labrum (Lm), on inner surfaces of labialpalpi (LbPlp), and on outer surfaces of maxillae (Mx) and mandibles (Md),x 25. All the hairs shown are innervated, and the pseudo-hairs on the glossahave been omitted. See page 54 for other abbreviations.position. It has two deep folds, in the anterior one (fig. 9 C and10, F) of which may be seen the tactile hairs (cs to c10 ) and olfactory-pores (Por). A few scattered, innervated hairs were found justinside the buccal cavity, a few on the side of the head and a few on
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 35
Q
COHs
"5,(2
36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65top of the head (fig. 10, c13 ). Several were seen on each palpiger(figs. 7 and 8, c 14 ) and several, marked c13 , on the ventral surface andsides of the mentum. Eighty-three hairs marked c16 were counted onthe tongue. The most of these lie on the ventral side. Several inner-vated hairs marked c17 were seen on each side of the labrum near theanterior edge. All the large hairs marked c18 on the maxillse andlabial palpi seem to be innervated.(b) PEGLIKE HAIRSVariety d. Those marked d± and d2 are found only on the flagellaof the antennae.Variety e. Those marked ex are found on both sides of the maxillsenear the maxillary palpi. There are perhaps 50 on each maxilla.Only a few marked e 2 are present on the base of each labial palpus.Variety f. Several marked / occur at the distal end of each max-illa and labial palpus.In conclusion under this heading it is seen that all the true hairson the tongue are innervated, while practically all on the maxillse,labial palpi, palpigers, paraglossse and mentum are connected withnerves. All of those near the anterior edge of the labrum and all onthe mandibles, except two varieties of large hairs (figs. 6 B, Hr1 and10, Hr2 ), are also connected with sense cells.Table VIII is a tabulated summary of the disposition of theinnervated hairs herein discussed. The blank spaces mean that hairswere not looked for on the appendages recorded.
4. Disposition of the Olfactory PoresOlfactory pores (figs. 7 and 8, Por) were found irregularly dis-tributed over the entire surface of the mandibles (Md), except on thebiting surfaces (BS) and between the two ridges (Rg) . Very fewoccur on the proximal half of this appendage, while they are quiteabundant on the distal half. There are at least 150 on each mandibleof the workers.On the tongue (fig. 7, Gls) olfactory pores were found only on thedorsal side at the base. These are arranged in two groups, eachgroup being located on a prominence just posterior to the notch (Nt)
.
A groove (Gv2 ) connecting with the two notches runs between thetwo prominences and continues as a shallow depression (Gv3 ) to thebase of the mentum (Mt). The number of pores in either group onany given tongue is almost constant, and the individual variations
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 37
pIG 8 —Diagram of mouth-parts of a worker honey bee spread out flat, show-ing disposition of innervated hairs (6 2 , u, cM to cw , ex, eh and /) and olfactorypores (Por) on ventral surfaces of glossa (Gls), palpigers (.Pig), mentum(Mt) and labrum (Lm), on outer surfaces of labial palpi (LbPlp), and oninner surfaces of maxillae (M^r) and mandibles (Md), x 25. The mandiblesand labrum are seen by looking through the other appendages. All the hairsshown are innervated, and the pseudo-hairs on the glossa have been omitted.See page 54 for other abbreviations.
38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
are insignificant, but the caste variations are sufficiently large toindicate that queens and drones do not have as strong likes anddislikes for foods as do workers. As an average for workers, thereare 48 pores on each tongue ; for queens, 32 pores ; and for drones,31 pores.On the inner surface of each labial palpus (fig. 7, LbPlp) a groupof olfactory pores (Por)* extends entirely across the base of thisappendage. These groups are always present and the individualvariations are slight. As an average for workers, there are 34 poreson each labial palpus ; for queens, 24 pores ; and for drones, 23 pores.On the inner surface of each maxilla (fig. 8, Mx) near the max-illary palpus (MxPlp) there is a group of olfactory pores (Por).This group is never absent and the individual variations in numberof pores in it are slight. As an average for workers, there are 28pores on each maxilla ; for queens, 20 pores ; and for drones, 20 pores.A group of olfactory pores (figs. 9 C and 10, Por) is alwayspresent on the cervical plate (CvPl). As an average for workers, thisgroup contains 26 pores ; for queens, 24 pores ; and for drones, 23pores.A few olfactory pores were seen in each of the following places
:
just inside the buccal cavity, on each side of the head, and on the baseof the scape of each antenna.Table IX is a tabulated summary of the disposition of the olfac-tory pores herein discussed and those previously found elsewhereon the honey bee by the writer. The plus sign, " +," means thatthere were more than the number recorded. The single questionmark, " ?," means that the pores were estimated ; and the double ques-tion mark, " ? ?," means that the numbers recorded were computed byusing the ratios of the total number of pores on the other mouth-partsas a basis.It is thus seen that drones as an average have a few more than2,948 olfactory pores ; workers a few more than 2,766, and queens afew more than 2214 olfactory pores.In various papers the writer has shown experimentally that theolfactory pores on the legs and wings of hymenopterous and coleop-terous insects receive odor stimuli, and it is only reasonable to sup-pose that the same organs on the mouth-parts perform the same or asimilar function, although we have no way of knowing whetherthe sensation produced is that of smell or that of taste. Judgingfrom the anatomy of the organs, we are inclined to call the sensationsmell, but judging merely from the experiments to determine whether
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 39bees have likes and dislikes in regard to foods, the indications are thatbees have a sense more or less similar to our sense of taste.To ascertain whether the elimination of the olfactory pores on thewings would produce any effect upon the ability of bees to discrim-inate between foods, the wings of 20 workers were pulled off at theirarticulations. Such an operation eliminates all the sense organs on thewings, and the writer has previously shown that bees without wingsbehave normally in all respects except that they respond more slowlyto odor stimuli. These 20 bees were fed pure cane-sugar candy andcane-sugar candy containing- strychnine, as described on page 14. Atfirst a few ate a little of the poisoned candy, but after that not a singlebee was seen eating it, but they ate the pure cane-sugar candy nor-mally. This indicates that when the 1500 pores on the wings areprevented from functioning, the remaining 1200 pores found else-where on a worker are sufficient to enable the bee to distinguish thecandy containing strychnine from the pure candy. These experi-ments showed that further experimentation along this line wasuseless.
5. The Tactile Sense of the Honey BeeSince the innervated hairs herein discussed certainly cannot serveeither as olfactory or as gustatory organs, there still remain only twoknown senses which we might consider in connection with thesehairs. (1) An auditory function has never been attributed to anyof these hairs, but similar hairs on spiders have been called auditoryhairs. We need not consider the sense of hearing further. (2) Thetactile sense seems to be the most plausible function to attribute tothem, although no experiments were performed to test this view.If we call these innervated hairs tactile hairs, we can easily explainmany of the activities of bees. Since bees are covered with a hardchitinous integument, a person often wonders how it is possible thatthey can perform their many duties of caring for the brood, buildingcomb, etc., unless they have an acute sense of touch. They certainlycannot feel weak mechanical stimuli through the integument as wedo through the skin, and for this reason various kinds of hairs havebecome innervated.Instead of the innervated hairs on the tongue being gustatory infunction, they are certainly used chiefly in examining food as towhether it is solid or liquid. If the food should be solid and mustbe dissolved before being eaten, these hairs perceive stimuli whichcause a copious flow of saliva. If the food should be a solid and
40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 6s
not to be dissolved, it is first probably examined by the maxillae andlabial palpi before being seized by the mandibles. Ey means of themany sense hairs covering the mandibles, these appendages are ableat any moment to perceive the size, shape and firmness of the food
;
and when the food particles are sufficiently small to be swallowed,they are placed upon the dorsal side of the mentum (fig. 7, Mt).While watching a bee eat, it is easily observed by using a pair ofbinoculars that the mentum (fig. 10, Mt) may be moved in threedirections. The forward and backward movement is most noticeable.The second movement is up and down and the third is a sidewise
A
Fig. 9.—Superficial appearances of the innervated hairs (a, d~, bz, cs to C10)on the epipharynx, labrum, pharyngeal plate and cervical plate, and of theolfactory pores (Por) on the cervical plate of worker honey bees. A, ventralsurfaces of labrum (Lra) and epipharynx (Ep), showing two groups ofvariety a of innervated hairs on prominences at base of epipharynx, x 45. B,inner surface of pharyngeal plate, spread out flat, showing two groups ofvariety b of innervated hairs (b s ) on dome-shaped prominences at posteriorend of this plate, x 45. C, outer surface of cervical plate (CvPl), spread outflat, showing a group of variety c of innervated hairs (c8 to cio) on either sideof this plate with a long group of olfactory pores (Por) between them, x 50.For other abbreviations see page 54.
one. The mentum, including the appendages attached to it, acts likea small crane which may be moved backward and forward, up anddown, and from side to side to a limited degree. The mentum ismoved forward when the food particles are to be conveyed from themandibles to the mouth. After these particles have been placedupon the mentum posterior to the paraglossae, the mentum is movedbackward and upward through the buccal cavity (BCav) until theparticles are at the mouth opening (Mo). The tactile hairs inside
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 4I
this cavity may be stimulated by the particles touching them, therebyinforming the bee that the food is ready to be swallowed. Thepresence of the food in the mouth is made known to the bee by meansof the hairs on the epipharynx (Ep) coming in contact with it. Theact of swallowing is facilitated by means of the epipharynx pushingthe food into the mouth. This act is explained by the fact that thefleshy-like epipharynx may be moved up and down by a set of longi-tudinal muscles (M3 ), and it is also capable of completely closing themouth opening by the longitudinal (M3 ) and transverse muscles(M10 ) working in unison.Should a particle of food, too large to pass through the narrowoesophagus (fig. 10, E), be swallowed, it would be stopped when itreached the hairs (&3 ) on the pharnygeal plate (PhPl) by means ofthe transverse muscles (M10 ) contracting, thereby forcing it to theexterior. It is thus seen that the hairs on the pharyngeal plate act asa safety device to prevent pieces of solid food, too large to go throughthe oesophagus, from passing into the pharynx (Ph).The tactile hairs on the maxillae and labial palpi are of the utmostimportance to workers while caring for the brood and in examiningthe comb, etc. The hairs marked &.t on the mandibles perhaps playtheir greatest role while these appendages are being used for buildingcomb. Regarding these as tactile hairs, it is easy to understood howbees are able to mold the walls of all the cells of uniform thickness.
6. How Bees Eat Liquid FoodsWhile watching a bee eat honey under a simple microscope, it willbe observed that the maxillae remain almost stationary while thementum, carrying the tongue, paraglossia and labial palpi, is beingmoved forward and backward, up and down through the buccal cavitybetween the maxillary bases as if the honey were being either pumpedor sucked up into the mouth. It is now generally believed thatliquid foods pass up the glossa or tongue by capillary attraction andare then sucked into the mouth. This view seems to be the onlyplausible one, and after completely understanding this method it isseen that Nature could not have devised a better plan. If a bee ateonly liquid foods, a proboscis connecting directly with the mouthwould be a better apparatus, but we well know that bees eat more orless of solid food in the form of pollen.As a typical example to serve all purposes, let us suppose that abee is about to eat candy containing a small amount of quinine, andlet us suppose that the bee cannot smell the quinine in the candy.4
42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65The bee probably first recognizes the candy as food by smelling itbefore touching it. After smelling the candy the first reaction of thebee is to move toward it, to extend the tongue and to examine thefood with the sense hairs on the tip of the tongue. The extending ofthe mentum (fig. 10, Mt) is accomplished by muscles not shown infigure 10. The tongue is unfolded from beneath the mentum bythe contraction of a pair of muscles (M2 ), attached to a pair of hardchitinous processes (Pr). The tongue is folded beneath the men-tum by means of two muscles (fig. 10, M x ) pulling on a pair of chi-tinous rods (-^1) which are the two forks of the chitinous rod (R)extending the full length of the glossa through the center. When thetongue is extended and as quickly as the bee recognizes that the foodmust be dissolved, the salivary syringe (SS) forces its supply of salivato the exterior, at the point marked 6" in figures 7 and 10. The salivaruns forward along the groove between the two groups of olfactorypores (fig. 7, Por) and passes around the notches (Nt) to the ventralside of the tongue, where it enters the proximal end of the groove (fig.8, Gv) which extends the full length of the glossa. The extreme prox-imal end of the groove is wide and shallow, and at this place there is nodistinction between the gfroove (fig. 3 A, Gv) proper and the canal(Can) formed by the rod (R) . Not far from the notches the widegroove becomes narrow and deep and the canal is distinctly separatedfrom the groove. A portion of the ventral surface of the mentumextends as a fleshy tongue (fig. 8, Tn) along the roof and throughthe center of the wide groove. The end of this tongue terminateswhere the canal is separated from the groove. Now the saliva, intraveling from the external opening of the salivary syringe on thedorsal side of the tongue to the ventral side of the tongue by capillaryattraction, is guided into the canal by means of the fleshy tongue justdescribed. From this place to the tip of the tongue the canal is com-pletely separated from the groove by minute interlocking pseudo-hairs(fig. 3 A, Hr 3 ) which point toward the tip of the tongue. Accordingto the law of capillarity the saliva, aided by the pseudo-hairs, passesthrough the canal as rapidly as oil climbs a wick. The saliva, afterreaching the tip of the tongue, spreads over the surface of the spoon-shaped labellum (fig. 8, Lbl) which is used for scraping the candy.The scraping and changing of the sugar to liquid is facilitated by themany forked pseudo-hairs on the labellum. When the food is dis-solved, it enters the grqove at the tip of the tongue, passes throughthe entire length of the groove to the base of the tongue, where itthen passes through the notches to the dorsal side of the tongue and
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—MdNDOO 43then along the groove (fig. 7, Gvt ) to the place marked X on thedorsal surface of the mentum (fig. 10).While eating honey and syrup greedily, the distal half of the groovemay be opened widely to the exterior so that the liquid may enter morerapidly. Since there are no muscles in the glossa, the only way to ex-plain the opening of the groove is by supposing that the blood rushes
Ftp to—Diagram of sagittal section through head of a worker honey bee,sliStly lateraUo Median line of head, pharyngeal plate P^/)epiPharynx(Ep) labrSm (L»), cervical plate (CvPl), mentum (M ), Pa^°fsa (FjO,E5W?^ea^a^^S mSles (Ma to Mu ) attached to epipharynx, pharyngeal plate and walls ofphaTynx! Muscles marked M, and M2 fold and unfold glossa respectively. Forother abbreviations see page 54.into this part of the tongue and the edges of the groove (fig. 3 A, Ed)are widely separated by blood-pressure. In sections the rod (R) isoften everted to the outside of the tongue.
44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65According to the law of capillarity the height to which a liquid rises,in a tube varies inversely with the diameter of the tube. In otherwords, the smaller the tube the higher a liquid rises in it. Using atube four times as long as the glossa and with the diameter equal tothat of the average diameter of the groove in the glossa, water wouldrise to the top of the tube merely by capillary attraction. This demon-strates that licfuids quickly pass through the groove, and the move-ment of them is increased by the aid of the many pseudo-hairs (fig.3 A, Hr2 ) lining the groove and by some of them interlocking at theextreme edges of the groove to exclude the outside air. These hairspoint toward the base of the tongue, making the groove as capable ofcarrying liquids as a wick is of lifting oil from the bottom of a tallbottle.At the proximal end of the groove the liquid is turned to eitherside of the glossa by the fleshy tongue (fig. 8, Tri), and is preventedfrom traveling further on the ventral side of the mentum by theshoulder which is formed by the two chitinous processes (Pr) pro-jecting below the ventral surface of the glossa. The shallow groove(fig. 7, Gz\) on top of the tongue probably serves to hold the excessof liquid when it has difficulty in following its proper course.As soon as saliva mixes with the food, a chemical or physicalchange is effected, and this change perhaps liberates odors that werenot smelled by the bee before the food was eaten. Again, the salivamight so affect the quinine in the food described on page 14 that thefaintest odor imaginable could be detected by the pores on the baseof the tongue, and also probably by those on the labial palpi andmaxillae. It must be remembered that while the liquids are passingfrom the ventral side to the dorsal side of the tongue, and vice versa,the paraglossae close around the tongue, making a perfect tube, andthe labial palpi close tightly against the paraglossae, and the maxillarylobes are folded around all of these appendages. It is thus seen thatthe olfactory pores on the glossa, labial palpi and maxillae are almostagainst the liquid as it passes to the base of the mentum, for, asalready pointed out, the pores on the labial palpi and maxillae lie onthe inner surfaces of these appendages.This closes the description of the role played by capillary attractionin carrying liquids from the tip of the tongue to the base of thementum. The entire process is clear to the writer except where thesaliva and liquid food pass around the base of the tongue. It isstrange that both liquids can travel in opposite directions along thesame route by no force other than capillarity. This is partially
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 45
elucidated by the fact that the paraglossae, in closing- tightly aroundthe base of the tongue, make a perfect tube which connects the grooveon the ventral side of the glossa with the one on the dorsal side of thesame appendage, and perhaps most of the liquid food is sucked into themouth from the cavity formed by the paraglossce.We are now ready to explain how the liquid is sucked into the mouth.Cross-sections through the head of the bee show that the pharynx(fig. 10, Ph) assumes various shapes, but the shape shown in figure10 is the most typical. Just posterior to the hairs (63 ) on the pharyn-geal plate, it expands into a large, saclike body, while its posterior endgradually becomes smaller and is called the oesophagus (£) where itenters the thorax. The walls of the alimentary tract, from the mouthto the honey stomach, were examined to see if they contain senseorgans, but none was found other than those already described.Nerves running to the cervical plate (iV6 ), pharyngeal plate (A^) andthe epipharynx (A/"4 ) were seen, but no other nerves were observedconnected with the pharynx, although several muscles were tracedfrom the pharynx to their places of attachment. A study of thesemuscles shows that the pharynx may be moved in at least six differentways as follows: Muscles marked M4 pull it forward; M5 , upward;M6 andM7 , upward and backward ; M8 , directly backward ; MQ , down-ward and backward ; and M10 and In change the diameter of it.It will be seen that M7 is attached to the pharyngeal plate rod(PhPIR) and M8 is fastened to the pharyngeal plate. The contrac-tion of either one of these muscles would enlarge the tube leadingfrom the mouth to the pharynx. From the preceding descriptionit is easily understood that by various combinations of these musclesthe pharynx works like a powerful pump, and when the liquid foodon the dorsal surface of the mentum is raised to the mouth opening,the suction from the pharynx draws it into the mouth as easily asa person draws into his mouth water held in the palm of the hand.
7. Summary of Sense OrgansOnly two general types of sense organs were found on the mouth-parts of the honey bee. They are innervated hairs and innervatedpores, called olfactory pores by the writer (1914a). Judging fromtheir anatomy, the innervated hairs can serve only as tactile organs,and none of them are anatomically adapted to function either asolfactory organs or as gustatory organs. The writer has divided theminto spinelike and peglike hairs. Both types vary considerably insize and structure. In size the spinelike hairs vary from the smallest
46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
ones on the antennae to the largest ones on the maxillae and labialpalpi ; the peglike hairs, from the short and thick ones on the maxillaeto the saber-shaped ones on the labial palpi and maxillae. The spine-like hairs were found on all the mouth-parts, pharyngeal plate, an-tennae, in the buccal cavity, all over the head and on the cervical plate.The peglike hairs were observed only on the antennae, maxillae andlabial palpi.Judging from the disposition and innervation of the hairs underdiscussion, the tactile sense in the honey bee is highly developed. Theapplication of this perception easily explains how bees are able toperform their many duties, such as caring for the brood, buildingcomb, etc.The act of eating liquid foods is accomplished by capillary attrac-tion, and by the pumping force of the pharynx.Olfactory pores were found at the bases of the tongue and labialpalpi, on the maxillae near the maxillary palpi, widely distributed overthe mandibles, on the cervical plate, in the buccal cavity, on the sidesof the head and on the scapes of the antennae. Their structure isidentical with that of the olfactory pores on the legs, wings and sting,and therefore their function should be the same.DISCUSSION OF LITERATUREA review of the literature pertaining to the sense organs on themouth-parts and to the gustatory sense of insects shows so much con-fusion in regard to the names of the various sense organs and theirprobable functions that it is impossible to classify the various struc-tures correctly. The present writer has separated all the sense organson the mouth-parts of the honey bee into olfactory pores and inner-vated or tactile hairs, the latter group being divided into spinelike andpeglike hairs. Other writers have called the hairs setae, pegs, cones,bristles, or just " hairs," and the few who have seen the olfactorypores have called them taste-pits, taste-cups, taste-papillae or beaker-shaped organs, etc. Let us consider the olfactory pores first.Meinert (1861) seems to be the first to suggest that insects havegustatory organs. He described a row of chitinous canals on themaxillae and base of the tongue of ants. He thought they were inner-vated and might serve as gustatory organs. Forel (1873) saw thesame or similar structures on the maxillae and tongue of Formica,and he called them gustatory papillae.Wolff (1875) first described the olfactory pores on the base of thetongue of the honey bee. He called them taste-beakers in analogy
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE McINDOO 47
to the gustatory organs at the base of our tongues, and he thoughtthat the secretion of the salivary glands, always present inside theglossal covering, kept the beakers constantly moist and gustatorystimuli were effected by the saliva changing the honey which passesthrough the groove in the glossa.Joseph (1877) saw taste-pits on the bases of the tongues of speci-mens belonging to nearly all the insect orders, and especially on thoseof plant-eating insects.Kraepelin (1883) thought that he found gustatory organs on theproboscides of flies. These were seen on the inner surface of thecushion of the labellum. From his description they may be the sameas the olfactory pores under discussion.Will (1885) described the olfactory pores on the tongue, maxilkeand labial palpi of the honey bee and various other insects in muchthe same manner as depicted by the present writer. He called thembeaker-shaped organs and imagined that they receive gustatorystimuli because the peripheral ends of their nerves come in directcontact with the food. He saw two groups of them on the base ofeach tongue, and the number of organs in each group varies asfollows : Apis (worker) , about 25 ; Osmia, 14 to 16 ; Bombus, 20 to 24
;
and Ichneumonidse, 12 to 14. About 40 organs were seen in eachgroup on the maxilla? of the Apidae, but very few in the Tenthredin-idae. Will failed to understand the internal anatomy of these organs.He thought the sense cells are multinucleated and that their sensefibers pierce the thin membranes covering the beakers in order tocome in contact with the external air.Breithaupt (1886) describes the pits or pores found on the baseof the tongue of the honey bee. Being unable to make thin sectionsthrough these organs, he constructed a schematic drawing of a singlepore which shows the sense fiber of the spindle-shaped sense cell run-ning to the extremely thin and transparent membrane which coversthe pore.Vom Rath (1886) seems to have found organs similar to the olfac-tory pores in the labium of millipedes (Chilognatha) . Each organ isporelike and is two-thirds filled with a pear-shaped bundle of nervefibrillar which pass through the fine pore aperture and come in con-tact with the external air. The same author (1887, 1888) seems tohave seen the same organs on the palpi of beetles.Janet (1904) found a constant group of olfactory pores on eachlabial palpus, two rows on the tongue, and some on the pharynx ofants. Those seen by him on the pharynx perhaps really lie on the
48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
cervical plate, as already described by the present writer, becauseeither in sections or in whole mounts of the integuments of the headsit is often difficult to determine whether the pores lie on the pharyn-geal plate or on the cervical plate. Janet (1911) saw the sameorgans widely distributed over the integument of the mandibles of thehoney bee. According to him, all the pores, whether on the mouth-parts or on the legs, have a similar structure, and they resemble thestructure of the olfactory pores described by the present writer ; how-ever, there are a few slight differences. He calls the chitinous cone anumbel, which is always separated from the surrounding chitin by achamber. This chamber communicates with the exterior by means ofthe pore. The sense fiber, or his manubrium, runs into the umbel,and he thinks that it spreads out over the inner surface of the umbeland does not open into the chamber. Thus the umbel forms a thinlayer of chitin which separates the end of the sense fiber from theexternal air. Janet thinks that the role of these organs is evidentlyto permit the end of the nerve to become distributed on a surfacerelatively large and separated from the air only by a thin layer ofpermeable chitin. He imagines that they are special olfactory organs,but different from the olfactory organs on the antennse. In regard tothose on the mandibles, he believes that they aid in building comb andin collecting pollen and propolis.Hochreuther (1912) found a few olfactory pores on the epicraniumnear the margin of the eyes, 11 on the first and second joints of theantennas, a few on the dorsal side of the labrum, very few on thedorsal side of the mandibles, several on the maxillae and many on thelegs of Dytiscus marginalis. He called them dome-shaped organsand describes and gives drawings of them in a manner somewhatsimilar to that of Janet.We shall now discuss the innervated hairs only briefly, because, asalready pointed out, they probably serve neither as olfactory organsnor as gustatory organs.Wolff (1875) was the first to describe the hairs on the epipharynx.In the honey bee he described each organ as a small cone with a pitin the summit bearing a small hair. He thought that each hair is con-nected with a sense cell group and that these organs receive olfactorystimuli.Kunkel and Gazagnaire (1881) found innervated hairs on theparaglossse, on the epipharynx and on the pharyngeal plate of Diptera.They imagined that these hairs receive gustatory stimuli.
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 49Becker (1882) found sense hairs on the ventral side of the labrumof certain Diptera. He believed that they serve as gustatory organs.Haller (1882) says that the small hairs and pegs on the dorsal sideof the labium of Hydrodroma rubra probably serve as gustatoryorgans.Kraepelin ( 1882, 1883) attributes a gustatory or olfactory functionto certain innervated hairs on the proboscides of Hymenoptera andDiptera.Kirbach (1883) calls certain small hairs in Lepidoptera gustatorypapillae.Briant (1884) regards the innervated hairs on the tongue of the beeas merely tactile organs and not as gustatory structures as generallybelieved.Sommer (1885) found innervated hairs on the legs, palpi, labrumand labium of Macrotoma plumbea (Thysanura), but he saysnothing about their function.Will (1885) gives a drawing of a hair from the tip of the tongueof Vespa, but none from Apis nor Bombus. The sense cell is multi-nucleated, and the sense fiber stops in the base of the hair, whose wallsare thick.Breithaupt (1886) described papillae with very short hairs on themouth-parts of Bombus. He thinks that some serve as gustatoryorgans while others serve as tactile organs, the function being deter-mined by the location of the hairs.Gazagnaire (1886) says that the gustatory organs in Coleopterashould be found in the buccal cavity in the form of hairs.Vom Rath (1887, 1888, 1894, 1896) has made a comprehensivestudy of the morphology of all kinds of hairs on the mouth-partsbelonging to various insect orders. All his drawings are good, andeach sense hair, peg or cone is usually innervated with a sense cellgroup, but sometimes with a single sense cell.Reuter (1888) describes cone-shaped sense hairs on the palpi ofLepidoptera. These are connected with sense cell groups.Packard (1889, 1903) studied the epipharynx in various insectorders. He almost invariably found hairlike sense organs on eachepipharynx examined. These organs are setae associated with sensepits, cups and rods. Packard seems to think that some of the setaeare used merely to guard the sense cups while the others aid the sensecups in receiving gustatory stimuli.Nagel (1892, 1894, 1897) has made a special study of the mor-phology of the olfactory and gustatory organs of insects. He divides
50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
the organs receiving gustatory stimuli into inner gustatory organsand outer ones. The inner ones found inside the buccal cavity arelocated on the epipharynx as minute pit-pegs or cones. The outerones are found outside the buccal cavity on the various mouth-parts.They are cones and pit-pegs of various sizes and shapes.Rohler (1906) found various kinds of sense hairs on the mouth-parts of the grasshopper, Tryxalis. He thinks that some of theseserve mechanically to examine the food, while the others function asgustatory organs.The following is a brief discussion of the experimental work per-taining to the sense of taste.Forel (1873, 1908) was apparently the first to determine experi-mentally that insects show preferences between foods. When mor-phine and strychnine are mixed with honey, he says that ants do notat first recognize these substances by smell, but after eating a littlehoney containing these substances, they immediately leave it. Antsdo not always know how to distinguish foods containing injurioussubstances, because when he fed them honey containing phosphorus,they gorged themselves with it and many of them soon died. Inrepeating the experiments of Plateau (1885) and Will (1885), Forelamputated the antennae and the four palpi of several wasps. Whenhe fed them honey containing quinine, they soon left it after eating alittle of it, but greedily ate pure honey not containing quinine. Fromthis he concludes that the gustatory faculty is independent of theantennae and palpi, and that it resides in the mouth. He agrees withPlateau and Will that the amputation of the palpi in no way modifiesthe olfactory, gustatory or masticatory faculties. He thinks thatthe palpi serve as special tactile organs.Will (1885) carried on a series of experiments to demonstrate thesense of taste in insects. He ascertained that wasps, bees, and bumble-bees soon leave foods containing alum, quinine, and salt after eatinga little of them. He thinks that the gustatory perception lasts a ratherlong time, because insects, after eating foods containing these sub-stances, clean their mouths for several minutes and then, when givenpure honey, " taste " it several times before definitely beginning toeat. As a general rule, Will found that the larvae are more " diffi-cult to please " in the choice of their foods than the imago insects.Lubbock (1899) noticed that some individual ants seem to possessa finer sense of taste than others, and he thinks this is partially ex-plained by the fact that the number of taste-pits is not the same in allindividuals. He concludes " that the organs of taste in insects are
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McINDOO 5
1
certain modified hairs situated either in the mouth itself or on theorgans immediately surrounding it." " But though the loweranimals undoubtedly possess the sense of taste, it does not, of course,follow that substances taste to them as they do to us. I have foundby experiment that sugar and saccharine, which are so similar to us,taste very differently to ants and bees."In conclusion under this heading, the results obtained by the pre-ceding authors are less satisfactory in explaining that insects havea true gustatory sense than the results obtained by the present authorin showing that insects do not have a true gustatory sense, becausethe preceding authors have found no organs anatomically adapted forreceiving gustatory stimuli. Even if the antennze are amputated, theolfactory organs are not eliminated, because olfactory pores arewidely distributed over the integument, and for this reason theolfactory sense cannot be eliminated while testing for the sense oftaste. The present writer's opinion is that insects do not have a senseof taste, because their highly developed olfactory organs are suffi-ciently capable of receiving the odors, however weak, from any andall substances. Whenever the odors are extremely weak, it is thennecessary for the insects to eat a little of the foods containing theundesirable substances before being able to smell these substances.For this reason the present writer has called this faculty an olfactory-gustatory sense, although according to the definition of the senseof taste in vertebrates the gustatory perception plays no part in theresponses. GENERAL DISCUSSIONThe present writer, and the few other authors who have fed insectsfoods containing undesirable substances, have observed that theinsects sooner or later refuse such foods after eating more or less ofthem. Judging from this behavior, the other authors have concludedthat insects can taste, regardless of knowing whether or not theyhave sense organs, anatomically adapted for receiving gustatorystimuli, and without considering the role played by the olfactory sensein these responses. As Parker has already said for vertebrates, andas we well know for ourselves, it is almost impossible to determinewhether we taste or smell certain substances when we eat them. Tous sometimes a food, before being eaten, emits only a faint odor or noodor at all ; but when we eat it, we perceive a pronounced odor. Insuch a case the odorous particles are not given off until the food istaken into the mouth and mixed with saliva. The same principle iscertainly applicable when bees eat candies which contain undesirable
52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65
substances emitting- extremely weak odors. As quickly as the salivahas dissolved the candy and has had time to effect a chemical orphysical change, the odorous particles are given off, and since theolfactory pores on the mouth-parts are nearest the food, they are thefirst ones to receive the odorous particles. For this reason the so-called gustatory sense in insects is only a phase of the olfactory sense.That we cannot smell certain substances is no proof that insectscannot smell them, for the many experiments performed by thepresent writer during the past four years cause him to believe that theolfactory sense in the honey bee is much more highly developed thanours.It is reasonable to think that many foods and chemicals emit odors,although we may not be able to perceive all of them ; but judging fromthe experiments herein discussed, it is not impossible for bees to dis-criminate between them better than we can. If they are not able to dothis without eating them, only a few " tastes " are necessary to demon-strate their preferences. In a few instances the present writer wasnot able to discriminate differences between candies containing certainchemicals by using both senses of smell and taste, but the bees wereable to distinguish marked differences. It therefore seems evidentthat this faculty in the honey bee is more highly developed than inman.In all probability bees have no other means of chemically discrim-inating between foods than by smelling them, because no sense organswere found connected with the alimentary tract between the pharyn-geal plate and the honey stomach, and because the innervated hairsdescribed are not anatomically adapted for this purpose. The wallsof the alimentary canal certainly cannot serve such a function exceptwhen corrosive or caustic substances are eaten.After once refusing foods which contain undesirable substancesemitting weak odors, bees seem to know these foods and seldomeat any more of them unless forced to partake of them by the removalof the foods they like better.In conclusion it may be said that the olfactory sense in the honeybee is highly developed and that it serves as an olfactory and gustatoryperception combined. LITERATURE CITEDBecker. 1882. Zur Kenntniss der Mundtheile der Dipteren. Denkschr. Acad.Wiss. Vvien, Bd. 45, p. 123.Breithaupt, P. F. 1886. Ueber die Anatomie und die Functionen derBienenzunge. Arch. f. Naturgesch., 52 Jahrg., Bd. 1, Heft 1, pp. 47-112,with 2 pis.
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—MdNDOO 53
Breithaupt, P. F. 1887. Anatomy and physiology of tongue of bee. Journ.Royal Micr. Soc, Part 1, pp. 224-225. Extract of above.Briant, T. J. 1884. On the anatomy and functions of the tongue of the honeybee (worker). Journ. Linn. Soc. Zool., London, vol. 17, pp. 408-416, with2 pis.Forel, Auguste. 1 873. Les fourmis de la Suisse. Ouvrage Soc. HelvetiqueSci. Nat., pp. 117-121.1908. The senses of insects. English translation by Yearsley, London,pp. 100-106.Gazagnaire, J. 1886. Recherches sur les organes de la gustation chez lesinsectes Coleopteres. Ann. Soc. Ent. France, (6), t. 6, bill., pp. 79-8o.Haller, G. 1882. Zur Kenntniss der Sinnesborsten der Hydrachniden.Arch. f. Naturgesch., 48 Jahrg., Bd. 1, pp. 32-46, with 1 pi.Hochreuther, Rudolf. 1912. Die Hautsinnesorgane von Dytiscus mar-ginalis L, ihr Bau und ihre Verbreitung am Korper. Zeitsch. f. wiss.Zool., Bd. 103, pp. 1-114.Janet, Charles. 1904. Observations sur les fourmis. Limoges, pp. 17-22.191 1. Organes sensitifs de la mandibule de l'abeille. L'Apiculteur,55 e Annee, No. 3, Mars, pp. 107-108.Joseph, G. 1877. Zur Morphologie des Geschmacksorgane bei den Insecten.Ber. 50 Vers. Deutscher Naturf. u. Aerzte, Miinchen, pp. 227-228.Kirbach, P. 1883. Ueber die Mundwerkzeuge der Schmetterlinge. Zool.Anz., 6 Jahrg., pp. 553-558.Kraepelin, K. 1882. Ueber die Mundwerkzeuge der saugenden Insecten.Zool. Anz., 5 Jahrg., pp. 574-579-1883. Zur Anatomie und Physiologie des Russels von Musca. Zeitsch.f. wiss. Zool., Bd. 39, pp. 683-719.Lubbock, Sir John. 1899. The senses, instincts and intelligence of animals.Intern. Sci. Series, vol. 65, London, p. 31.McIndoo, N. E. 191 1. The lyriform organs and tactile hairs of araneads.Proc. Phila. Acad. Nat. Sci., vol. 63, pp. 375-4*8, with 4 pis.1914a. The olfactory sense of the honey bee. Journ. Exp. Zool., vol.16, No. 3, April, pp. 265-346, with 24 text figs.1914b. The olfactory sense of Hymenoptera. Proc. Phila. Acad. Nat.Sci., vol. 66, pp. 294-341, with 3 text figs, and 2 pis.1915. The olfactory sense of Coleoptera. Biol. Bui., vol. 28, No. 6,June, pp. 407-460, with 3 text figs, and 2 pis.Parker, G. H. and Stabler, Eleanor M. 1913. On certain distinctions be-tween taste and smell. Amer. Journ. Phys., vol. 32, No. 4, PP- 230-240.Reuter, E. 1888. Ueber den "Basalfleck" auf den Palpen der Schmetter-linge. Zool. Anz., 11 Jahrg., pp. 500-503.Rohler, Ernst. 1906. Beitrage zur Kenntnis der Sinnesorgane der Insecten.Zool. Jahrb. Anat., Bd. 22, pp. 225-288, with 1 text fig. and 2 pis.Snodgrass, R. E., 1910. The anatomy of the honey bee. U. S. Dept. Agric,Bur. Ent, Tech. Ser. 18, Washington, Gov. Printing Office.Sommer, A. 1885. Ueber Macrotoma plumbea. Beitrage zur Anatomie derPod'uriden. Zeitsch. f. wiss. Zool., Bd. 41, pp. 683-718, with 2 pis.Vom Rath, O. 1886. Die Sinnesorgane der Antenne und der Unterlippeder Chilognathen. Arch. f. mikr. Anat., Bd. 27, pp. 4i9~437-
54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65Vom Rath, O. 1887. Ueber die Hautsinnesorgane der Insecten. Zcol. Anz.,10 Jahrg., pp. 627-631, 645-649.Ueber die Hautsinnesorgane der Insekten. Zeitsch. f. wiss.Zool., Bd. 46, pp. 413-454, with 2 pis.
—
- 1894. Ueber die Nervenendigung der Hautsinnesorgane der Ar-thropoden nach Behandlung mit der Methylenblau- u. Chromsilber-methode. Ber. naturf. Gesellsch., Freiburg, Bd. 9, pp. 137-164, with adouble pi.
— 1896. Zur Kenntnis der Hautsinnesorgane und des sensiblen Ner-vensystems der Arthropoden. Zeitsch. f. wiss. Zool., Bd. 61, pp. 499-539,with 2 pis.Will, F. 1885. Das Geschmacksorran der Insekten. Zeitsch. f. wiss. Zool.,Bd. 42, pp. 674-707, with 1 pi.Wolff, O. J. B. 1875. Das Riechorgan der Biene nebst einer Beschreibungdes Respirationswerkes der Hymenopteren, etc. Nova Acta Kls. Leop.-Carol. Deut. Akad. Naturf., vol. 38, pp. 1-25 1, with 8 pis.ABBREVIATIONS
a variety a of innervated hairsbi to ht variety b of innervated hairsCi to Cis variety c of innervated hairsdi and d2 variety d of innervated hairsei and e2 variety e of innervated hairsf variety / of innervated hairsBCav ' buccal cavityBISin blood sinusBS biting surface of mandibleCan canal in rod of glossaCh chitinChi ... flexible chitinCon cone of olfactory poreCom cone of innervated hair on epipharynxConT connective tissueCvPl cervical plateE esophagusEd edge of groove on glossaEp epipharynxF fold in cervical plateGls glossa, tongue or proboscisGv, Gvi to Gv3 . . . grooveHri and Hr2 non-innervated hairs on mandibleHrl to Hr3 pseudo-hairs on glossaHrCav hair cavityHrMC hair-mother cellHrSk hair socketHyp hypodermisHypNuc hypodermal nucleusHypS hypodermal secretion
NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE—McTNDOO 55K keel-shaped lobe of epipharynxL lumenLbl labellum of glossaLbPlp labial palpusLm labrumLr lorumMi to Mu musclesMd mandibleMo mouthMt mentumMx maxillaMxPlp maxillary palpusN, Ni to No nervesNB nerve branchNeu neurilemmaNF nerve fiberNkFl neck of flask-shaped poreNt notch at base of glossaPgl paraglossaPh pharynxPhPl pharyngeal platePhPIR pharyngeal plate rodPig palpigerPor olfactory porePorAp olfactory pore aperturePorW olfactory pore wallPr chitinous process in base of glossaR rod in glossaRi fork of rod in glossaRg ridge on inner side of mandibleS external opening of salivary syringeSC sense cellSCNuc sense cell nucleusSD salivary ductSF sense fiberSkCav cavity in hair socketSMt submentumSS salivary syringeTn fleshy tongue on ventral surface of men-tumTP terminal tip of pharyngeal plateTr tracheaX place on dorsal surface of mentum towhich liquid foods perhaps travel be-fore being swallowed