THE PRESERVATION OF MUSEUM SPECIMENS FROM INSECTS AND
THE EFFECTS OF DAMPNESS.
By Walter Hough, A. M.
The preservation of museum specimens is of no less importance than
their acquisition. Periodically the attack of some new insect, or the
infesting of some new material, is brought to the notice of curators, and
hitherto many specimens have been destroyed which it would be now
impossible to replace. In a great museum the abundance of the mate-
rial will not permit its frequent examination, so that all specimens
should be thoroughly poisoned before they get out of sight. There are
many things which one would not think it necessary to poison, yet all
should be, for nearly all organic structures have peculiar enemies in
the insect world. As instances, woodwork, basketry, textiles, botan-
ical specimens, etc., should be poisoned with corrosive sublimate, as it
coagulates the albuminoid principles in vegetation and thereby pre-
vents decay as well as the attacks of insects.
The ravages of moths have been experienced from remote times, and
though the preservation of materials from the attacks of these and other
insects has been repeatedly attempted, all efforts, it seems, have so far
been ineffectual. Most of the chemical substances suggested are too
poisonous to be used on articles brought in contact with the person,
as in every-day wear. Happily this is no objection here, for with ordi-
nary precautions the specimens sent to the Museum can be treated with
the strongest poisons, the main difficulty being to avoid damaging the
material in their application.
First in rank of destructiveness are the moths, of which four species
have been observed at active work in the Museum. These are Tinea
flavifrontella Linn., the common, or clothes, moth; T. tapetzella Linn. , or
carpet moth; T. pellionella Linn., or fur moth, and T. granella Linn., or
grain moth. These Tineids are night-flying insects, though the little
fluttering « millers w are often seen flying in darkened rooms in the day-
time. Their natural habitat is in dry animal and fibrous vegetable sub-
stances, and sometimes on the fur of living animals ; in houses they
infest woolens, furs, grain, etc., and the destruction caused by the larvae
is well known. They begin to fly about actively in May. I have ob-
served them in warm rooms as early as March, and have found the
larvae, all through the winter. In the stage in which this insect does
549
550
its destructive work, it is a plump white caterpillar provided with strong
mandibles and sixteen legs. It nips the fiber, beginning as soon as
hatched from the Qgg, and builds a case which is enlarged as the insect
grows. These insects are known to travel in search of other quarters;
they are very hard to kill, extreme cold does not affect them, and many
of the domestic preventives, such as camphor, tobacco, etc., entirely fail
to destroy them.
All articles subject to injury from these moths should be often exam-
ined and shaken, especially in spring and early summer, to dislodge
the eggs.
Another very serious pest is the " buffalo bug" (Anthrenus lepidus
Linn.), and its relative the " carpet bug" (A. varius Fabr.). The adult
is a small round sluggish beetle, brown, with white or variegated scales
on the wing covers. The larva? are short, plump worms with numer-
ous stiff, brown hairs. This insect is on the increase ; its ravages seem
to have attracted the notice of the public, and much was written about
it a few years ago, in 1882 and 1883. Like the tinea larva, the buffalo-
bug larva cuts leather, woolen, or fur, and builds an incoherent case
from the fragments. These insects multiply very rapidly, and are also
unaffected by ordinary insect preventives.
The larvae of the "basket beetle" (Sitodrepa panicea Linn.) are small
worm-like creatures with six minute feet. They are furnished with
strong cutting-jaws by means of which they eat their way into basketry
and old wood, or similar substances, boring little holes as round as if
made with a fine drill. The adult insect is a little, sluggish, brown
beetle which simulates death on being disturbed.
Another insect, the subject of a letter to Science, May 28, 1886, and
there called "A New Museum Pest," is the "silver fish" (Lepisma domes-
tied). The adult is a shining fish-shaped insect, wingless, but very quick
in its movements. It prefers starch for food, and attacks everything
that contains that substance, such as labels pasted or sized with starch
or mucilage, cotton or linen laundered goods, etc. This insect is ex-
tremely obnoxious to librarians, being attracted by the paste used in
binding books.
Other insects are often introduced into the Museum on specimens and
by other means, but these are of less consequence, as they do not breed
there and are usually not harmful.
It has been thought well to introduce here a paper by Mr. John B.
Smith, assistant curator of entomology in the Museum, relating to the
care of insect collections. It was published in the Proceedings of the
Entomological Society of Washington,* under the title "Some Observa-
tions on Museum Pests."
One of the duties of a person in charge of a large collection of insects is keeping
out museum pests, as the various species that feed on the dried insects are generically
called. In a large collection, like that of the National Museum, no inconsiderable
'Vol. i, No. 2, p. 113.
PRESERVATION OF MUSEUM SPECIMENS. 551
time is required for that purpose, as it takes at least two weeks to go through all the
boxes carefully.
It has beeu the fashion to recommend as a certain preventive tight boxes, and
quarantining all specimens before putting into the collection, and undoubtedly this
is an excellent precaution, saving much future labor. It is, however, by no means
the certain remedy it has been claimed to be. The boxes and cabinets in use in the
Museum are as perfect, as far as safety is concerned, as it is possible to get them at
present, yet withal constant care is required. Psocidw will find their way into the
tightest boxes, and though they do little damage ordinarily, yet in a collection of
Tineidcv, or minute Diptera, they can do considerable damage. For these pests I have
found naphthaline a perfect remedy. A single half-ounce cone is a perfect protection,
and lasts about three months ordinarily.
Tineid larva? are rather rarely found in the collections on the larger moths, and
are not always easily discovered, since they make no dust, as do the Anthreni. On
one occasion I found that one pair of wings of a C. regalis suddenly collapsed with-
out apparent cause. Close examination showed a Tineid larva that had been feeding
on the dense, long vestiture, making galleries in all directions in such a way that
when I took hold of one end of the gallery, the vestiture of the under side came off
in large sheets, leaving the wings almost clean, the veins broken here and there,
which produced the collarnse. They rarely burrow into the specimen, never in my
experience. Ptinidce are sometimes found, but are exceedingly rare in our collection.
One box lined with corn pith was riddled by them, and a very few specimens were
attacked. By all odds the most dangerous enemies are the larvae of the Dermestidw,
which are pests pure and simple. The principal enemy in our collection is Anthrenus
varius, though Trogoderma is not uncommon.
My experience with these is, that in the uniformly high temperature preserved in
the laboratory they breed all the year around, and have no definite broods; a few
larvae appear at all times, though during the summer, when the beetles come in from the
grounds, and from other parts of the Museum, exposed specimens are attacked at more
regular intervals. The rule is to keep naphthaline in all boxes at all times, but, like
all rules, it is not always possible to adhere strictly to it. The boxes not so protected
are usually first attacked. In a cabinet not quite tight I coned a number of drawers
and left the others unprotected. In the course of the summer the unprotected drawers
nearly all became infested, while as a rule the others were free. The naphthaline
seems to act as a repellaut. I have found, however, that it does not annoy the larvae
to any very great extent, and Mr. Lugger has shown me a naphthaline cone in a hol-
low of which a larva had pupated. I have reason to believe, however, that it does re-
tard the development of young larvae. A large number of boxes, nearly one hundred,
were received from North Carolina, containing a collection, principally Coleop-
tera. They were overhauled and found to be pretty generally infested with Trogo-
derma, this being the only species found. No Anthrenus larvae were noticed. Bisul-
phide of carbon was freely used, and naphthaline cones were placed in all the boxes.
For awhile the boxes were frequently examined and no larvae developed. Through-
out the summer the boxes were examined at intervals and remained free. With the
approach of cold weather they were left for a longer period and the cones nearly all
evaporated. In December this was noticed, and the boxes were again overhauled,
and it was found that a very general development of larvae had begun, all of them
Trogoderma, and none of them more than 2 to 3 millimeters in length, most of them
apparently just hatched. The entire collection was scrutinized, and an occasional
Anthrenus larva was found, but no other Trogoderma, even in the most exposed boxes.
I conclude from this that the collection when received was infested, and that there
were e{ gs everywhere ready to develop ; some had begun to develop, and these were
destroyed by the use of bisulphide of carbon, which also served to check the develop-
ment of the eggs. The boxes were quite large, and two large cones were put in each
;
they were also quite secure, and the atmosphere in them was fully impregnated with
552 REPORT OF NATIONAL MUSEUM, 1887.
the odor of naphthaline. Throughout the summer, when under ordinary circumstances
they would have developed, the egg3 remained dormant, but after the naphthaline had
evaporated completely, development began. I might add here that Trogoderma is an
exceedingly rare pest in New York, and not common in Washington ; farther south it
seems to replace Anthrenus. For all these pests bisulphide of carbon is a sovereign
remedy, except when they are burrowing in large Coleoptera or Lepidoptera. I have
repeatedly soaked large Bombycids with chloroform or bisulphide, and a week later
found them still infested. I worked for a month over some large Lucanids (Procule-
jus), and finally separated the parts so that I could fill the body cavity with chloro-
form. In one case, that was somewhat exposed and contained old material of little
value, I found a specimen destroyed by Microgaster, a rare parasite for Anthrenus.
How they got at this box is difficult to explain, since it was tight enough to prevent
the entrance of the insect.
I have noticed also that boxes on the lower tier of shelves are much more liable to
attack than those on upper tiers, and this leads me to believe that the parent beetle
will deposit eggs outside of the boxes or on the floor of the cases, and the young larva)
will work their way into the smallest crevices. It seems difficult to account for iso-
lated larva3 in boxes containing only old insects.
Finally I find the danger of infection comparatively greater at Washington than
in New York, principally because the warm season begins earlier and lasts longer, in-
creasing the chances of infection. I find, too, that the only real chance of safety con-
sists in constant examination, tight boxes, and a free use of chloroform or bisulphide
of carbon.
As to naphthaline, I consider that it is a good general preventive. I know that
it keeps out Psocids and ants. It enhances the tendency to grease and to verdigris,
and in tight boxes it seems to exercise a relaxing tendency, causing the wings to
droop.
There are several classes of substances to be poisoned, in which the
colors, fabric, or character of material, and therefore the kind of poison
and the strength of solution, are important factors. For instance, goods
not fast dyed (especially cotton), or which are dyed with colors that
contain solutions, will start ; also fabrics or substances which may be
corroded or hardened, or otherwise injured, as feathers, fur, dressed
deer-skin, etc. Too strong a solution may also cause a deposit on fur,
etc., with a dulling effect. As a test for this, a black feather should be
dipped in the solution, if it is of corrosive sublimate or arsenic in alcohol.
If the solution be too strong, it will produce a white coating when dry.
Any solution should exert its action in two ways, first to repel the adult
insect, and second, to destroy the hatched larva. Pungent odors are
noxious to moths and the higher orders of insects, but this is hardly
true in the case of the beetles to which we have before alluded. The
pungency of odor can not be made to last long, so that the poisoning
quality is of prime importance. The substances used for solutions are
deadly poisons, and no one who has not had experience in handling
them had better undertake to apply them. Corrosive sublimate will
attack the finger-nails and the skin. It is also volatile. Arsenic is
prejudicial to the health; the dust, it is said, produces catarrh, both
gastric and nasal, though this has not been confirmed by my observa-
tion.
Before poisoning, all objects should be treated with benzine, by put-
PKESERVATION OF MUSEUM SPECIMENS. f)53
ting them in a close box or vessel, and pouring* the benzine in, leaving
them tightly closed therein for several days. This operation destroys
any larvae or eggs. They should then be hung up until the benzine
evaporates before proceeding with the poisoning solutions. Bisulphide
of carbon is more volatile and more quickly effective than benzine, and
may be used, if preferred. There is reason to believe that both kill the
eggs
—
quickly if the fluid comes in contact with th«,m and less rapidly
if they are directly affected only by the fumes in the vapor. Great care
must be taken not to allow fire of any kind to come in contact with the
vapor of bisulphide of carbon. There are several reasons why benzine
is preferable, and the latter is sure to be effective when followed by
the arsenic-naphtha solution. The solution found most satisfactory for
poisoning nearly every kind of specimens is as follows:
Saturated solution of arsenic acid and alcohol 1 pint.
Strong carbolic acid 25 drops.
Strychnine 20 grains.
.Alcohol (strong) 1 quart.
Naphtha, crude or refined 1 pint.
The use of strychnine is not absolutely necessary ; but it is a very good
agent and adds much to the value of the solution. Other solutions and
poisons will be noticed below. It will be found advisable to apply solu-
tions in the form of spray to delicate objects, such as feathers or speci-
mens of similar character. In this treatment an atomizer may be used.
Some small specimens may be dipped and allowed to drain, and the
solution may be applied with a brush to a large class of objects, taking
care to saturate every part. The specimens can then be hung up to dry
or laid away as they are. They should be kept free from dust, which
is exceedingly injurious to them. As soon as poisoned, they ought, if
intended for exhibition, to be mounted in dust-tight cases, or carefully
stowed away in close-fitting drawers or boxes. In unit or costume
boxes a small packet of naphthaline may be concealed behind the speci-
mens, and the junction of the lid should be made dust-proof by pasting
on strips of paper with paste containing arsenic or corrosive sublimate.
Some specimens present problems that do not fall under any rule and
have to be left to judgment and experiment. As an instance in point,
we mention a fine deer-skin robe collected by Mr. Turner, beautifully
tawed, with the hair on, and ornamented with a medium which will not
stand wetting. It is obvious that no solution can be used in this case,
since alcohol or water will harden the buck-skin and destroy the decor-
ation. Satisfactory results might be obtained by judicious spraying,
but there would be doubt as to the completeness of the poisoning. It
would be better to rub into the kid surface a powder made of precipi-
tated chalk and white arsenic. The fur side should then be well rubbed,
care being taken to allow the powder to penetrate into the roots of the
hair. By all means protect the hands with gloves. Powdered soap
would also be a good medium for the arsenic. Great care should be
554 REPORT OF NATIONAL MUSEUM, 1887.
taken in applying this poison and in handling a specimen poisoned in
this way. Such specimens should be at'once closed up tightly and put
on exhibition.
Corrosive sublimate has been much used for poisoning and is a valu-
able agent. Several specimens in the Museum, which were poisoned
years ago with this substance, were so filled with it that they are dusty.
They are made of fur-skin, and are stiff and unpresentable for exhibi-
tion. I do not know what was the condition of the articles wheu they
were acquired ; they are, however, undeniably moth-proof. I have found
numerous adult moths destroyed in the act of laying their eggs. A care-
ful use of corrosive sublimate is very effective, if it is not brought in con-
tact with skins, as it coagulates albumen. It is also volatile, and Dr. G.
H. Beyer, U. S. Navy, has proposed to take advantage of this property
in preventing the growth of fungi on materia-medica specimens in jars.
One objection to corrosive sublimate is that it crystallizes out very
easily ; this might be obviated by adding a little naphtha to the alco-
holic solution.
Naphthaline is used by Mr. J. B. Smith, of the Museum, and by other
entomologists, to preserve insect collections from Acari, Psoci, Dermes-
tes, Anthreni, and other museum pests.* It destroys the two former,
but only tends to repel the others. It also acts as an antiseptic, de-
stroying schizomycetes, moulds, bacteria, etc. The salt is perfectly neu-
tral, is not poisonous to man, and is cheap. It is customary in this
department to put a small packet or cones in cases containing mounted
costumes.
Vaseline may be called perfect grease, since it does not become ran-
cid or corrosive. It is especially useful to protect iron and steel from
rust, and no doubt would preserve woodwork from extraneous attack.
It is also good to soften leather which has become hard. In the case of
clubs, spears, and implements of hard wood, like those of Polynesia, a
fine polish may be obtained by using vaseline. I regard vaseline as a
good vehicle in which to apply white arsenic to skins, as is done with
arsenic soap. It penetrates very well, especially if thinned a little with
naphtha. Vaseline is also used on book-backs to soften them, to pre-
vent mould, and to keep insects away.
A few recipes germane to this subject, and which may be useful in
other departments of the Museum, are appended:
Mr. Hornaday has used arsenical soap prepared in the following
manner:
White soap 2 pounds.
Powdered white arsenic 2 do.
Camphor ~ 5 ounces.
Subcarbon ate of potash 6 do.
Alcohol 8 do.
See p. 555.
PRESERVATION OF MUSEUM SPECIMENS. 555
Slice the soap, melt it, add the potash, stir in the arsenic, and add the
camphor previously dissolved in the alcohol. Stir, when cooling, to pre-
vent the arsenic from sinking to the bottom. For use, mix a small
quantity with water until it resembles buttermilk, and apply with a
common paint-brush. This is a mechanical mixture. Mr. Hornaday
has obtained results of the highest order from its use. The following
is believed to be a more correct chemical combination
:
White soap 1 ounce.
Arseniate of potash 2 do.
Water 6 drachms.
Camphor 2 do.
Strychnine (ad lib. ) 15 grains.
The following ingredients make an effective preservative powder
:
White arsenic 1 pound.
Burnt alum 1 do.
Powdered oak hark 2 do.
Camphor -£ do.
This should be powdered well, sifted and kept in well-stoppered bot-
tles. It should be applied to the wet surface of skin and rubbed in
well. The hands should be protected with gloves. I have never tried
this preparation.
The following solution has been prepared by Wickersheimer for the
preservation of objects in the natural state:
Alum 500 grains.
Salt 125 do.
Saltpeter 60 do.
Potash 300 do.
Arsenic trioxide (white arsenic) 100 do.
Dissolve in 1 quart of boiling water. Cool and filter, and for 1 quart
of the solution add 4 quarts of glycerine and 1 quart of alcohol. Either
soak the objects in the solution, or inject them with it. This solution is
said to do very well except in tropical climates.
For botanical specimens this is said to be an excellent preservative
:
One ounce of corrosive sublimate to 1 quart of alcohol, diluted 50
per cent. The best plan is to dip the specimens and then carefully dry
them. The poison can also be painted on with a camel's-hair brush.
For the preservation of entomological specimens, the strongest solu-
tion used should be corrosive sublimate in alcohol, 1 to 100, and the
weakest 0.1 to 100. (See remarks on naphthaline, ante.)
For insects on plants, the following solutions are recommended
:
First solution.
Salt 2| pounds.
Saltpeter 4 ounces.
Water 1 gallon.
Filter.
Second solution.
First solution 1 quart.
Arseniate of potash 2 ounces.
Water ! 1 gallon.
556 REPORT OF NATIONAL MUSEUM, 1887.
.<>•-A cheaper solution can be made by taking
White arsenic : i pound.
Sal soda 4 ounces.
Water 1 gallon.
Boil till a solution is made. Take 1 quart to 40 gallons of water.
These solutions have been found by the Department of Agriculture to
be very useful in destroying the scale-bug and the red spider, so harmful
to plants.
The following method is employed by furriers in the treatment of fur
skins for the purpose of rendering them pliable: The skin is steeped
and scoured in a bath of alum, bran, and salt, in order to remove greas-
iness; then in a bath of soap and soda, to remove the oil from the fur.
When thoroughly washed and dried it is found that the pelt has become
tawed or kid leather.
To soften and cleanse buck-skin or chamois leather, rub plenty of
castile soap into the skin and soak for two hours in a weak solution of
sal soda in warm water and rub well until quite clean. Afterwards rinse
in a weak solution of sal soda and soap in water; after rinsing, Wring it
dry in a coarse towel, and when fully dry beat it until soft and smooth.
For domestic purposes the following preventives from moth ravages
are suggested : Dissolve in 200 parts of alcohol 2 parts of salicylic acid
and 2 parts of thymol; perfume with oil of lemon. This is a neutral
solution and will not injure colors or texture, and has a pleasant odor,
but is rather expensive.
A good preparation to sprinkle among furs being packed away in a
close box or drawer, is naphthaline and menthol or thymol, in proportion
of 1 ounce of the former to 20 grains of either of the latter, rubbed to-
gether. The odomvill disappear from the furs or goods after they have
been aired for a short time. Even if moths are present and are hatched,
they will not feed when closely shut up in the odor of this mixture, and
in this respect it is far superior to camphor. Thymol alone is very good.
Naphthaline is now on the market in a very convenient shape called
" moth marbles," and seems to be going into general use.
In the following list of apparatus only those things have been men-
tioned that have been found necessary or very useful in the operations
at the National Museum. Doubtless at other places, where such a
range of subjects for poisoning is not presented, some of the articles
can be dispensed with
:
Gutta-percha atomizer, which may bought for one dollar. The bottle
can be easily wired to a handle for convenience. (Fig. 1.)
I'ig. 1. Gutta-percha atomizer.
Galvanized sheet-iroivtank (Fig. 2) used for subjecting specimens to
bisulphide of carbon. The lid and air-hole cap on the lid both fit into
PRESERVATION OF MUSEUM SPECIMENS. 557
a slot (Fig. 2a) that is to be filled with water to prevent escape of gas.
The tank should be set out in the open air if possible. The size of the
tank used here is 3 by 2 by 2 feet, and it has handles on the ends and on
the lid. (Fig. 2.)
Fig. 2a. Showing adjustment of lid of tank. Fig. 2. Galvanized sheet-iron tank.
Shaw and Geary No. 2 air compressor (cost $15), and four-nozzle
gutta-percha atomizer, cost $2.50. These are found necessary only
when much spraying is to be done.
Stock solution jar, jar for mixed solution, benzine jar or jug, gradu-
ate, 1 pint; glass funnel, 3 paint brushes, not too large; several stone-
ware jars with closely fitting lids for smaller specimens. With good-
sized jars, or even a closely-joined box, the galvanized tank may be
dispensed with, especially when benzine is to be used.
The poison tags should not be large. They are convenient for show-
ing whether specimens are poisoned or not, and when, and are some-
times a good test whether they are well poisoned. They may be printed
with death's-head and word "poisoned," with space for date and mu-
seum number.
The long established " Museum standard" cases are provided with
beadjand groove (Figs. 3 and 4) which effectually exclude dust and in-
sects, the two worst foes of museum collections. In putting up perish-
y [ j
Fig. 3. Section across back of door. Fig. 4. Section across junction of door.
able specimens permanently in the glazed Museum unit boxes, etc., the
backs are made of tin, and to guard against the minute, insinuating,
newly-hatched moth larva, the junction of the lid with the sides is
pasted over with strips of paper or muslin with glue, poisoned with
corrosive sublimate or arsenic. This, with naphthaline cones inside, is
the highest triumph of the preservation of museum specimens.
558 REPORT OF NATIONAL MUSEUM, 1887.
In the following table are given the approximate prices of chemicals
which have been referred to in this paper:
Alcohol, 95 per ceut $2. 50 per gallon.
Arsenic acid, Merck's 40 per pound.
Arseniate of pot ash do.
Arsenic, white 10 do.
Benzine 15 per gallon.
Bisulphide of carbon .25 per pound.
Burnt alum 10 do.
Camphor 25 do.
Carbolic acid, Calvert's solution 60 do.
Chloroform 75 do.
Corrosive sublimate (mercuric chloride) 90 do.
Ether 85 do.
Glycerine 30 do.
Menthol 50 per ounce.
Naphtha per gallon.
Naphthaline crystals 25 per pound.
Naphthaline cones 1. 25 per 100.
Naphthaline "moth marbles" 10 per box.
Oak bark, powdered, or tannin 10-.25 per pound.
Oil of lemon 20 per ounce.
Salicylic acid 2. 25 per pound.
Saltpeter 35 do.
Sal soda 05 do.
Strychnine 20 per £-ounce.
Subcarbouate of potash 25 per pound.
Thymol
- 60 per ounce.
Vaseline, Cheeseborough's 50 per pound.