Comparative Allometry and Sexual Behavior of Four Fruit Fly
Species in the Tribe Ceratitidini (Diptera: Tephritidae)
R. D. BRICEN?O,1 W. G. EBERHARD,1,2 AND S. QUILICI3
ABSTRACT: Sexual dimorphisms in four related species of tephritid flies were shown to be
associated with differences in sexual behavior. In two species, Ceratitis capitata and C. catoirii, males
and females approach closely head to head and apparently touch aristae, and the male buzzes his
wings, probably fanning pheromone toward the female; the males were found to have longer aristae
with fewer microsetae, and larger posterior areas of their wings than do females. These dimorphisms
were absent in the other two species, C. rosa and Neoceratitis cyanescens, which court at a longer
distance and in which the male does not fan pheromone toward the female prior to mounting. All three
pairs of legs were proportionally longer in the males of all four species. None of the other sexually
dimorphic male signalling traits showed the positive allometric slopes predicted by some theories.
KEY WORDS: Ceratitis, Neoceratitis, sexual dimorphism, sexual selection, courtship
Sexual selection often results in differences between male and female traits. In some cases
the proportional sizes of traits remain the same, and it is only the overall body size that
differs between males and females. In others, the proportional sizes of traits differ. Male
structures that are used as signaling devices and as weapons are frequently not only larger in
males than females, but also proportionally larger in larger males of a given species (Huxley,
1972; Petrie, 1988, 1992; Alatalo et al., 1988; Green, 1992; Baker and Wilkinson, 2001).
The proportional size of a trait is often expressed as the slope of the log-log regression of that
trait vs. the overall body size in mature conspecific individuals: when the slope is .1.0
(??positive allometry??), larger-sized individuals have proportionally larger structures.
The reason why sexually selected traits tend to show positive allometry is not certain
(Huxley, 1972; Petrie, 1988, 1992; Green, 1992). Baker and Wilkinson (2001) suggested
that sexually selected traits which serve as ornaments or weapons are relatively small in
smaller individuals because small individuals have less to gain from investing in such
structures. Otte and Stayman (1979) proposed a related, ??overflow?? model, in which
larger individuals have proportionally greater reserves of material which they can dedicate
to sexually selected traits. Petrie (1988) argued that only structures used as signaling
devices in intraspecific aggression should show positive allometry, and that weapons
should not show positive allometry. This idea is not supported empirically, however.
Positive allometry is commonly observed in the horns of mammals and beetles and the
cerci of earwigs, which are known to function as weapons in intraspecific battles between
males. In some of these groups behavioral details and the settings of interactions suggest
that they function as weapons rather than in displays (Huxley, 1972; Eberhard, 1979;
Brown, 1980; Eberhard and Gutierrez, 1991; Bricen?o and Eberhard, 1985; Eberhard et al.,
1998, 2000 ). Bonduriansky and Day (2003) suggested that positive allometry is expected
in both signals and weapon traits only under certain sets of conditions.
1 Escuela de Biolog??a, Universidad de Costa Rica, Ciudad Universitaria, Costa Rica; e-mail: rbriceno@
biologia.ucr.ac.cr
2 Smithsonian Tropical Research Institute; e-mail: archisepsis@biologia.ucr.ac.cr
3 CIRAD Re?union, UMR ??Peuplements Ve?ge?taux et Bioagresseurs en Milieu Tropical?? (PVBMT), Po?le de
Protection des Plantes, Saint-Pierre, France.
Accepted 29 April 2004; revised 21 August 2004

 2005 Kansas Entomological Society
JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY
78(1), 2005, pp. 20?33
Behavioral observations of how particular structures are used are needed to interpret
their allometric patterns of morphology. Very little is known regarding the sexual biology
of flies in the genus Ceratitis, aside from that of the widespread pest species, C. capitata
[Wiedemann] (reviewed in Eberhard, 2000). In C. capitata, males lure females to leks with
pheromones, and court them face-to-face at close range, apparently utilizing visual and
chemical stimuli, as well as tactile stimulation with their antennal aristae (Eberhard, 2000;
Bricen?o and Eberhard, 2002b). Quilici et al. (2002) gave brief descriptions of some aspects
of courtship in the Mascarene fruit fly, C. catoirii Gue?rin-Me`neville, and the Natal fruit fly
C. rosa Karsch. In this paper we present further details of the sexual behavior of three
species of Ceratitidini that damage crops on Reunion Island: two polyphagous species (C.
catoirii and C. rosa), and the stenophagous Tomato fruit fly, Neoceratitis cyanescens
(Bezzi), which attacks wild and cultivated Solanaceae. We also correlate these obser-
vations with patterns of sexual dimorphism.
Methods
Flies of C. rosa and N. cyanescens used for behavioral and morphological observations
were first generation descendants of wild flies from Reunion Island. Adults from a recent
lab-rearing were used for the more rare C. catoirii. Measurements of C. capitata were
made using flies from an approximately five year-old mass-reared strain derived from wild
flies in Costa Rica. Video recordings of courtship behavior of C. catoirii, C. rosa, and N.
cyanescens strains that had been in captivity only a few (,5) generations were made on
Reunion Island with an analogue video camera using standard techniques (e.g., Bricen?o
and Eberhard, 2002a), and were analyzed frame by frame.
Measurements of legs, wings, and bristles (Fig. 1?terminology of White et al., 2000)
were made by mounting structures flat on microscope slides in Hoyer?s medium, and
photographing them using a Sanyo VCC-3912 camera mounted on a compound micro-
scope and connected to a Genius Video Wonder Series II card in a computer. Measure-
ments were made employing the Scion image program (
 1998 Scion Image Corp.).
Thorax length and head width were measured in dorsal view when the posterior edge of
the thoracic scutellum just obscured the posterior edge of the mediotergite (terminology
of White et al., 2000). When all measurements were repeated on 20 individuals of
C. capitata to test measurement precision, correlations between first and second mea-
surements ranged from 0.93 to 1.0.
Tests for differences in log-log plots of different traits against thorax length were
performed by first testing for differences in male and female centroids with Wilk?s Lambda
tests. Differences in male and female slopes and elevations of ordinary least squares (OLS)
regressions were tested as described by Zar (1999). OLS regressions were used instead of
reduced major axis (RMA) regressions, which generally give somewhat higher slopes
(Green, 1999; Eberhard et al., 1999). RMA analyses are preferred by some authors (Green,
1999), but are not clearly more appropriate for the type of analysis performed here (see
discussion by Eberhard et al., 1999). Means are followed by 6 one standard deviation.
Results
Behavior
Ceratitis catoirii
Males in field cages apparently called females pheromonally in the morning, inflat-
ing their abdominal pleura and everting a spherical body at the tip of the abdomen
VOLUME 78, ISSUE 1 21
(presumably the inflated rectal epithelium, as in C. capitata). Courtship began when
a female approached a calling male. Nine video recordings of courtships in which the male
eventually mounted the female were analyzed. As noted by Quilici et al. (2002), male
behavior resembled that of male C. capitata, and included continuous wing vibration while
the male faced the female early in courtship, and intermittent wing buzzing later after the
female approached closer. The flies approached closely, to within about 0.25 body lengths,
before the male jumped onto the female. This was close enough for contact to occur
between their aristae, as in C. capitata (Bricen?o and Eberhard, 2002b), but the aristae were
not visible in the video recordings. Head rocking behavior similar to that of C. capitata did
not occur. As in C. capitata, the female turned to look more directly at the male during the
Fig. 1. Dimensions of measured structures: (A) (a?f) leg; (B) (g?i) supra-fronto-orbital (SFO) seta (of male C.
capitata and C. catoirii); and (j?k) wings of male (C) and female (D) C. catoirii, and male (E) and female (F) C.
rosa. a?length femur; b?length tibia; c?length longest tibial seta; d?length brush of tibial setae (only the
most basal, most distal, and longest setae are drawn); e?length tibia from base of brush; f?length longest
femoral seta; g?widest portion of tip on left side of center line; h?length of seta; i?widest portion of tip on
right side of center line (width of tip? g? i); j?width of wing; k?length of wing. The area of the discal (DB)?
apical band (SAB) (1) on the wing was measured; two other bands, the anterior apical band (2) and the posterior
apical band (3) were not measured. Scale bars are 0.2 mm for leg (A), 0.1 mm for bristle (B), and 1.0 mm for
wings (C?F).
22 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY
latter stages of courtship. Durations, distances, and angles at different stages of courtship,
which reflect both male courtship and female responses (Bricen?o and Eberhard, 2002a),
were at least generally similar in the two species (Table 1).
Ceratitis rosa
Male C. rosa in field cages formed small groups (usually 2?5 males), especially late in
the afternoon, either on fruit where females might oviposit, or on leaves. They appeared to
call females pheromonally, inflating their abdominal pleura and everting a tri-lobed rectal
ampulla. Fourteen video recordings confirmed the general descriptions of Quilici et al.
(2002). The male responded to an approaching female by performing continuous wing
vibration. Males did not perform intermittent wing buzzes or head rocking as in C.
capitata, but the male faced toward the female (8.0 6 13.68) while the female faced less
directly toward the male (18.1 6 18.28) just before he jumped. The male extended his
middle legs laterally very briefly (0.1?0.2 sec) just before jumping onto the female. In ten
cases the male first extended one leg, withdrew it, and then extended both legs just before
jumping. In two others he twice extended both legs briefly, and in two others he extended
each one, in alternation, just before jumping. The distance between male and female at the
moment the male jumped was larger than that in C. capitata and C. catoirii (mean? 1.3 6
0.5 body lengths, N? 9).
Table 1. Comparison of courtship behavior in C. catoirii (this study) and successful courtships of wild male
C. capitata (A from Bricen?o and Eberhard, 2002a, N ? 34; B from Bricen?o and Eberhard, 1998, N ? 22).
Differences in experimental settings and small sample sizes make statistical comparisons inappropriate.
C. catoirii C. capitata
Durations (sec)
Continuous vibrate wings 5.15 6 4.21 18.7 6 23.8 (A)
Intermittent buzzing wings 17.0 6 10.2 10.7 6 6.6 (A)
Number of buzzes/courtship 35.8 6 9.9 41.8 6 39.0 (B)
Rate of buzz (number/sec) 2.34 6 0.56 4.5 6 1.7 (B)
Total courtship before mount 21.5 6 13.2 23.2 6 22.2 (A)
Female immobile before mount 4.87 6 1.57 5.78 6 3.63 (A)
Distances (fraction of male length)
Start of continuous wing vibration 1.50 6 2.08 1.36 6 0.81 (A)
Start of intermittent wing buzz 0.45 6 0.14 0.30 6 0.12 (A)
Jump onto female 0.25 6 0.07 0.14 6 0.02 (A)
Angles
Male orientation toward femalea
Start of continuous vibration 7.4 6 8.88 10.2 6 9.28 (A)
Start of intermittent buzzing 4.3 6 5.38 2.8 6 3.68 (A)
Moment of jump 3.1 6 5.98 1.1 6 2.18 (A)
Female orientation toward maleb
Start of continuous vibration 31.5 6 37.88 52.6 6 33.28 (A)
Start of intermittent buzzing 8.9 6 13.58 7.3 6 9.98 (A)
Moment of jump 4.1 6 6.98 3.9 6 4.28 (A)
N 9 34, 22
a 08 ? male facing directly toward female.
b 08 ? female facing directly toward male.
VOLUME 78, ISSUE 1 23
Neoceratitis cyanescens
Only three courtship sequences were taped, and only two of these led to mounting. In all
three the male made rhythmic, small amplitude anterior-posterior synchronous movements
with his wings (low amplitude ??enanation?? in the terminology of White et al., 2000) while
the female was several body lengths away, and in two of the three it was clear that there
was a brief burst of low amplitude buzzing each time the wings moved anteriorly. At no
time did the male perform either continuous wing vibration or intermittent buzzing similar
to that seen in the other species. In one case the female approached the male even though
(in sharp contrast with the other species) he did not turn to face toward her (the male?s
angle was about 908 when he jumped). The distance between the two flies at the moment
the male jumped onto the female was between two and three body lengths, much greater
than ever seen in several hundred mounts we have observed in published and unpublished
studies of C. capitata. The male did not extend any of his legs laterally before jumping, as
in C. rosa.
Morphology?Sexual Dimorphism and Allometry
Tables 2a?d present measurements of male-female dimorphism in overall size and
allometry, and Table 3 summarizes the sexual dimorphisms in the different species.
Female body size (estimated by thorax length) was larger than that of males in C. capitata
and C. rosa, but not in C. catoirii and N. cyanescens.
The expanded supra-frontal-orbital (SFO) bristles of males differed between C. capitata
and C. catoirii. Those of C. capitata were much shorter (means were 0.38 6 0.03 and
1.15 6 0.10 mm respectively), and had narrower expansions at their tips (mean widths
were 0.22 6 0.02 and 0.76 6 0.06 mm respectively) (both P , 0.01 with t-tests). The
log-log slopes of length and width on body size were relatively low in both species
(respectively, 0.28 and 0.26 in C. capitata, and 0.27 and 0.42 in C. catoirii; only the final
value was statistically significant, P ? 0.03).
The length of the longest dark setae on the dorsal or the ventral side of the tibia II in the
tibial brush of male C. rosa were not significantly related to male body size. The log-log
slopes on body size were 0.24 and 0.48 respectively (P . 0.2 in both cases). The length of
the brush, measured at the bases of the setae on the dorsal surface of the tibia (d in Fig. 1A)
had a weak, positive relationship with body size (log-log slope ? 0.51, P? 0.02).
Discussion
Several patterns in the most highly significant male-female differences in morphology
(P , 0. 001 and ,0.0001 in Tables 2 and 3) are in accord with apparent differences in
sexual behavior (increased behavioral samples, especially in N. cyanescens, are needed to
confirm the patterns we note here). In the two species in which males and females
approached each other head-to-head to within about 0.25 body lengths before the male
mounted (C. capitata and C. catoirii), the length of the male?s arista was greater than that
of the female, and the male arista had fewer microsetae (as also found in C. capitata by
Miranda, 2000). Tactile stimulation from the male aristae is apparently important to induce
female C. capitata to mate (Bricen?o and Eberhard, 2002b), and the similar allometry of
male aristae in C. catoirii suggests that they play a similar role in this species. The aristae
were not sexually dimorphic in C. rosa and N. cyanescens, in which males and females did
not approach close enough prior to mounting for their aristae to touch.
24 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY
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VOLUME 78, ISSUE 1 25
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.1
5
0.
13
ns

0.
05
fe
m
al
e
1.
17
6
.1
1
**
*
0.
45
*

0.
29
**
**
ns
**
**
nu
m
be
r
do
rs
al
se
ta
e
ar
is
ta
m
al
e
7.
64
6
6.
82

0.
17
ns
2.
22
fe
m
al
e
26
.3
7
6
7.
78
**
*
0.
20
ns
0.
73
**
**
ns
**
*
nu
m
be
r
ve
nt
ra
l
se
ta
e
ar
is
ta
m
al
e
0.
00
fe
m
al
e
5.
10
6
3.
38
**
*

0.
16
ns
1.
56
?
?
?
le
ng
th
w
in
g
m
al
e
4.
2
6
.5

0.
33
ns
0.
74
fe
m
al
e
4.
4
6
.1
**
*
0.
64
**
**
0.
36
**
*
**
*
**
w
id
th
w
in
g
m
al
e
2.
77
6
.4
2

0.
18
ns
0.
50
fe
m
al
e
2.
38
6
.1
0
**
*
0.
58
**
0.
09
**
**
**
**
**
po
st
er
io
r
ar
ea
w
in
g
m
al
e
2.
55
6
.2
2

0.
47
*
0.
84
fe
m
al
e
2.
15
6
.1
7
**
*
0.
66
**
**

0.
26
**
**
**
**
**
**
to
ta
l
ar
ea
w
in
g
m
al
e
5.
24
6
.3
9
0.
68
**
*
0.
78
fe
m
al
e
4.
81
6
.3
5
**
*
0.
52
*
0.
31
**
**
ns
**
**
26 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY
T
ab
le
2.
C
on
tin
ue
d.
M
ea
n
6
SD
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
be
tw
ee
n
m
ea
ns
L
og
-l
og
re
gr
es
si
on
on
le
ng
th
of
th
or
ax
Si
gn
ifi
ca
nc
e
of
W
ilk
?s
L
am
bd
a
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
sl
op
es
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
el
ev
at
io
ns
Sl
op
e
Si
gn
ifi
ca
nc
e
of
sl
op
e
In
te
rc
ep
t
ar
ea
w
in
g
ba
nd
s
D
B
?
SA
B
m
al
e
1.
10
6
.0
8

0.
14
ns
0.
17
fe
m
al
e
1.
12
6
.0
9
ns
0.
10
ns

0.
03
ns
ns
ns
le
ng
th
fe
m
ur
I
m
al
e
1.
41
6
.0
6
0.
65
**
**

0.
13
fe
m
al
e
1.
26
6
.0
5
**
*
0.
50
*

0.
13
**
**
ns
**
**
le
ng
th
se
ta
fe
m
ur
I
m
al
e
0.
57
6
.0
3
0.
33
ns

0.
43
fe
m
al
e
0.
44
6
.0
4
**
*
0.
36
ns

0.
72
**
**
ns
**
**
ar
ea
se
ta
fe
m
ur
I
m
al
e
27
96
6
39
5
0.
22
ns
3.
09
fe
m
al
e
22
09
6
35
0
**
0.
29
ns
2.
77
**
**
ns
**
**
nu
m
be
r
se
ta
fe
m
ur
I
m
al
e
14
.0
0
6
1.
60

0.
22
ns
1.
41
fe
m
al
e
10
.1
5
6
1.
26
**
*
0.
19
ns
0.
69
**
**
ns
**
*
le
ng
th
tib
ia
I
m
al
e
1.
23
6
.1
0
0.
32
ns

0.
16
fe
m
al
e
1.
09
6
.0
7
**
*
0.
62
**
**

0.
39
**
**
ns
**
**
le
ng
th
fe
m
ur
II
m
al
e
1.
51
6
.0
4
0.
49
**
*
0.
03
fe
m
al
e
1.
45
6
.0
7
**
0.
60
**
*

0.
09
**
**
ns
**
**
le
ng
th
tib
ia
II
m
al
e
1.
66
6
.0
6
0.
31
ns

0.
09
fe
m
al
e
1.
56
6
.0
5
**
*
0.
53
**
0.
02
**
**
ns
**
**
le
ng
th
fe
m
ur
II
I
m
al
e
1.
42
6
.0
5
0.
37
ns
0.
00
6
fe
m
al
e
1.
42
6
.0
5
ns
0.
56
**

0.
10
ns
ns
ns
le
ng
th
tib
ia
II
I
m
al
e
1.
37
6
.0
6
0.
39
*

.0
4
fe
m
al
e
1.
34
6
.0
4
ns
0.
58
**

0.
12
**
ns
**
c.
C
.
ro
sa
(N
?
28
?3
0
fo
r
fe
m
al
es
,
22
?3
0
fo
r
m
al
es
)
le
ng
th
th
or
ax
m
al
e
2.
43
6
.0
8
fe
m
al
e
2.
55
6
.1
1
**
*
w
id
th
he
ad
m
al
e
1.
93
6
.0
5
0.
69
**
**
0.
07
fe
m
al
e
1.
98
6
.0
6
**
0.
77
**
**
0.
07
ns
ns
ns
le
ng
th
ar
is
ta
m
al
e
0.
97
6
.1
2
0.
27
ns

0.
51
fe
m
al
e
0.
99
6
.1
1
*
0.
25
ns

0.
27
ns
ns
ns
nu
m
be
r
do
rs
al
se
ta
e
ar
is
ta
m
al
e
41
.8
7
6
5.
51
0.
23
ns
1.
25
fe
m
al
e
41
.2
7
6
5.
47
ns
0.
16
ns
1.
41
ns
ns
ns
VOLUME 78, ISSUE 1 27
T
ab
le
2.
C
on
tin
ue
d.
M
ea
n
6
SD
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
be
tw
ee
n
m
ea
ns
L
og
-l
og
re
gr
es
si
on
on
le
ng
th
of
th
or
ax
Si
gn
ifi
ca
nc
e
of
W
ilk
?s
L
am
bd
a
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
sl
op
es
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
el
ev
at
io
ns
Sl
op
e
Si
gn
ifi
ca
nc
e
of
sl
op
e
In
te
rc
ep
t
nu
m
be
r
ve
nt
ra
l
se
ta
e
ar
is
ta
m
al
e
27
.3
3
6
3.
44
0.
02
ns
1.
39
fe
m
al
e
28
.9
3
6
4.
33
ns

0.
03
ns
1.
50
ns
ns
ns
le
ng
th
w
in
g
m
al
e
4.
19
6
.1
4
0.
71
**
**
0.
33
fe
m
al
e
4.
28
6
.1
2
**
0.
66
**
**
0.
46
ns
ns
ns
w
id
th
w
in
g
m
al
e
2.
39
6
.1
1
0.
57
**
**
0.
06
fe
m
al
e
2.
43
6
.0
8
ns
0.
59
**
**
0.
22
ns
ns
ns
po
st
er
io
r
ar
ea
w
in
g
m
al
e
1.
95
6
.1
6
0.
63
**
*

0.
35
fe
m
al
e
2.
07
6
.1
2
*
0.
50
**
0.
05
ns
*
ns
to
ta
l
ar
ea
w
in
g
m
al
e
4.
54
6
.3
7
0.
68
**
**

0.
03
fe
m
al
e
4.
75
6
.2
7
*
0.
66
**
**
0.
32
ns
*
ns
ar
ea
w
in
g
ba
nd
s
D
B
?
SA
B
m
al
e
0.
50
6
.0
4
0.
45
*

0.
73
fe
m
al
e
0.
66
6
.0
6
**
*
0.
28
ns

0.
44
**
**
ns
**
**
le
ng
th
fe
m
ur
I
m
al
e
1.
22
6
.0
5
0.
40
*

0.
09
fe
m
al
e
1.
17
6
.0
57
**
0.
55
**

0.
18
**
**
ns
**
**
le
ng
th
se
ta
fe
m
ur
I
m
al
e
0.
29
6
.0
2
0.
25
ns

0.
82
fe
m
al
e
0.
31
6
.0
2
**
0.
31
ns

0.
68
*
ns
*
ar
ea
se
ta
e
fe
m
ur
I
m
al
e
12
20
6
30
0
0.
30
ns
2.
01
fe
m
al
e
15
80
6
24
0
**
*
0.
40
*
2.
61
**
ns
**
nu
m
be
r
se
ta
e
fe
m
ur
I
m
al
e
8.
10
6
1.
27

0.
04
ns
0.
98
fe
m
al
e
8.
47
6
1.
50
ns

0.
05
ns
0.
98
ns
ns
ns
le
ng
th
tib
ia
I
m
al
e
1.
10
6
.0
4
0.
53
**

0.
16
fe
m
al
e
1.
03
6
.1
4
**
*
0.
14
ns

0.
02
**
**
ns
**
**
le
ng
th
fe
m
ur
II
m
al
e
1.
60
6
.0
6
0.
70
**
**

0.
10
fe
m
al
e
1.
59
6
.0
6
ns
0.
67
**
**

0.
04
**
**
ns
**
**
le
ng
th
tib
ia
II
m
al
e
1.
65
6
.0
5
0.
69
**
**

0.
04
fe
m
al
e
1.
51
6
.2
6
**
*

0.
03
ns
0.
27
**
**
ns
**
**
w
id
th
tib
ia
II
m
al
e
0.
26
6
.0
2
0.
21
ns

0.
75
fe
m
al
e
0.
24
6
.0
1
**
*
0.
15
ns

0.
67
ns
ns
**
**
le
ng
th
fe
m
ur
II
I
m
al
e
1.
51
6
.0
5
0.
50
**

0.
02
fe
m
al
e
1.
48
6
.0
6
*
0.
44
*
0.
02
**
**
ns
**
**
28 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY
T
ab
le
2.
C
on
tin
ue
d.
M
ea
n
6
SD
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
be
tw
ee
n
m
ea
ns
L
og
-l
og
re
gr
es
si
on
on
le
ng
th
of
th
or
ax
Si
gn
ifi
ca
nc
e
of
W
ilk
?s
L
am
bd
a
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
sl
op
es
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
el
ev
at
io
ns
Sl
op
e
Si
gn
ifi
ca
nc
e
of
sl
op
e
In
te
rc
ep
t
le
ng
th
tib
ia
II
I
m
al
e
1.
38
6
.0
5
0.
68
**
**

0.
14
fe
m
al
e
1.
38
6
.0
7
ns
0.
54
**

0.
09
*
ns
*
d.
N
eo
ce
ra
tit
is
cy
an
es
ce
ns
(N
?
27
?3
0
fo
r
fe
m
al
es
,
24
?3
0
fo
r
m
al
es
)
le
ng
th
th
or
ax
m
al
e
1.
76
6
.5
1
fe
m
al
e
1.
99
6
.2
6
ns
w
id
th
he
ad
m
al
e
1.
66
6
.1
3
0.
98
**
**
1.
60
fe
m
al
e
1.
45
6
.6
2
ns
0.
98
**
**
1.
53
*
ns
**
le
ng
th
ar
is
ta
m
al
e
0.
93
6
.0
7
0.
89
**
**

0.
24
fe
m
al
e
0.
95
6
.1
2
ns
0.
82
**
**

0.
26
ns
ns
ns
nu
m
be
r
do
rs
al
se
ta
e
ar
is
ta
m
al
e
37
.6
7
6
4.
37
0.
30
ns
1.
47
fe
m
al
e
36
.9
7
6
6.
85
ns
0.
84
**
**
1.
21
*
**
*
nu
m
be
r
ve
nt
ra
l
se
ta
e
ar
is
ta
m
al
e
25
.7
0
6
3.
34
0.
34
ns
1.
27
fe
m
al
e
26
.5
6
4.
83
ns
0.
77
**
**
1.
09
ns
ns
ns
le
ng
th
w
in
g
m
al
e
3.
30
6
.2
5
0.
78
**
**
0.
33
fe
m
al
e
3.
45
6
.3
9
*
0.
94
**
**
0.
30
ns
ns
ns
w
id
th
w
in
g
m
al
e
1.
75
6
.1
4
0.
77
**
**
0.
06
fe
m
al
e
1.
83
6
.2
2
ns
0.
94
**
**
0.
01
ns
ns
ns
po
st
er
io
r
ar
ea
w
in
g
m
al
e
1.
12
6
.2
6
0.
77
**
**

0.
34
fe
m
al
e
1.
30
6
.2
8
*
0.
95
**
**

0.
35
*
ns
ns
to
ta
l
ar
ea
w
in
g
m
al
e
2.
80
6
.4
0
0.
80
**
**
0.
08
fe
m
al
e
3.
07
6
.6
7
*
0.
95
**
**
0.
00
2
*
le
ng
th
fe
m
ur
I
m
al
e
1.
11
6
.0
9
0.
87
**
**

0.
18
fe
m
al
e
1.
08
6
.1
3
ns
0.
93
**
**

0.
23
**
**
ns
**
le
ng
th
se
ta
fe
m
ur
I
m
al
e
0.
30
6
.0
3
0.
59
**

0.
73
fe
m
al
e
0.
34
6
.0
4
*
0.
84
**
**

0.
73
**
ns
**
ar
ea
se
ta
e
ve
nt
ra
l
fe
m
ur
I
m
al
e
21
50
6
49
0
0.
79
**
**
2.
75
fe
m
al
e
22
40
6
56
0
ns
0.
89
**
**
2.
77
ns
ns
ns
nu
m
be
r
se
ta
fe
m
ur
I
m
al
e
9.
79
6
1.
22
0.
37
ns
0.
83
fe
m
al
e
9.
37
6
1.
21
ns
0.
63
**
**
0.
78
*
ns
*
VOLUME 78, ISSUE 1 29
T
ab
le
2.
C
on
tin
ue
d.
M
ea
n
6
SD
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
be
tw
ee
n
m
ea
ns
L
og
-l
og
re
gr
es
si
on
on
le
ng
th
of
th
or
ax
Si
gn
ifi
ca
nc
e
of
W
ilk
?s
L
am
bd
a
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
sl
op
es
Si
gn
ifi
ca
nc
e
of
di
ff
er
en
ce
s
be
tw
ee
n
el
ev
at
io
ns
Sl
op
e
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30 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY
Similarly, in the two species in which males performed intermittent wing buzzing while
facing females at close range, the male?s wing was wider than that of the female, due to an
expansion of the posterior wing area. The details of wing movements in C. capitata
indicate that the male uses the posterior area of his wing to waft pheromones toward the
female (Bricen?o and Eberhard, 2000), and presumably the same occurs in C. catoirii.
Wing width was not sexually dimorphic in C. rosa and N. cyanescens, in which males did
not buzz their wings this way at close range. The greater similarity between C. capitata
and C. catoirii is in accord with recent taxonomic studies: these two species are in the
same clade within the subgenus Ceratitis s.s., while C. rosa is in a different subgenus
which is not closely related (DeMeyer, 2000). The biological significance of the sexual
differences in the size of wing markings in C. rosa is less clear. Perhaps visual stimuli
from the wings are used in courtship.
The absolute values of the allometric slopes of several display traits (aristae, head bristles,
and posterior wing area in C. capitata and C. catoirii, middle tibiae and their brushes of setae
in C. rosa) were all well below 1.0 (Tables 2a?c), in contrast to the theoretical predictions
discussed above (Otte and Stayman, 1979; Baker and Wilkinson, 2001). Perhaps emphasis
on the value 1.0 in previous discussions of allometry and sexual selection was not justified
(Eberhard, 2002; Bonduriansky and Day, 2003). Simple utilitarian arguments may explain
why some of these traits have relatively low slopes. For instance, an overly long male arista
might bring the male into contact with the female?s aristae before he was close enough to
launch an effective jump. A similar argument based on mechanical design is not applicable,
Table 3. Summary of statistically significant differences between males and females of the four species of
Ceratitis and Neoceratitis (????? ? male values higher than those of similarly sized females, from inspection of
graphs; ??el??? significant difference in elevation; ??sl??? significant difference in slope) (****?P 
 0.0001; ***
? P 
 0.001; ** ? P 
 0.01; * ? P 
 0.05).
C. capitata C. catoirii C. rosa N. cyanescens
width head NO NO NO * (? el)
length arista **** (?, el) **** (?, el) NO NO
number dorsal setae arista **** (, el) **** (, el) NO * (, sl, el)
number ventral setae arista **** (, el) **** (, el) NO NO
length wing * (?, el) *** (, sl, ?, el)a NO NO
width wing **** (?, el) **** (?, sl, el) NO NO
posterior area wing **** (?, el) **** (?, sl, el) NO NOb
total area wing **** (?, el) **** (?, el) NO NOc
area wing bands DB ? SAB NO NO **** (, el) ?
length femur I ** (?, el) **** (?, el) **** (?, el) **** (?, el)
length seta femur I **** (?, el) **** (?, el) * (, el) ** (, el)
area seta femur I * (?, el) **** (?, el) ** (, el) NO
number seta femur I * (?, el) **** (?, el) NO * (?, el)
length tibia I **** (?, sl, el) **** (?, el) **** (?, el) **** (?, el)
length femur II **** (?, el) **** (?, el) **** (?, el) **** (?, el)
length tibia II **** (?, el) **** (?, el) **** (?, el) **** (?, el)
length femur III *** (?, el) NO **** (?, el) ** (?, el)
length tibia III NO ** (?, el) * (?, el) * (?, el)
a Male slope not statistically significant.
b Wilk?s lambda barely significant (P ? 0.03), but neither slope nor elevation significantly different
(respectively, P? 0.70, 0.09).
c Wilk?s lambda barely significant (P ? 0.03), but neither slope nor elevation significantly different
(respectively, P? 0.14, 0.72).
VOLUME 78, ISSUE 1 31
however, for the SFO setae of C. capitata and C. catoirii, or the brush of setae on tibia II of
C. rosa. The reduced frequency of female acceptance during courtship in C. capitata when
the SFO setae were removed (Mendez et al., 1998), and the sharp difference between the
sizes and colors of SFO setae in C. capitata and C. catoirii, suggests that they may be under
sexual selection; nevertheless their allometric slopes were especially low, and were not even
statistically significant in three of four measures. The sizes of the SFO setae are thus poor
indicators of male size, and seem more likely to have evolved under female choice for
??arbitrary?? traits rather than as indicators of male size. There are further sexual dimorphisms
in some of these species (greater pilosity on the front femur of males of C. capitata and
C. catoirii, larger frontal bristles in male C. catoirii): evaluation of their possible
significance (e.g., visual stimuli, dispersers of chemical stimuli, threats during male-male
interactions) must await further behavioral studies.
Most sexual dimorphisms resulted from male-female differences in elevation (N ? 52
cases) rather than slope (N? 5 cases). Perhaps changes of elevation require less reorgani-
zation of developmental programs than do changes in slope, and are thus easier to evolve.
Acknowledgments
RDB and WGE thank Eddy Camacho for technical help, Bernal Burgos and Hernan
Camacho for specimens of wild Costa Rican flies, Jorge Lobo and Federico Bolan?os for
help with statistics, and the International Atomic Energy Agency, the Smithsonian
Tropical Research Institute, and the Vicerrector??a of the Universidad de Costa Rica for
financial support.
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