BEHAVIOR
The Natural History and Unusual Mating Behavior of Euxesta bilimeki
(Diptera: Ulidiidae)
ODETTE BRUNEL1
AND
JUAN RULL2
Ann. Entomol. Soc. Am. 103(1): 111Ð119 (2010)
ABSTRACT We report results of a 2-yr study aimed at describing the natural history and mating
behavior of Euxesta bilimeki (Hendel) (Diptera: Ulidiidae) a picture-winged ßy species associated
with Agave atrovirens Karw. ex Salm-Dyck (Agavaceae) in the Mexican altiplano. The study consisted
of direct Þeld observations and a year-long population survey in the Þeld complemented with
laboratory experiments and observations. E. bilimeki was found to be multivoltine, able to resist
temperatures below freezing during winter, and it developed on rotting agave leaves in large larvalÐ
pupal aggregations. Adults fed on carbohydrate and protein sources found on the plant, where they
could be sighted all year long. Courtship was based on a sequence of visual and tactile displays that
could result in female rejection of courting males. Males constantly harassed females, who mated
multiple times, but frequently expelled and consumed ejaculates after mating. We discuss hypotheses
on the evolution of this rare behavior and highlight the value of performing descriptive studies on the
natural history of poorly known taxonomic groups to foster understanding of the evolution of behavior.
KEY WORDS Ulidiidae, natural history, ejaculate expulsion
Picture-winged ßies (Diptera: Ulidiidae) belong to a
little studied family within the superfamily Tephritoidea (McAlpine 1989, Korneyev 2000). The few ulidiid species that have been observed in nature exhibit
elaborate courtship behaviors (Allen and Foote 1967,
1975; Alcock and Pyle 1979; Yoon et al. 1983; Seal and
Jansson 1989; Sivinski 2000).
There are ⬇800 described species of Ulidiidae
(Dṍaz-Fleischer et al. 2000), most of which are generalist saprophages (Allen and Foote 1992), with some
species tending to phytophagy (Dṍaz-Fleisher et al.
2000). Knowledge on basic biology and behavior for
this group is scant and mostly limited to a handful
of species, most of them of economic importance
(Harper 1962; Allen and Foote 1967, 1975; Frṍas 1978;
Martos-Tupes 1982; Yoon et al. 1983; Seal and Jansson
1993; Seal et al. 1995).
In contrast to Ulidiidae, true fruit ßies (Diptera:
Tephritidae) have been extensively studied on account of their economic importance (Dṍaz-Fleischer
and Aluja 2000). The wealth and diversity of sexual
behaviors of Tephritidae makes such organisms ideal
subjects to illuminate the evolution of mate choice and
sexual competition (Sivinski et al. 2000). This fact has
fostered numerous studies on sexual behavior of these
insects (reviewed in Sivinski et al. 2000), and some
theoretical efforts to understand the evolution of their
1
Instituto de Neuroetologṍa, Universidad Veracruzana, Apartado
postal 566, Xalapa, Ver., 91000, Mexico.
2 Corresponding author: Instituto de Ecologia, A.C., Km 2.5 Carretera
Antigua Carretera a Coatepec No. 257, Congregación El Haya, C.P. 91070
Xalapa, Veracruz, Mexico (e-mail: [email protected]).
mating systems (Prokopy 1980, Burk 1981, Headrick
and Goeden 1994).
Understanding the evolution of tephritid behavior
would beneÞt from larger data sets created by the
inclusion of nontephritid tephritoids to allow identiÞcation of convergent evolutionary patterns and their
ecological correlates by means of comparative studies
(Sivinski 2000).
Two species of Ulidiidae have been reported in
association with Agave atrovirens Karw. ex Salm-Dyck
(Agavaceae) in the Mexican altiplano, Pseudodyscrasys scutellaris (Wiedemann) (Diptera Ulidiidae), and
Euxesta bilimeki (Hendel) (Diptera Ulidiidae) (Hernández-Ortiz 1999). Both species are sympatric in
Veracruz and little is known about them other than
their taxonomic status (Hernández-Ortiz 1988) and
their association with agaves (Hernández-Ortiz 1999).
Recently, the natural history and mating behavior
of P. scutellaris were described (our unpublished
data). Here, we report results of a 2-yr study aimed
at describing the natural history and mating behavior of E. bilimeki, a species that displays unusual
sexual behavior. This study was undertaken as a Þrst
step toward understanding the mating system of this
species.
Materials and Methods
Study Site. Field work was performed in the Mexican highlands near the locality of Cerro del León,
municipality of Perote, Veracruz, on the PeroteTeziutlán road (19⬚ 33⬘ 36⬙ N; 97⬚ 14⬘ 03⬙ W) at an
elevation of 2,463 m, with mean annual precipitation
0013-8746/10/0111Ð0119$04.00/0 䉷 2010 Entomological Society of America
112
ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA
of 445.3 mm and an average temperature of 12⬚C,
(min., ⫺10.0⬚C; max, 33.5⬚C). The site is composed of
a series of 0.25- to 2-ha agricultural Þelds, typically
planted with corn, Zea mays L.; broad beans (Vicia
spp.); pastures; or left fallow. These Þelds are bordered by compact rows of A. atrovirens serving as
hedges, with plants separated by 0.3Ð1 m. A. atrovirens
is native to central Mexico and has been cultivated in
this manner in the Altiplano since the twelfth century
(Gentry 1982). Observations and experiments in the
laboratory were performed at the Instituto de Ecologṍa A.C. in Xalapa, Veracruz, under environmentally
controlled conditions (24⬚C, 65% RH, and a photoperiod of 12:12 [L:D] h).
Population Surveys. The Þrst A. atrovirens at the
Eastern edge of an eastÐwest 200-plant row was selected and conspicuously carved with the tip of a knife
on the underside of an outer leaf with a 30-cm-high
number 1. The following plant was selected by walking
down the line toward the west and counting 10 plants
and marked with number 10. In total, 10 plants were
selected and numbered from 1 to 90 in intervals of 10
(1, 10, 20, 30, 40, 50, 60, 70, 80, and 90). At the end of
each month, all adults on every numbered plant were
captured during the morning and placed in 200-ml
plastic vials in a 70% ethyl alcohol solution. The number and sex of captured ßies were recorded later in the
laboratory at Xalapa. All leaves of each numbered
plant were visually inspected and where damage
marks were found (necrotic, discolored, dry, or otherwise damaged plant tissue), they were opened
with a knife in search of larvae. Because larvae and
pupae were found on complete rotting agave leaves
which were rare, overall three of those infested
leaves were taken to the laboratory and placed in
closed 30- by 30- by 60-cm Plexiglas cages under
controlled conditions (24⬚C, 65% RH, and a photoperiod of 12:12 [L:D] h) to allow adult emergence.
All adults emerging from rotting leaves were then
counted.
Also, ⬇2 kg of the upper layer (2Ð5 cm) of soil
around the base of each of the 10 numbered plants
were sieved each month through a 1-mm wire mesh in
an attempt to recover pupae buried in the soil. The
survey was performed for a full year from January to
December 2006.
Age of Sexual Maturity. To determine the age at
sexual maturity, E. bilimeki pupae were obtained from
a Þeld of infested agave leaves and taken to the laboratory at Xalapa. At emergence adults were placed in
13- by 13- by 25-cm plastic cages with free access to
water and food consisting of Þlter paper strips soaked
in a slurry paste made with three parts of sucrose
(Baker Analyzed R) and one part of protein (Yeast
Hydrolysate Enzymatic, ICN Biomedicals, Irvine, CA).
Five recently emerged, 5-d-old, 10-d-old, and 15-dold males and females were placed in a 99.9% solution of ethyl acetate (J.T. Baker, Mallinckrodt Baker
Inc., Phillipsburg, NJ) and dissected under a stereoscope (SMZ 1500, Nikon, Tokyo, Japan) to observe gonadal development. Females with one or
more mature eggs in their ovarioles, and males with
Vol. 103, no. 1
fully developed testes (large and rounded structures occupying more than half of the abdominal
cavity) were considered as mature.
Size of Male Gonads. During dissections of male
genitalia to determine age at sexual maturity, male
testes were found to be extraordinarily large. Twenty
male E. bilimeki and 20 males of a sympatric species
of Ulidiidae, P. scutellaris were dissected under an
SMZ 1500 microscope, with a 2Ð1.6⫻. lens, equipped
with a camera and connected to a computer. With
aid of NIS-ELEMENTS AR 2.20 software the size of
the intact abdomen and dissected gonads was measured and the percent space occupied by gonads in
the abdomen was estimated for both species.
Longevity. To estimate average adult life span, E.
bilimeki pupae were obtained from the Þeld and taken
to the laboratory. At emergence, adults were placed in
Plexiglas 30- by 30- by 30-cm cages with free access to
water and food. Mortality was recorded daily until the
death of the last adult in cages and mean age of death
was determined.
Behavioral Observations. Field Observations. Field
observations were done during summer and fall 2007
around the peak of adult abundance (July, August,
September, and October). In total, 144 h of observation in 12 periods were accumulated. Based on studies
by Aluja and Birke (1993), continuous 12-h observation periods were performed from dawn to dusk to
record ßy activity. A focal individual was selected at
random from a different plant and different sex each
time. The focal individual was captured early in the
morning when low temperatures (⬇ⱕ10⬚C) reduced
general activity, and gently marked on the back of the
thorax with a distinctive dot of paint (Politec, Distribuidora Rodṍn S.A. de C.V., Distrito Federal, México).
Once marked the adult was gently placed back on the
surface of the plant.
Each behavior and its hour of occurrence was recorded. Every hour, temperature and relative humidity were recorded with a hygrothemographer placed
in the shade under a leaf of the agave. In addition to
focal individual behavior, all predation events within
visual range of the observer during observations on the
focal plant were recorded.
The following categories of events were recorded in
a continuous manner: feeding (including sources);
interspeciÞc interactions (including predation); oviposition; and intraspeciÞc interactions, with any maleÐ
male and maleÐfemale displays being recorded. During analysis, the total number of displays in each
category was summed.
Wing displays were classiÞed according to Headrick
and Goeden (1994) as follows: Enantion: Simultaneous extension of both wings at the same time in the
same direction, toward the front (head) in parallel to
the substrate (horizontally). Hamation: Simultaneous
movement of both wings in parallel to the substrate in
opposing direction from one another. Bubbling:
Adults regurgitating a droplet of liquid which is maintained in exposure to elements at the tip of the proboscis presumably to concentrate sugars through water evaporation (Hendrichs et al. 1992).
BRUNEL AND RULL: NATURAL HISTORY AND BEHAVIOR OF E. bilimeki
Average ( ±s.e) of adults per plant
(n= 10) per month
January 2010
35
113
a
30
25
abc
15
10
abc
abc
abc
20
bc
abc
ab
abc
abc
abc
c
5
0
1
2
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Month of the year
* Bars with the same letters are not significantly different from each other
(P<0.05; ANOVA followed by Tukey HSD test)
Fig. 1. Average (⫾SD) number of adult E. bilimeki per A. atrovirens collected per plant (N ⫽ 10) per month during 2006.
Monthly capture of adults was compared among plants by means of an ANOVA followed by TukeyÕs HSD test.
Laboratory Observations. Because courtship and
mating behavior of E. bilimeki was observed to be
extremely brief, it was difÞcult to determine in the
Þeld whether effective intromission occurred during
mounting. To describe the complete courtship sequence leading to successful intromission, sexually
mature (15-d-old) couples (N ⫽ 30) obtained as pupae
from Þeld infested rotting agave leaves were introduced into a small rectangular glass cage made with
four 76- by 26- by 76-mm microscope slides glued
together. Flies were released into these small cages
and closely observed for 1 h. During this period, based
on the sequence of events observed in the Þeld, every
display in order of occurrence was recorded in a format. At the end of observations, all sequences were
summed, and the courtship and mating sequence was
established.
Statistical Analysis. The number of adults collected
per month per plant (N ⫽ 10) was compared by
means of a Generalized Linear Model followed by
analysis of variance (ANOVA) and TukeyÕs honestly
signiÞcant difference (HSD) comparison of means
test. The observed proportion of the total captures
per plant (N ⫽ 12) was compared with an expected
uniform distribution of adults per plant by means of
a chi-square test. Daily sexual activity patterns were
analyzed by comparing the frequency of observed
mountings across the hour of day versus an expected
even distribution of total events with a chi-square
test. The effect of temperature on ßy activity for 12
independent observation periods was analyzed by
means of a second order regression of total number
of recorded events (intraspeciÞc wing displays, and
copulation attempts) per temperature category.
The percentage of space occupied by male testes in
the abdominal cavity was compared between E.
bilimeki and P. scutellaris by means of a t-test for
independent samples using STATISTICA 7 (StatSoft, Tulsa, OK).
Results
Life History. Adults of E. bilimeki were recovered
from agave plants all year-round (Fig. 1) (H11, 120 ⫽
33.82; P ⫽ 0.0004), with a decrease in abundance
during winter. The adult sex ratio per plant (males per
female) across the season was not signiÞcantly different from 1 (␹2 ⫽ 4.82, df ⫽ 9, P ⫽ 0.84) and averaged
1.51 ⫾ 0.46 (mean ⫾ SD). The adult population peak
was recorded during August. Adults of E. bilimeki in
the laboratory lived an average of 64.29 ⫾ 22.3 d (N ⫽
74). Sexual maturity was reached by 40% of females
and 0% of males by day 5, by day 10 100% of females
and 60% of males were mature, and by day 15 all
dissected adults were mature.
Detection of large aggregations of larvae and pupae
was erratic (both because very few leaves were found
to be infested and because they were found at different times of the year). They were found in rotting
agave leaves in May, October, and November. Three
infested agave leaves taken to the laboratory yielded
an average of 307 ⫾ 222.81 (mean ⫾ SE) adults per
leaf. In contrast to other species of Tephritoidea, E.
bilimeki larvae did not leap and pupated within the
plant tissue close to the leaf surface. As a consequence,
no pupae were found buried in the soil.
E. bilimeki seemed to be multivoltine. It was able to
resist temperatures below 0⬚C during winter and to
infest rotting agave leaves whenever the opportunity
arose.
Some plants accumulated a greater proportion of
the total capture of adults than others (Fig. 2) (␹2 ⫽
46.27, df ⫽ 9, P ⬍ 0.0001). Such plants may have
attracted or arrested a greater number of adults from
the population. Attractive plants seemed to show a
greater degree of herbivore damage.
Behaviors. Feeding. Forty events associated with
feeding were recorded for E. bilimeki adults (both
focal ßies and other). Males and females were recorded extending their proboscis and contacting wa-
ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA
Average number of adults (+s.d) captured
over the year (n= 12) per plant
114
Vol. 103, no. 1
25
*
20
*
15
10
*
5
0
1
10
20
30
40 50
Plant number
60
70
80
90
(X2 = 46.27 df = 9 p < .0001) * frequencies
above expected uniform distribution of adults
Fig. 2. Average (⫾SD) number of adult E. bilimeki collected per month (N ⫽ 12) on each of 10 A. atrovirens plants during
2006. Frequencies above a uniform distribution of ßies per plant were compared by means of a chi-square test. Averages
(⫾SD) are shown to ease interpretation.
ter on the leaf surface deposited by rain and dew (four
events), both sexes also were observed bubbling
(three events), and both sexes were observed consuming protein (faeces, dead arthropods, and rotting
agave tissue) and carbohydrate (leaf leachates, plant
sap) sources. Food sources and frequency of feeding
events are shown in Table 1. It was not always possible
to determine the sex of ßies during feeding (only lateral
views of females where the ovipositor was apparent to
the observer) and therefore no detailed analysis of
feeding according to sex could be accurately done.
Interspecific Interactions. Sixty six interspeciÞc interactions were witnessed during observations, the
majority with adults of both sexes of another ulidiid,
P. scutellaris (68.2%), followed by encounters with
ants (16.7%), other dipterans (13.6%) and predators
(1.5%). In all cases, independently of the aggressor,
ßies engaged in frontal wing waving (enantion and
hamation) occasionally followed by head butts and
chasing. During population sampling, on nine occasions, remains of E. bilimeki (wings) were found in
Table 1. Source and number of feeding events recorded during
behavioral observations of E. bilimeki adults
Source
Live agave
tissue
Description
Intact leaf surface (grazing)
Fresh sap dripping from lepidopteran
larvae feeding scars on the rosette
Fresh sap dripping from cracks
between thorns on leaves
Rotting agave
Dark liquid secretions from necrotic
agave leaves (typically at the base
of the plant)
Secretions from brown dry spots
(frost damage or disease) on the
underside of leaves
Dry lepidopteran larvae feeding scars
External sources Bird and lizard faeces
Dead arthropods
Total no.
events
4
8
2
3
spider webs plastered on the leaf surface between the
rosette and opening young agave leaves where ßies
frequently entered to feed on sap exudating from
Lepidoptera feeding scars. On two occasions remains
were found in funnels built by a spider within the
rosette, and on one occasion a salticid spider was
observed capturing a ßy. Frequency and nature of
encounters during behavioral observations is described in Table 2.
Ovipositon. No oviposition events were witnessed
during observations. In contrast to a sympatric species
of Ulidiidae (P. scutellaris) (our unpublished data) no
larvae or pupae were found on any of the 10 plants
surveyed monthly over the year. Extended sampling of
unmarked plants on the 200-plant Agave line described in Materials and Methods revealed that larvae
and pupae could be found in rotten agave leaves that
were dark black and very moist. Infested leaves were
found during spring, fall, and winter, suggesting a lack
of seasonality in larval development. Such Þndings
seem to suggest that E. bilimeki oviposits when the
opportunity arises and females are able to Þnd rotting
leaves of these particular characteristics.
Intraspecific Interactions. MaleÐFemale. Male E.
bilimeki continuously patrolled A. atrovirens and
seemed to harass females that were resting, walking, or
Table 2. Participants, description and frequency of interspecific interactions during field observations of E. bilimeki
Interaction
with
P.scutellaris
6
Ants
2
7
1
Other Diptera
Predators
Description
Frequency
Wing displays (enantion, hamation)
occasionally followed by head
butts and chases
Tending Lepidoptera feeding on
rosette
Conßicts around food sources
Weaving spiders
45
11
9
1
January 2010
BRUNEL AND RULL: NATURAL HISTORY AND BEHAVIOR OF E. bilimeki
115
♂ faces ♀ and performs enantion wing
displays (542/542).
♀ Retires, ♂ tends to
pursue (211/542).
♀ Extends aculeus but places
it in contact with surface
preventing intromission,
retires, or ♂ fails to achieve
intromission (189/542).
38.9%
♂ Takes position behind ♀, taps the back of
the abdomen with front legs while extending
proboscis, ♀ responds with enantion wing
displays. (331/542).
34.9%
26.2%
♀ Lifts ovipositor sheath and fully
extracts aculeus, ♂ introduces aedagus
while performing hamation displays
(142/542).
9.9%
♂ Achieves intromission and
♀ Withdraws
without expelling
drop (27/542).
♀ Withdraws without
consuming drop
(5/542).
4.9%
pushes until retracting the
aculeus into ♀ ovipositor
sheath (54/542).
4.9%
Couple separates, ♀ lifts ovipositor, extracts
aculeus, cleans with hind legs and deposits a
drop on the substrate (27/542).
0.9%
4%
♀ turns in 180° angle extiends
proboscis and consumes
expelled drop (22/542).
Fig. 3. Description, frequency, and percentage of sequential behavioral displays per 1-h laboratory observational periods
for 30 E. bilimeki sexually mature couples.
feeding by chasing them, performing frontal wing displays at close range, followed by abdominal tapping.
On 15 occasions, the male failing to obtain response
from a female after drumming the abdomen seemed to
prevent the female from escaping by moving in front
of her and contacting the femaleÕs face with the tip of
his abdomen. After such a display the male usually
resumed abdominal tapping. On 33 occasions, more
than one male (up to three) took position close to a
female (1Ð2 cm), in line or in parallel, taking turns to
court the female (tapping her abdomen) and chasing
her when she attempted to escape, for periods of time
that could surpass the hour. In total, 99 male female
interactions were recorded, including 58 mountings
and 41 courtship displays that did not culminate in
mounting.
MaleÐMale. Male-male interactions were not as frequent (N ⫽ 24) or elaborate as male-female interactions (N ⫽ 99) and consisted simply of rapid wing
movements of enantion and hamation, occasional
head butts, lateral kicks, and chases.
Courtship and Mating Sequence. Observation of 30
E. bilimeki couples for 1-h periods in the laboratory
resulted in the recording of 542 sequences. All sequences Þnishing in copulations were preceded by a
series of displays in the following order: frontal male
wing displays (enantion), male positioning behind
female, vigorous tapping of the female abdomen with
both front legs and extension of the proboscis, the
female lifts its ovipositor and fully extends the aculeus
out of the ovipositor sheath, intromission, male pushes
the extended aculeus until achieving full retraction
into the ovipositor sheath and the couple separates
(Fig. 3).
After separation, the female frequently cleaned its
ovipositor with its hind legs, fully extended the aculeus, rapidly deposited a droplet of liquid, turned in
a 180⬚ angle, and consumed the drop. Occasionally, the
female expelled and consumed the drop minutes after
copulation away from the male. Out of 54 courtship
sequences resulting in effective intromission, on 27
occasions (50% of the time) females expelled a drop,
and having expelled it on 22 occasions (82%) they
consumed the drop. Observation of droplets under the
microscope revealed that droplets contained spermatozoids.
Under laboratory conditions, females could mate
and consume sperm up to three times within an h of
observation (one female expelled sperm three times,
six females twice, 11 once, and 12 none).
Daily Activity Patterns in the Field. Copulation
attempts were spread over the day with a slight bimodal tendency. A chi-square test revealed no significant differences between observed and expected frequencies (␹2 ⫽ 11.93, df ⫽ 11, P ⫽ 0.368) over time,
with slight decreases in frequency early in the morning, around midday during the hottest period of the
day, and at the end of the day (Fig. 4).
ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA
Total number of mountings observed
116
Vol. 103, no. 1
10
9
8
7
6
5
4
3
2
1
0
8:00
9:00
10:00
11:00 12:00 13:00 14:00
15:00 16:00
17:00 18:00
Time of day
(X2 = 11.93 df = 11 p < .368)
Fig. 4. Total number of copulation attempts observed for E. bilimeki for 144 h over 3 mo, by time of day (hours).
Frequencies above a uniform distribution of copulations per time of day (hours) were compared by means of a chi-square
test.
Total number of mounting attempts at different
temperatures on 12 independent plants.
Temperature and Activity. Adult activity was inßuenced by temperature, ßies were less active at both low
and high temperatures. At dawn, with temperatures below 10⬚C, ßies were found motionless resting on the
agave clustered around the rosette. At dusk, ßies gradually reduced activity and adopted positions similar to
those in which they were found at dawn. During warm
periods at midday, when temperatures could reach 30⬚C,
ßies tended to reduce activity and Þnd shaded locations
on the plant. A second order polynomial regression between temperature and activity (mounting) revealed a
signiÞcant relationship between activity and temperature (R2 ⫽ 0.32; P ⫽ 0.043) (Fig. 5).
Size of Male Testes. Male testes occupied a significantly greater proportion of the abdominal cavity for
E. bilimiki (72.79 ⫾ 12.86%) than for sympatric P.
scutellaris (18.8 ⫾ 6.03%) males (t-test: t1, 38 ⫽ 17.02;
P ⬍ 0.001; N ⫽ 20).
Discussion
E. bilimeki was found year-round feeding, mating,
and developing on agave plants. Adults lived for ⬎2
mo in the laboratory, which suggests that this species
is multivoltine and able to resist temperatures below
freezing without diapausing during winter. E. bilimeki
was found to be a plant saprophage, developing and
pupating in rotten agave leaves of particular conditions that were found erratically over the year. Adults
exhibited an elaborate mating behavior with courtship
14
12
y = -0.0667x 2 + 2.3611x - 14.224
R2 = 0.3237
10
8
6
4
2
0
0
5
10
15
20
25
30
Temperature in º C
Fig. 5. Total number of E. bilimeki copulation attempts for 144 h of observation, over 3 mo, by temperature (⬚C). The
relationship between temperature and occurrence of mounting attempts was determined by means of a second-order
polynomial regression.
January 2010
BRUNEL AND RULL: NATURAL HISTORY AND BEHAVIOR OF E. bilimeki
based on short distance visual displays and physical
stimulation. Females were constantly harassed, mated
multiple times, and frequently expelled and consumed
sperm transferred during copulations.
Adult feeding behavior of E. bilimeki was very similar to that of several species of Tephritidae and a
recently studied species of Ulidiidae (our unpublished
data). E. bilimeki adults of both sexes fed on carbohydrate and protein sources. Carbohydrates are
thought to fuel metabolic activity, and sources of protein are required for gonadal development (Drew and
Yuval 2000). This saprophagous species of Uliididae
matured sexually ⬇15 d after emergence and can
therefore be considered as anautogenous. Bubbling,
another behavioral pattern observed among E. bilimeki
adults, also has been reported for another species of
Ulidiidae (our unpublished data) and several tephritids (Drew and Yuval 2000). Bubbling consists in regurgitating a droplet of water and dissolved nutrients
after feeding (Hendrichs et al. 1992), a behavior that
allows water evaporation and nutrient concentration.
With respect to mating behavior, E. bilimeki males
were not observed calling or extending pleural or anal
glands, but they were observed performing several
kinds of wing displays and physical stimulation of
females by males in the form of abdominal tapping in
a sequential order suggestive of courtship. Males were
not found defending territories or engaging in agonistic encounters and constantly harassed females. Females could apparently reject courtship if failing to
extrude the aculeus after abdominal tapping by males,
a behavior also reported during mating for Euxesta
sororcula (Wiedemann) (Diptera:Ulidiidae) in Peru
(Martos-Tupes 1982); however, this most frequently
resulted in males persistently resuming courtship,
mounting attempts, and chases that were probably
costly for both sexes in terms of energy expenditure.
Although in insects, nuptial gifts have been found to
take the form of food captured by the male, parts or
the whole of the maleÕs body, glandular products such
as salivary secretions, external glandular secretions,
spermatophores, and substances in the ejaculate (Vahed 1998), ejaculate expulsion and consumption is a
rare behavior and has only been reported for a few
species of Empididae and Piophilidae (Hamm 1933,
Bonduriansky and Brooks 1998, Preston-Mafham 1999,
Bonduriansky 2003, Bonduriansky et al. 2005).
Several questions arise to explain this behavior.
During sperm expulsion and consumption, female E.
bilimeki could be expelling part of each maleÕs ejaculate to be able to retain some sperm from several
males to derive genetic beneÞts from multiple copulations, or to exploit postcopulatory mechanisms to
minimize the risk/cost of fertilization by genetically
incompatible sperm (Newcomer et al. 1999). If this is
true, females mating multiple times with different
males should exhibit higher fecundity and fertility
than females mating singly and females mating multiple times with a single male.
An alternative explanation could be that females
engage in more copulations than those necessary, to
achieve maximum fertility and avoid energy expendi-
117
ture during male rejection (Sivinski et al. 2000). After
each copula females may expel the sperm of some
males and retain sperm from others as a form of cryptic
female choice (Eberhard 1991). Manipulation of male
traits known to inßuence female choice in some tephritoid species, such as size, nutritional condition,
and experience (Perez-Staples et al. 2008), could shed
some light in verifying this hypothesis.
Alternatively, if egg-laying opportunities are unpredictable and rare, females may continuously mate over
their lifetime and retain sperm only when oviposition
sites (rotting agave leaves in suitable condition) are
available. In the mean time, E. bilimeki females could
derive nutritional beneÞts from sperm consumption
which could translate in greater longevity or ovarian
development.
Ejaculate consumption in Piophilidae has been interpreted as an early stage in the evolution of nuptial
gifts (Bonduriansky and Brooks 1998, Bonduriansky et
al. 2005) as it increases female egg-laying propensity
without detriment to longevity. However, piophilid
females that expel sperm do not seem to mate multiple
times, suggesting that male ejaculates may contain
substances causing remating inhibition. According to
Bonduriansky et al. (2005), if ejaculates consumed by
piophilid ßies were just a benign gift conferring cumulative beneÞts, females should forage for multiple
matings. Whether this is the case for E. bilimeki, which
was found to engage in multiple copulations, remains
to be investigated. Although we have no current
knowledge on the effect of sperm feeding on female
Þtness, our behavioral observations indicate that it is
rather males that forage for females.
Regardless of the factors that have favored the evolution of sperm expulsion and consumption in E.
bilimeki, this behavior seems to have selected for extraordinarily large male testes compared with P. scutellaris, which does not present this behavior. It has been
proposed that gonad size is correlated with sperm
competition and multiple mating (Stockley et al. 1997).
For E. bilimeki, large male testis size also could be the
result of selection by multiple mating and sperm competition; however, female ejaculate expulsion and
consumption behavior per se could be having an effect
on male testis size evolution. It would be interesting to
compare testes size between species of Piophilidae
that mate singly but expel sperm and closely related
species that do not expel sperm to asses unequivocally
the effect of female behavior on male testes size.
Understanding the evolution of E. bilimeki mating
behavior will require laboratory experiments where
both females and males can be manipulated. Fortunately, E. bilimeki readily performs under conÞned
conditions, and although under such circumstances
females may be forced to mate more often than in the
Þeld, this renders E. bilimeki a good model for studying
maleÐfemale conßict over mating rate. Describing the
natural history and mating behavior of other species in
the genus Euxesta is another avenue for understanding
the inßuence of resource distribution on the evolution
of mating systems for this group. In general, our study
highlights the value of performing descriptive studies
118
ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA
on the natural history of poorly known taxonomic
groups in raising behavioral, ecological, and evolutionary questions.
Acknowledgments
We are grateful to Martṍn Aluja for constructive comments
on design of observations and interpretation of results. We
also thank Jorge Morales, Gustavo Carmona, and Francisco
Garcṍa for suggestions on results interpretation. We thank
Karina Raya, Guadalupe Córdova, Dario Garcṍa, and Erika
Garcṍa for assistance during Þeld observations. We also thank
Gadi V. P. Reddy and three anonymous reviewers for constructive criticism of an early version of the manuscript .O.B.
was a fellow of the Consejo Nacional de Ciencia y Tecnologṍa
(CONACyT 197659) for the duration of this study.
References Cited
Alcock, J., and D. W. Pyle. 1979. The complex courtship of
Physiphora demandata (Diptera: Otitidae). Z. Tierpsychol. 49: 352Ð362.
Allen, E. J., and B. A. Foote. 1967. Biology and immature
stages of three species of Otitidae (Diptera) which have
saprophagous larvae. Ann. Entomol. Soc. Am. 60: 826 Ð
836.
Allen, E. J., and B. A. Foote. 1975. Biology and immature
stages of Tritoxa incurva (Diptera: Otitidae). Proc. Entomol. Soc. Wash. 77: 247Ð257.
Allen, E. J., and B. A. Foote. 1992. Biology and immature
stages of Chaetopsis massyla (Diptera: Otitidae), a secondary invader of herbaceous stems of wetland monocots
Proc. Entomol. Soc. Wash. 94: 320 Ð328.
Aluja, M., and A, Birke. 1993. Habitat use by adults of Anstrepha obliqua (Diptera: Tephritidae) in a mixed mango
and tropical plum orchard. Ann. Entomol. Soc. Am. 86:
799 Ð 812.
Bonduriansky, R. 2003. Layered sexual selection: a comparative analysis of sexual behaviour within an assemblage of
piophilid ßies. Can. J. Zool. 81: 479 Ð 491.
Bonduriansky, R., and R. J. Brooks. 1998. Copulation and
oviposition behaviour of Protopiophila litigata (Diptera:
Piophilidae). Can. Entmol. 130: 399 Ð 405.
Bonduriansky, R., J. Wheeler, and L. Rowe. 2005. Ejaculate
feeding and female Þtness in the sexually dimorphic ßy
Prochyliza xanthostoma (Diptera: Piophilidae). Anim. Behav. 69: 489 Ð 497.
Burk, T. 1981. Signaling and sex in acalyptrate ßies. Fla.
Entomol. 64: 30 Ð 43.
Dı́az-Fleischer F., and M. Aluja. 2000. Behavior of tephritid
ßies: a historical perspective, pp. 39 Ð72. In M. Aluja and
A. L. Norrbom [eds.], Fruit ßies (Tephritidae): phylogeny and evolution of behavior. CRC, Boca Raton, FL.
Dı́az-Fleischer F., D. R. Papaj, R. J. Prokopy, A. L. Norrbom,
and M. Aluja. 2000. Evolution of fruit ßy oviposition
behavior, pp. 811Ð 842. In M. Aluja and A. L. Norrbom
[eds.], Fruit ßies (Tephritidae): phylogeny and evolution
of behavior. CRC, Boca Raton, FL.
Drew, R.A.I., and B. Yuval. 2000. The evolution of fruit fly
feeding behavior, pp. 731–750. In M. Aluja and A. L.
Norrbom [eds.], Fruit ßies (Tephritidae): phylogeny and
evolution of behavior. CRC, Boca Raton, FL.
Eberhard, W. G. 1991. Copulatory courtship and cryptic
female choice in insects. Biol. Rev. 66: 1Ð31.
Frı́as, D. L. 1978. Estudios ecológicos en Euxesta eluta y
Euxesta annonae (Dṍptera: Ottitidae). Agric. Téc. Chile
38: 110 Ð114.
Vol. 103, no. 1
Gentry, H. S. 1982. Agaves of continental North-America.
The University of Arizona Press, Tucson, AZ.
Hamm, A. H. 1933. The epigamic behaviour and courtship
of three species of Empididae. Entomol. Mon. Mag. 69:
113Ð117.
Harper, A. M. 1962. Life history of the sugarbeet root maggot in southern Alberta. Can. Entomol. 94: 1334 Ð1340.
Headrick, D. H., and R. D. Goeden. 1994. Reproductive
behavior of California fruit ßies and the classiÞcation and
evolution of Tephritidae (Diptera) mating systems. Stud.
Dipterol. 1: 194 Ð252.
Hendrichs, J., S. S. Cooley, and R. J. Prokopy. 1992. Post
feeding bubbling behavior in ßuid-feeding Diptera: concentration of crop contents by oral evaporation of excess
water. Physiol. Entomol. 17: 153Ð161.
Hernández-Ortiz, V. 1988. Reconsideración taxonómica del
Género Dyscrasis Aldrich y la descripción de Pseudodyscrasis Gen. Nov. (Diptera: Otitidae). Folia Entomol. Mex.
74: 181Ð188.
Hernández-Ortiz, V. 1999. Catálogo de insectos y ácaros
plaga de los cultivos agrṍcolas de México, pp. 74 Ð75. In
A. C. Deloya López and G.J.E. Valenzuela [eds.], Sociedad Mexicana de Entomologṍa, Publicaciones Especiales No. 1, México.
Korneyev, V. A. 2000. Phylogenetic relationships among the
Families of the Superfamily Tephritoidea, pp. 3Ð22. In M.
Aluja and A. L. Norrbom [eds.], Fruit ßies (Tephritidae):
phylogeny and evolution of behavior. CRC, Boca Raton, FL.
Martos-Tupes, A. 1982. Aspectos de la biologṍa y comportamiento de Euxesta sororcula W. (Diptera-Otitidae)
plaga del maṍz. Rev. Per. Entomol. 25: 55Ð 64.
McAlpine, J. F. 1989. Manual of Neartic Diptera. Monograph 32. Agriculture Canada, Ottawa, ON, Canada.
Newcomer, S. D., J. A. Zeh, and D. W. Zeh. 1999. Genetic
beneÞts enhance the reproductive success of polyandrous
females. Proc. Natl. Acad. Sci. USA 96: 10236Ð10241.
Perez-Staples, D., M. Aluja, R. Macı́as-Ordóñez, and J. Sivinski. 2008. Reproductive trade-offs from mating with a
successful male: the case of the tephritid ßy Anastrepha
obliqua. Behav. Ecol. Sociobiol. 62: 1333Ð1340.
Preston-Mafham, K. G. 1999. Courtship and mating in Empis
(Xanthempis) trigramma Meig., E. tessellata F. and E.
(Polyblepharis) opaca F. (Diptera: Empididae) and the
possible implications of ÔcheatingÕ behaviour. J. Zool. 247:
239 Ð246.
Prokopy, R. J. 1980. Mating behavior of frugivorous Tephritidae in nature, pp. 37Ð 46. In J. Koyama [ed.], Proceedings of a Symposium on Fruit Fly Problems. XVI
Internation Congress of Entomology, 9 Ð12 August 1979,
Kyoto, Japan. National Institute of Agricultural Science
Yatabe, Ibaraki, Japan.
Seal, D. R., and R. K. Jansson. 1989. Biology and management of corn silk ßy, Euxesta stigmatis Loew (Diptera:
Otitidae), on sweet corn in southern Florida. Proc. Fla.
State Hortic. Soc. 102: 370 Ð373.
Seal, D. R., and R. K. Jansson. 1993. Oviposition and development of Euxesta stigmatis (Diptera: Otitidae). Environ.
Entomol. 22: 88 Ð92.
Seal, D. R., R. K. Jansson, and K. Bondari. 1995. Bionomics
of Euxesta stigmatis (Diptera: Otitidae) on sweet corn.
Environ. Entomol. 24: 917Ð922.
Sivinski, J. 2000. Breeding habits and sex in families closely
related to the Tephritidae: opportunities for comparative
studies of the evolution of fruit ßy behavior, pp. 23Ð37. In M.
Aluja and A. L. Norrbom [eds.], Fruit ßies (Tephritidae):
phylogeny and evolution of behavior. CRC, Boca Raton, FL.
Sivinski, J., M. Aluja, G. Dodson, A. Freidberg, D. Headrick,
K. Kaneshiro, and P. Landolt. 2000. Topics in the evo-
January 2010
BRUNEL AND RULL: NATURAL HISTORY AND BEHAVIOR OF E. bilimeki
lution of sexual behavior in the Tephritidae. pp. 751Ð792.
In M. Aluja and A. L. Norrbom [eds.], Fruit ßies (Tephritidae): phylogeny and evolution of behavior. CRC,
Boca Raton, FL.
Stockley, P., M.J.G. Gage, G. A. Parker, and A. P. Moller.
1997. Sperm competition in Þshes: the evolution of
testis size and ejaculate characteristics. Am. Nat. 149:
933Ð954.
119
Vahed, K. 1998. The function of nuptial feeding in insects:
a review of empirical studies. Biol. Rev. 73: 43Ð78.
Yoon, J. S., M. T. Mathew, and R. E. Holman. 1983. Biology
of Euxesta quaternaria Loew (Diptera: Otitidae). Entomol. News 94: 122Ð126.
Received 12 June 2009; accepted 1 October 2009.