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Complicity or Conflict over Sexual Cannibalism? Male Risk Taking in the Praying Mantis Tenodera aridifolia sinensis

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Complicity or Conflict over Sexual Cannibalism? Male Risk Taking in the Praying Mantis Tenodera aridifolia sinensis

Abstract

Male complicity versus conflict over sexual cannibalism in mantids remains extremely controversial, yet few studies have attempted to establish a causal relationship between risk of cannibalism and male reproductive behavior. We studied male risk-taking behavior in the praying mantid Tenodera aridifolia sinensis by altering the risk imposed by females and measuring changes in male behavior. We show that males were less likely to approach hungrier, more rapacious females, and when they did approach, they moved more slowly, courted with greater intensity, and mounted from a greater distance. Similarly, when forced to approach females head-on, within better view and better reach of females, males also approached more slowly and courted with greater intensity. Thus, males behaved in a manner clearly indicative of risk avoidance, and we support the hypothesis of sexual conflict over sexual cannibalism.
vol. 168, no. 2 the american naturalist august 2006
Natural History Miscellany
Complicity or Conflict over Sexual Cannibalism? Male Risk Taking in the
Praying Mantis Tenodera aridifolia sinensis
Jonathan P. Lelito
*
and William D. Brown
Department of Biology, State University of New York, Fredonia,
New York 14063
Submitted June 24, 2005; Accepted May 5, 2006;
Electronically published July 12, 2006
abstract: Male complicity versus conflict over sexual cannibalism
in mantids remains extremely controversial, yet few studies have
attempted to establish a causal relationship between risk of canni-
balism and male reproductive behavior. We studied male risk-taking
behavior in the praying mantid Tenodera aridifolia sinensis by altering
the risk imposed by females and measuring changes in male behavior.
We show that males were less likely to approach hungrier, more
rapacious females, and when they did approach, they moved more
slowly, courted with greater intensity, and mounted from a greater
distance. Similarly, when forced to approach females head-on, within
better view and better reach of females, males also approached more
slowly and courted with greater intensity. Thus, males behaved in a
manner clearly indicative of risk avoidance, and we support the
hypothesis of sexual conflict over sexual cannibalism.
Keywords: sexual cannibalism, sexual conflict, mate choice, praying
mantis, Mantidae.
Sexual cannibalism in praying mantids is legendary, and
a great majority of species display sexual cannibalism at
least occasionally (reviewed in Elgar 1992; Maxwell 1999a).
Benefits of sexual cannibalism to the female are contro-
versial in some species (Arnqvist and Henriksson 1997;
Maxwell 2000), but in the Chinese mantis Tenodera ari-
difolia sinensis, the benefits are clear: females gain valuable
reproductive resources through cannibalism. When fe-
males consume more prey or larger prey, they lay larger
oothecae (egg cases) that contain more eggs, and they
ultimately produce a greater number of offspring (Eisen-
* E-mail: jpl207@psu.edu.
Corresponding author; e-mail: william.brown@fredonia.edu.
Am. Nat. 2006. Vol. 168, pp. 263–269. 2006 by The University of Chicago.
0003-0147/2006/16802-41154$15.00. All rights reserved.
berg and Hurd 1977; Eisenberg et al. 1981; see also Matsura
and Mooroka 1983 for Tenodera angustipennis). A single
ootheca may weigh 30%–50% of a female’s biomass and
thus represents a tremendous investment (Eisenberg et al.
1981; Hurd 1989). Yet in the field, females are often food
limited (Hurd et al. 1978, 1995), making males valuable
as a food source, and hungry females are more likely to
cannibalize males than are satiated females (Liske and Da-
vis 1987). Hurd et al. (1994) estimated that males in one
population of T. sinensis made up 63% of the diet of adult
females.
In contrast to these nutritional benefits to females, the
possibility that males may also benefit from sexual can-
nibalism remains extremely controversial (see Gould 1984;
Johns and Maxwell 1997). Unlike some sexually canni-
balistic spiders (e.g., Sasaki and Iwahashi 1995; Knoflach
and van Harten 2001; Andrade and Banta 2002; Foellmer
and Fairbairn 2003), male mantids can mate repeatedly
and potentially fertilize multiple females during their life-
time (Bartley 1982; Lawrence 1992; Hurd et al. 1994).
Sexual cannibalism obviously eliminates the possibility of
future mating for the male and thus imparts a clear cost—
the total loss of future reproduction. All else being equal,
this cost will generate strong sexual conflict over canni-
balism. Yet male mantids can initiate copulation even after
cannibalism has begun, and decapitation by cannibalism
may even increase copulatory behavior (Roeder 1935;
Liske 1991). Thus, precopulatory attacks by females may
not diminish a male’s mating success with the current
female and may even increase the chance of successfully
mating. One of the original theoretical models of sexual
cannibalism shows that a male should be willing to sacrifice
his life to an inseminated partner if he can expect little
subsequent mating and if his value as a food item would
allow the female to rear substantially more offspring (Bus-
kirk et al. 1984; see also Parker 1979; Polis 1981; Birkhead
et al. 1988; Maxwell 2000). More recent work on spiders
has shown that males may also achieve a paternity ad-
vantage through sexual cannibalism if cannibalism can ex-
tend the period of insemination, decrease the chance of
264 The American Naturalist
repeated mating by the female, or otherwise allow pref-
erential sperm usage (Andrade 1996; Schneider and Elgar
2001).
Our goal here is to distinguish between the alternative
hypotheses of male complicity versus sexual conflict over
sexual cannibalism in T. sinensis by testing how male be-
havior may change depending on the likelihood of being
eaten. As Gould (1984) pointed out, the model of male
complicity “makes good sense, but nature will match it
only if we can show that such males actively promote their
own consumption” (p. 14). Gould went on to argue that
he found “little persuasive evidence” (p. 16) based on the
descriptive accounts of male behavior (Roeder 1935; for
more recent accounts, see Liske and Davis 1987; Lawrence
1992; Kynaston et al. 1994; reviewed in Maxwell 1999a).
But remarkably, this question of whether male mantids
are complicit has never been experimentally resolved. Only
one study has attempted to test the causal relationship
between risk and male behavior (Maxwell 1999b). None
has focused on female hunger, possibly the most important
risk factor for males, given that hungry female mantids
are significantly more rapacious than satiated females in
T. sinensis (Liske and Davis 1987), Hierodula membranacea
(Birkhead et al. 1988), and Sphodromantis lineola (Kyn-
aston et al. 1994).
Most previous attempts to resolve the question of com-
plicity versus conflict in mantids have attempted to mea-
sure the costs and/or benefits of cannibalism on male re-
productive success, with the clear prediction that if the
costs of cannibalism exceed the benefits, there is conflict,
but if the benefits are somehow greater, there is complicity
(e.g., Birkhead et al. 1988; Maxwell 1998). The difficulty
of this approach, however, is that it has proven excep-
tionally difficult to collect reliable data on the reproductive
opportunities of male mantids in wild populations, making
it very difficult to measure the costs. Moreover, low mate
encounter rates for males may be the consequence of an
evolutionary history of sexual cannibalism rather than its
causal precursor (Andrade 2003; Fromhage et al. 2005).
Thus, the cost/benefit approach has been unable to resolve
the controversy over male complicity in sexual cannibalism
in mantids.
We address the question of complicity versus conflict
by studying the adaptive design of male mating behavior
in an experimental context that tests the causal relationship
between variable risk of cannibalism and male behavior.
We ask whether males switch their mating behavior ac-
cording to variation in the risk of being cannibalized. The
male complicity hypothesis predicts that males will engage
in behavior that actively facilitates, or at least passively
fails to avoid, acts of sexual cannibalism during and after
copulation. To the contrary, our results show that males
assess risk of cannibalism and that, given this risk, they
behave in a manner to reduce the likelihood of canni-
balism. Thus, male mantids are not complicit in canni-
balism, and we support the hypothesis of sexual conflict.
Material and Methods
Mantid Rearing
We reared mantids from oothecae, which were either pur-
chased from Carolina Biological Supply (Burlington, NC)
or collected from a wild population in Fredonia, New York.
We reared oothecae initially at room temperature and later
under an incandescent bulb that increased ambient tem-
perature and developmental rate. We misted the oothecae
with water daily.
Mantids hatched after 4–6 weeks. Nymphs were reared
individually in 500-mL plastic containers, fed an ad lib.
supply of Drosophila hydei, and misted daily. Malformed
or unusually inactive mantids were discarded. Rearing
containers were lined on the inside with fiberglass screen-
ing as a substrate for moving and perching. We also added
a slice of apple for moisture and to feed the flies until the
mantids consumed them. Diet was switched to juvenile
crickets, Acheta domesticus, after about 5 weeks, when
mantids reached their fourth instar. Mantids eclosed as
adults approximately 8 weeks after hatching.
Manipulating the Risk of Sexual Cannibalism
We used a two-by-two factorial experiment to test male
response to altered risk of sexual cannibalism. All mantids
were virgins at the beginning of the experiment. Treat-
ments included female hunger level and orientation of
male approach. To control female size and fecundity be-
tween hunger levels, all females in the experiment were
first fed ad lib. crickets for 24 days after adult eclosion.
Female body mass (measured to 0.01 mg on an A & D
HR-202 balance; A & D Engineering, Milpitas, CA)
showed a negative exponential increase over time (y p
, where mass and from adult
0.101
2.81xyp body x p age
emergence; , , ), with mass slow-t p 5.90 N p 16 P
! .001
ing toward an asymptote after about 20 days. Thus, by 24
days, females were near their maximum size, possessing
visibly distended abdomens, and body mass was indepen-
dent of subsequent experimental treatments (diet treat-
ment: , , ; orientation:F p 0.58 df p 1, 16 P p .46 F p
, , ). Females were then randomly0.19 df p 1, 16 P p .67
divided into either “satiated” treatment of ad lib. crickets
or “hungry” treatment of 4–5 days without food to begin
the experiment. All females that laid oothecae before the
experiment were returned to an ad lib. diet for another
24 days to regain fecundity. Males were fed ad lib. through-
out the experiment.
Sexual Conflict in a Praying Mantis 265
In the orientation treatment, males approached females
either head-on, the more risky treatment, or from behind,
the less risky treatment. Both Liske and Davis (1987) and
Maxwell (1999b) suggest that males in front of and within
the visual field of females are at greater risk. Our exper-
iment differs from these two studies in that male orien-
tation was manipulated so that males could not alter their
direction of approach throughout the experiment. We var-
ied the orientation of male approach by placing the female
at the end of a wooden plank (80 cm cm wide)long # 6
that was marked in 1-cm increments and then introducing
the male from the desired orientation. Once in place, a
female did not turn around until either she leapt aggres-
sively at the male or the male attempted to mount. The
initial distance of 80 cm is within the visual and che-
mosensory range of the mantids (Liske and Davis 1987).
Following Liske and Davis (1987), we illuminated the mat-
ing arena in an otherwise darkened room, allowing us to
observe without being seen by the mantids.
Mantids are difficult to rear, which restricts sample sizes.
To increase our data set on male risk taking, we tested 25
males under each of the four different treatment combi-
nations, for a total of 100 trials. Males were paired to the
same female for each of the four trials, and we randomly
determined the order of treatments experienced by each
male. Pairs were given 5–9 days between trials. To reduce
the risk of cannibalism and subsequent loss of data, the
three initial trials for each pair were terminated imme-
diately after the male mounted the female. Thus, we do
not report actual rates of sexual cannibalism. On the fourth
trial, pairs were allowed to mate.
Male Approach and Courtship Behavior
Tenodera sinensis courtship is described in detail by Liske
and Davis (1984, 1987). We recorded total approach speed
as the distance that the male traveled on foot toward the
female from the point of release, divided by the time taken
to travel this distance. Leap distance was the distance be-
tween the male and the female from which the male leapt
onto the back of the female to mount. The hypothesis of
sexual conflict over sexual cannibalism predicts that males
will approach more slowly and leap from a greater distance
when the risk of attack is greater. In 10 cases, males flew
away from the female rather than mounting them, and
this behavior is analyzed separately. Following Liske and
Davis (1987), we predicted that if males are risk avoiders,
they will increase courtship when the risk of cannibalism
is greater in order to better differentiate themselves from
other prey and pacify the females. Courtship by male T.
sinensis involves an upward thrusting of the forewing and
hindwings and a rhythmic bending motion of the abdo-
men at an angle of 0–90 (Liske and Davis 1987). We
judged variation in the degree, that is, the angle of ab-
dominal bending to represent differences in the intensity
of male courtship.
We recorded instances of aggressive behavior directed
at males by females. We judged a leap at the male and
strikes with the raptorial forelegs to be aggressive. We
judged lowering of the tibial claws to be submissive be-
havior (following Liske and Davis 1987); claw lowering
may be an indication of responsiveness to courtship. Dur-
ing two trials, females responded to males with defensive
deimatic displays—flashing the colored eyespots on the
inside of their forelimbs—but this behavior was too in-
frequent for analysis. Finally, for the trials in which pairs
were allowed to mate, we also recorded precopulatory
mounting duration as the time from mounting to genital
linkage, copulation duration as the time from linkage to
separation of the genitalia, and postcopulation duration
as the time from the end of intromission until the male
leapt off the female. Given the experimental design, the
sample size for mating behavior was small ( ), andN p 25
nonsignificant results should thus be viewed with caution.
Female Hunger Level
Subsequent to the experiment, we tested the assumption
that our treatment successfully altered female hunger. We
provided eight females from each diet treatment an ad lib.
supply of crickets and recorded the number eaten over 24
h.
Analyses
Individual males experienced each treatment combination
with a single female, and thus we analyzed the results on
approach speed, leap distance, and courtship using a
within-subjects ANOVA with pairs. The data forN p 25
approach speed and durations of the three stages of mating
(precopulation, copulation, and postcopulation) were nor-
malized by natural-log transformation before analysis. Fe-
male behavior and male flight away from females were
recorded as binary (yes/no) data and were analyzed using
McNemar tests for significant changes in behavior within
individuals (Sokal and Rohlf 1995). Each pair contributed
only a single set of measures of the durations of the three
stages of mating, and we analyzed these data by multi-
variate ANOVA.
We corrected the problem of elevated Type I statistical
error due to multiple testing by adjusting P values to con-
trol the false discovery rate (Benjamini and Hochberg
1995), as described by Verhoeven et al. (2005). As rec-
ommended by Neuha¨user (2004), when uncorrected P !
, we report both uncorrected and adjusted P values. We.05
report back-transformed means and 95% confidence in-
266 The American Naturalist
Figure 1: Relationship between female hunger treatment, male orien-
tation of approach, and speed at which males approached females. Means
are back transformed with back-transformed SE.
Figure 2: Relationship between female hunger treatment, male orien-
tation of approach, and distance from which males leaped onto the backs
of females. Means are shown SE.
tervals (CIs). The effect of diet treatment on cricket con-
sumption by females was analyzed by t-test.
Results
Our tests confirmed that food-restricted, “hungry” females
were indeed significantly hungrier than “satiated” females
given an ad lib. diet of crickets. Hungry females consumed
an average of crickets within 24 h after the6.0 0.33
experiment, whereas satiated females consumed only
crickets ( , , ). Thus,2.7 0.42 t p 6.2 df p 14 P
! .001
hungry females were more rapacious.
Male Approach to the Female
Both female hunger and the orientation of approach had
significant effects on male approach to the female. First,
some males chose to fly away from the female rather than
mount. Males flew away from hungry females more often
than they flew from satiated females, though the effect was
not significant after correcting for false discovery rate (8
of 50 [16%] trials vs. 2 of 50 trials [4%], respectively;
McNemar test: , , ,G p 3.85 df p 1 P p .049 P p
adj adj
). Orientation of approach had no significant effect.077
on the frequency of male flight (head-on: 7 of 50 [14%];
behind: 3 of 50 [6%]; , , ).G p 1.57 df p 1 P p .20
adj
Second, when males approached females, they ap-
proached hungry females significantly more slowly than
satiated females (within-subjects ANOVA: ,F p 25.76
, , ; fig. 1). They also ap-df p 1, 24 P ! .0001 P ! .00055
adj
proached females more slowly head-on than from behind
( , , , ). There wasF p 8.85 df p 1, 24 P p .007 P p .018
adj
no significant interaction effect ( , ,F p 0.98 df p 1, 24
).P p .33
Third, males leapt from their perches onto the backs of
hungry females from a significantly greater distance than
that from which they leapt onto satiated females (F p
, , , ; fig. 2). Orien-13.48 df p 1, 24 P p .001 P p .0044
adj
tation of approach had no significant effect on leap dis-
tance ( , , ), nor was there aF p 2.64 df p 1, 24 P p .12
significant interaction effect ( , ,F p 2.61 df p 1, 24 P p
)..12
Male Courtship Behavior
Female hunger and the orientation of approach also had
a significant effect on male courtship behavior. Males
showed greater abdominal bends when approaching fe-
males head-on ( ) than when approaching52.8⬚Ⳳ3.2
them from behind ( ; , ,10.8⬚Ⳳ0.2 F p 117.60 df p 1, 24
, ). Similarly, abdominal bends of maleP
! .0001 P ! .0011
adj
courtship were greater when directed at hungry females
( ) than at satiated females ( ;36.6⬚Ⳳ3.1 27.0⬚Ⳳ2.3
, , , ). There wasF p 5.89 df p 1, 24 P p .023 P p .042
adj
a significant interaction between hunger level and male
orientation of approach ( , , ,F p 6.51 df p 1, 24 P p .018
Sexual Conflict in a Praying Mantis 267
), with males providing uniformly low court-P p .040
adj
ship when approaching from behind (hungry females:
; satiated females: ) but differen-10.8⬚Ⳳ2.9 10.8⬚Ⳳ3.1
tiating between hungry and satiated females when ap-
proaching head-on (hungry females: ; satiated62.4⬚Ⳳ4.9
females: ).43.2⬚Ⳳ3.9
Female Behavior
Hungry females made predatory strikes at males signifi-
cantly more often than did satiated females (16 of 50 [32%]
times vs. 5 of 50 [10%] times, respectively; McNemar test:
, , , ). OrientationG p 8.72 df p 1 P p .003 P p .018
adj adj
of approach had no significant effect (head-on: 12 of 50
[24%] times; behind: 9 of 50 [18%] times; ,G p 2.89
adj
, ). In contrast, aggressive leaps by femalesdf p 1 P p .09
were affected more by the orientation of approach, though
this effect was not significant after correcting for false dis-
covery rate (head-on: 14 of 50 [28%] trials; behind: 4 of
50 [8%] trials; , , , ).G p 3.85 df p 1 P p .049 P p .15
adj adj
Diet treatment had no significant effect ( ,G p 0.11
adj
, ). There was no significant effect of eitherdf p 1 P p .75
treatment on the claw-lowering display of females (diet:
, , ; orientation: ,G p 0.48 df p 1 P p .49 G p 0.38
adj adj
,).df p 1 P p .54
Mating
Males that mated with hungry females had significantly
greater overall mounting duration than those that mated
with satiated females (multivariate ANOVA: Wilks’s
, , , ). This was duel p 0.65 F p 3.45 df p 3, 19 P p .037
to a difference in postcopulatory mounting by males.
Males remained on the backs of hungry females for
(back-transformed mean) 86.06 min (95% CI p 52.61
140.75 min) before dismounting but remained on sati-
ated females for only 28.62 min (95% –47.70CI p 17.18
min; , , ). The duration ofF p 10.42 df p 1, 25 P p .004
neither precopulatory mounting ( min, 95%mean p 5.44
–30.66 min; , , )CI p 0.96 F p 0.28 df p 1, 25 P p .61
nor copulation ( min, 95% mean p 207.00 CI p 107.22
399.63 min; , , ) differed sig-F p 0.003 df p 1, 25 P p .96
nificantly between diet treatments. There were no sig-
nificant correlations between the durations of precopu-
latory, copulatory, and postcopulatory mounting
(Pearson correlations, all ). Upon mounting, theP .64
male aligns its body to that of the female; therefore, it
is not surprising that orientation of initial approach had
no effect on mating duration (Wilks’s ,l p 0.99 F p
,,).0.08 df p 3, 19 P p .97
Discussion
Despite the notoriety of sexual cannibalism in mantids,
there has been no strong experimental evidence to dem-
onstrate either the complicity of males or active male risk
avoidance. Most inference comes from purely descriptive
accounts of male mating behavior (Roeder 1935; Liske and
Davis 1987; Lawrence 1992; Kynaston et al. 1994; Maxwell
1998). Our results show that males alter their approach,
mounting behavior, and courtship depending on the risk
imposed by their prospective mate. These results clarify
two major issues surrounding the controversy over male
complicity versus conflict during sexual cannibalism. First,
the change in male behavior with the experimental ma-
nipulations shows that male mantids are assessing varia-
tion in the risk imposed by the females. Thus, males appear
to be cueing in on some aspect of female phenotype or
behavior indicative of risk. Orientation itself is one obvious
cue, but even at the same orientation, males appear to
judge the risk of a hungry versus a satiated female when
female fecundity is controlled. Courting males may alter
their behavior in response to visual or olfactory cues given
by the female, but this warrants further study.
Second, male response to female hunger and orientation
is clearly not consistent with male complicity in sexual
cannibalism. Males do not facilitate being grasped by the
raptorial front legs of their mate; instead, as risk increases,
they become more cautious in their approach of females,
in a manner clearly indicative of risk avoidance and male-
female conflict over sexual cannibalism.
Male Responses to Female Hunger
Hungry female Tenodera sinensis are more rapacious, make
more predatory strikes at males, and impose a greater risk
of sexual cannibalism than satiated females (Liske and
Davis 1987). Males were more likely to fly away from
hungry females than satiated females. When males ap-
proached hungry females, they moved more slowly and
mounted from a greater distance. This “cautious” ap-
proach by males matches our a priori expectations of an
effective risk avoidance tactic. Maxwell (1999b) found that
male Iris oratoria mantids were less likely to mount females
in poor condition (i.e., relatively low body mass), though
it was not clear how condition related to hunger, fecundity,
or some other factor contributing to the state of the female.
For example, in contrast to our results, female I. oratoria
in poor condition were less likely to attack males; however,
all females were maintained on the same diet regime, and
thus the lower attack rate and poor condition might both
be related to the overall lower rapacity of these females.
Male T. sinensis also displayed more intense courtship
toward hungry females than satiated females. We predicted
268 The American Naturalist
that if males were risk avoiders, they would increase court-
ship when the risk of cannibalism was greater in order to
better differentiate themselves from other prey and pacify
the females (Liske and Davis 1987). This prediction is
supported. To our knowledge, the only similar example of
a change in male behavior in response to experimentally
altered risk is the study by Elgar and Fahey (1996) dem-
onstrating that male orb-weaving spiders increase their
attempts to copulate after females are presented with sub-
stitute prey. Fromhage and Schneider (2005) subsequently
showed that this behavior by males significantly reduced
the risk of sexual cannibalism. We note that for both the
spider and the mantid, these changes in male behavior are
indicative of a direct trade-off between a male’s motivation
to reproduce and his motivation to escape death.
Male Responses to the Orientation of Approach
Males were also more cautious when approaching females
head-on versus from behind. A head-on approach puts
males well within the visual field of the female and in the
most convenient position for an attack. When approaching
females head-on, males moved more slowly and courted
with greater intensity. These results match Liske and
Davis’s (1987) correlative data showing that male T.
sinensis slowed down as they approached females head-on
but sped up as they approached females from behind.
Maxwell (1999b) experimentally set the initial orientation
approach by male I. oratoria but allowed males to adjust
their orientation after release. He found that those mantids
that started from the risky head-on position typically
switched to approach from behind. This switch in ori-
entation could be interpreted as either risk avoidance or
simply facilitation of proper alignment for mounting.
Mating
After mating, males remained with hungry females for a
substantially longer period compared to well-fed females.
This behavior also matches our prediction based on risk
avoidance. Lawrence (1992) pointed out that “dismount-
ing is more dangerous to a male than remaining on the
back of a female” (p. 576), and when they do dismount,
males invariably drop or fly away quickly from the female,
acts that quickly get them out of reach of the female.
Prolonged postcopulatory mounting suggests that males
with hungry females are more selective of proper situation
for a safe dismount. Thus, each component of male mating
behavior—approach, courtship, and mounting—becomes
more cautious as the risk of sexual cannibalism increases.
Males employ a tactic of risk avoidance, and these results
on the functional design of male mating behavior strongly
support the hypothesis of sexual conflict over sexual can-
nibalism in mantids.
Acknowledgments
We thank the anonymous reviewers for helpful comments
on the manuscript. This work was funded by a Holmberg
Summer Research Fellowship to J.P.L. and an Undergrad-
uate Research grant to J.P.L. from the College of Natural
and Social Sciences, State University of New York at
Fredonia.
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Associate Editor: Allen J. Moore
Editor: Jonathan B. Losos
... In the current study we only used initially virgin females that are 17-22 days old during events of mating and cannibalism. Previous work shows that females at this stage of the breeding season are sexually receptive and are accumulating body mass at a rapid rate (Lelito and Brown 2006), suggesting that this is the prime period of oogenesis. We randomly assigned adult females to one of three treatment groups: (1) "cannibal" females (n = 11), (2) "starved" females (n = 11), and (3) "cricket consumer" females (n = 11). ...
... These results are not surprising given that male mantids are much larger than other typical prey of female mantids and mating is probably happening during the most active period of weight gain by females (Lelito and Brown, 2006), which is probably indicative of active oogenesis. Brown and Barry (2016) allowed T. sinensis females to cannibalize males that contained radiolabeled amino acids and showed that male-derived nutrients were disproportionately allocated to eggs and female reproductive tissues. ...
... Multiple species have been observed displaying sexual cannibalism or predatory behavior against potential mates at frequencies near or exceeding this 32% extinction threshold. Tenodera sinensis females on a limited diet make predatory strikes against approaching males in 32% of laboratory encounters (Lelito and Brown 2006), Miomantis caffra females cannibalize males in 62% of laboratory encounters regardless of feeding regime (Walker and Holwell 2015), and Mantis religiosa females cannibalize 31% of the males they encounter in the field (Lawrence 1992). As such, the greater egg production by females that consume males, as we see in T. sinensis, may enable stable population sizes despite the removal of reproductive males from the population. ...
Article
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The fecundity benefit of sexual cannibalism is a key parameter of models for the evolution and population-level consequences of sexual cannibalism. Previous studies of praying mantids that have attempted to measure the change in egg production following cannibalism have yielded inconsistent results, possibility due to differences in female ages and background diets. We studied the effect of cannibalism on egg production and egg laying in the Chinese praying mantid (Tenodera sinensis), standardizing female age and mating status, and maintaining females on diets that reflect natural rates of foraging. We experimentally assigned females to one of three treatments: cannibal, non-cannibal, or cricket consumers that received an additional diet of crickets (Acheta domesticus) roughly equivalent to the mass consumed by cannibals. We show that cannibalistic females that consume multiple males produced significantly more eggs and laid more eggs in their first ootheca (egg case) compared to non-cannibals. This result supports the hypothesis that sexual cannibalism in T. sinensis is a female foraging strategy that provides resources to increase fecundity. The increase in egg production by cannibals was similar to that of the cricket consumer females suggesting that male mantids are equivalent to other prey, per unit body mass, in terms of their effects on egg production.
... In the wild, European mantis (Mantis religiosa) females cannibalised potential mates in 31% of encounters (Lawrence, 1992), with similar rates seen in other mantids (Hierodula membranacea, Birkhead, Lee, & Young, 1988; T. sinensis, Lelito & Brown, 2006). ...
... It is fairly common for female spiders and insects to cease to attract males once they have mated, particularly if approaching a female is potentially costly due to cannibalism risk (Lelito & Brown, 2006;Gaskett, 2007). Attractiveness to males is often thought to be associated with pheromone production, so a reduction in the attractiveness of mated females is likely to be due to reduced pheromone production (Roberts & Uetz, 2005). ...
... However, if aggression in males of cannibalistic species is fixed across contexts, or aggression is correlated with other potentially maladaptive behaviours, then the evolution of male juvenile aggression may be constrained by the costs of males continuing to be aggressive into adulthood. For example, aggressive adult males may be bolder in the presence of females and thereby increase their risk of being cannibalised (Lelito and Brown, 2006). ...
Thesis
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The original idea for this thesis was conceived whilst I was working (voluntarily) in the behavioural ecology lab at Macquarie University, Sydney. My initial thoughts for the project centred around investigating the ways in which the environment might change such that sexual cannibalism increased population extinction risk. Whilst this is the running theme throughout the work presented here, I also, in various places, allude to the notion that there may be many reproductive behaviours that could very quickly become maladaptive in response to rapid environmental change. As I am keen to publish most, if not all of the data chapters in this thesis, each chapter is written independently of the others and structured in the style of a paper.
... For a subset of these organisms, this is a result of species-specific stereotypic behaviour. For instance, some male praying mantises and spiders go on to mate with females despite the risk of being cannibalized as part of the mating process (Lelito and Brown 2006;Prokop and Václav 2005). In some species of exploding ants, "during territorial combat, workers…sacrifice themselves by rupturing their gaster and releasing sticky and irritant contents of their…mandibular gland reservoirs to kill or repel rivals" (Laciny et al. 2018, 1-2). ...
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Much of the literature on the free energy principle (FEP) has focused on how organisms maintain homeostasis amidst a constantly changing environment. A fundamental feature of the FEP is that biological entities are “hard-wired” towards self-preservation. However, contrary to this notion, there do exist organisms that appear to seek out rather than avoid conditions that pose an elevated risk of serious injury or death, thereby jeopardizing their physiological integrity. Borrowing a term used in 1990s popular culture to refer to stunt performers like Evel Knievel, these organisms that exhibit such behavioural characteristics can be referred to as daredevils. This paper presents the case of daredevils as a challenge to the FEP’s homeostasis- and optimization-based construal of biological systems. It also introduces three possible explanatory strategies by which the FEP can account for daredevils. The broader objective of the paper is to enhance the FEP’s ability to account for a diverse range of complex behaviour.
... Given the opportunity of male's additional mating is limited, fitness loss in cannibalised males diminishes, resulting in the resolution of sexual conflict and the evolution of male suicidal behaviour facilitating sexual cannibalism (Andrade, 1996). By contrast, large fitness costs to the male due to sexual cannibalism may lead to counter-adaptation in the male, in which selection favours male mating traits avoiding cannibalism (Barry et al., 2009;Fromhage & Schneider, 2005;Gemeno & Claramunt, 2006;Kadoi et al., 2017;Lelito & Brown, 2006;Moya-Laraño et al., 2004;Scardamaglia et al., 2015). Mantid males are known to encounter multiple females in experimental (Inoue & Matsura, 1983) and wild (Christensen & Brown, 2018;Maxwell, 1998) populations. ...
Article
The timing and frequency of female mating are important determinants of male reproductive success. Elucidating reproductive phenology is crucial to understand the evolution of mating behaviour and mating systems. Mate encounter rate is a key variable for understanding the evolutionary consequences of sexual cannibalism. However, remarkably little is known about female mating frequency in wild populations in mantids, charismatic insects that exhibit sexual cannibalism. The authors examined the reproductive phenology of a wild population of the sexually cannibalistic praying mantid Tenodera angustipennis, and paid special attention to female mating frequency. Field surveys throughout two reproductive seasons were combined with survival model analysis to estimate the phenology of eclosion, adult sex ratio, female first mating, and oviposition, allowing quantification of time windows for reproductive maturation and female mating. Genetic paternity analysis using newly developed microsatellite markers revealed that females mated with two to six males on average before oviposition in the wild. The results provide a comprehensive record of the reproductive phenology and female mating frequency in a wild mantid population, and insight into the evolution of male mating behaviour under sperm competition and sexual cannibalism. The reproductive phenology and female mating frequency of a wild population of the praying mantid Tenodera angustipennis were examined based on field surveys and genetic paternity analyses. Females required 26 days for reproductive maturation and mated on average 2–6 males within 13 days after the first mating. The results of the present study indicate large nutritional requirement for the female and intensive sperm competition for the male, providing insight into the evolution of male mating behaviour under sexual cannibalism and sperm competition. A Tenodera angustipennis female mounted by two males in the rice field
... In the spider Nephila fenestrata, males that mate with idle females suffer more injuries than males that mate with feeding females (Fromhage & Schneider, 2005), suggesting that inopportune approaches can be costly. Similarly, males of some praying mantis species approach females with great caution to avoid being captured (Barry et al., 2009;Lelito & Brown, 2006). However, the extent to which male activity levels mediate the likelihood of sexual encounter and female attack in these and other cannibalistic taxa remains unclear. ...
Article
Behaviours that are consistent across contexts (also known as behavioural syndromes) can have evolutionary implications, but their role in scenarios where the sexes conflict, such as sexual cannibalism, is poorly understood. While some research has focused on aggressive personality in females and its role in determining cannibalistic attack, effects of male personality have rarely been explored. Male activity as a personality trait could be an important mediator of sexual cannibalism if it modulates how quickly or carelessly males approach females, but such a relationship has never been tested. Here, we used the springbok mantis, Miomantis caffra, to explore effects of male activity levels and female aggressiveness on mating behaviour and sexual cannibalism. We found that male activity and subadult female aggressiveness were repeatable, although the latter only marginally so. Females that were aggressive as juveniles were not more likely to cannibalize males when adult following physical interaction, but males made physical contact with these females sooner and more often. More active males were both faster and more likely to interact with females, but were not more likely to be cannibalized in the process. We also found that female age influenced sexual interactions: younger females were more likely to cannibalize males. Taken together, our results suggest that both male and female personality influence the likelihood of sexual encounter, but have little effect on the likelihood of cannibalism. Our study highlights the potential for the personality traits of both sexes to influence mating dynamics in sexually cannibalistic species.
... The male's successful minimization of potential prediction error does not at all lead to maintaining the stability of its organism (cf. Lelito, Brown, 2006.) 60 However, one can defend Friston's approach by claiming that only some mechanisms are homeostatic, while others are allostatic. ...
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The purpose of this paper is to provide a systematic review of the Predictive Processing framework (hereinafter PP) and to identify its basic theoretical difficulties. For this reason, it is, primarily, polemic-critical and, secondarily, historical. I discuss the main concepts, positions and research issues present within this framework (§1-2). Next, I present the Bayesian-brain thesis (§3) and the difficulty associated with it (§4). In §5, I compare the conservative and radical approach to PP and discuss the internalist nature of the generative model in the context of Markov blankets. The possibility of linking PP with the free energy principle (hereinafter FEP) and the homeostatic nature of predictive mechanisms is discussed in §6. This is followed by the presentation of PP's difficulties with solving the dark room problem and the exploration-exploitation trade-off (§7). I emphasize the need to integrate PP with other models and research frameworks within cognitive science. Thus, this review not only discusses PP, but also provides an assessment of the condition of this research framework in the light of the hopes placed on it by many researchers. The Conclusions section discuss further research challenges and the epistemological significance of PP.
... Rather than responding with coercion, however, males typically employ cautious strategies to secure matings and avoid cannibalism [10]. Putative examples of such strategies include males using stealth during mating approaches [11][12][13][14], courting females with a decoy nuptial gift [15], playing dead when females attack [16,17], and preferentially mating with females that are feeding [18][19][20] or moulting [21,22]. Rare examples of males mating coercively rather than cautiously can be found in some sexually cannibalistic spiders, where courting males immobilize females for mating by biting them [23], injecting them with venom [24], emitting airborne chemicals [25], or tying them up with silk [26]. ...
Article
Sexual conflict can generate coercive traits in males that enhance mating success at the expense of female fitness. Pre-copulatory sexual cannibalism—where females consume males without mating—typically favours cautious rather than coercive mating tactics, and few examples of the latter are known. Here, we show that males of the highly cannibalistic springbok mantis, Miomantis caffra , wrestle females during pre-mating interactions. We find that most initial contacts between males and females involve a violent struggle whereby each sex tries be the first to grasp hold of the other with their raptorial forelegs. When females win the struggle, they always cannibalize males. However, when males grasp females first, they dramatically increase the chance of mating. We also find striking evidence that, on some occasions, males wound females with their fore-tibial claws during struggles, resulting in haemolymph loss and scar tissue formation. Taken together, our results show how males can overcome the threat of cannibalism by coercively wrestling females. We argue that pre-copulatory injury in this species is likely to be a negative pleiotropic side-effect of coercive mating behaviour and foraging morphology.
Book
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Praying Mantises of the United States and Canada, Second Edition January 2019 297 pages, 183 illustrations, 120 color photographs There are 28 different species of Mantodea within 16 genera now listed for the U.S. and Canada. One newly listed invasive species, Statilia maculata, is documented, raising the total number of introduced species to seven—25% of the region’s Mantodea. Second edition text includes: -New dichotomous key -Genus and species treatment for Statilia maculata -Updated descriptions, morphometry, natural history and distribution range maps for all 28 species found within this region -Addition of several new photographs of live specimens -Discussion of need for conservation efforts
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Book
Full-text available
This peer reviewed text includes a dichotomous key to all 15 genera of Mantodea found in the U.S. and Canada. Extremely detailed descriptions are provided for each of the 27 species found within this region, including two newly listed invasive species and two newly described species. One new genus is established along with several taxonomic revisions and clarifications. Species treatments include taxonomic illustrations, precise morphological descriptions, accurate morphometry, complete natural history documentation, exhaustive historical literature review, and detailed distribution range maps. There are 183 illustrations contained within the 291 pages of text, including 115 color photographs of live specimens.
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Popular procedures to control the chance of making type I errors when multiple statistical tests are performed come at a high cost: a reduction in power. As the number of tests increases, power for an individual test may become unacceptably low. This is a consequence of minimizing the chance of making even a single type I error, which is the aim of, for instance, the Bonferroni and sequential Bonferroni procedures. An alternative approach, control of the false discovery rate (FDR), has recently been advocated for ecological studies. This approach aims at controlling the proportion of significant results that are in fact type I errors. Keeping the proportion of type I errors low among all significant results is a sensible, powerful, and easy-to-interpret way of addressing the multiple testing issue. To encourage practical use of the approach, in this note we illustrate how the proposed procedure works, we compare it to more traditional methods that control the familywise error rate, and we discuss some recent useful developments in FDR control.
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Sexual cannibalism, in which a male is eaten by his mate following copulation, is expected to convey a selective advantage to the male under certain conditions. As shown quantitatively, the phenomenon is expected when 1) a male can mate only a few times in his lifetime and 2) the cannibalism significantly increases the number and/or viability of eggs fertilized by his own sperm. The expected number of male matings appears to be the more important of these 2 conditions. Phenomena selecting for sexual cannibalism appear more closely related to paternal investment strategies than to ecological factors associated with other forms of cannibalism. -from Authors
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Mating systems are frequently shaped by conflicts over reproductive interests between males and females. Sexual cannibalism can be an especially dramatic manifestation of such conflicts. However, the resolutions of this conflict differ among sexually cannibalistic spider species. Cannibalism may be in the interest of both sexes when females consume males as a foraging decision to improve fecundity and/or males sacrifice their bodies to increase fertilization success. In other species, females exert sequential choice of partner by selectively terminating copulation through cannibalism while males fail to obtain a paternity advantage. Here, we investigate the adaptive value of cannibalism in the orb-web spider Nephila plumipes where 60% of males do not survive copulation. Virgin females in poor condition are more frequently cannibalistic and more likely to kill large males, but the frequency of cannibalism among mated females is not influenced by these factors. Instead, males that mate with mated females increase their fertilization success by being cannibalized. Cannibalized males generally mate for longer, but longer copulations correspond with increased paternity only in mated females. The amount of sperm from particular males that a female stored was not influenced by any of the measured variables. The number of sperm stored was not related to paternity, nor was there any detectable reduction in sperm number after females had reproduced. Our data suggest that the conflict between the sexes differs between virgin and mated females. Females should always cannibalize a male, but males only gain from cannibalism when mating with mated females, not when mating with virgin females. Interestingly, the frequencies of cannibalism are not different in matings with virgin or mated females. Key words: cannibalism, foraging, mating, paternity advantage. [Behav Ecol 12:547–552 (2001)]
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Comparative studies between adult mantids (Tenodera ardifolia sinensis) in field populations and cohorts maintained in the laboratory on ad lib. diets suggest that females in field populations were food-limited. Food limitation apparently occurred in two cases during the time of acquiring energy to produce oothecae and in one case prior to maturation. In each case the net result was decreased fecundity We recognize two distinct components to the life history food requirements of this species: (1) the food required to reach maturity, and (2) the additional food required by females to produce oothecae. Our data suggest that food availability for nymphs affects initial sizes of adults, which in turn determines potential weight gain during the adult portion of the life cycle. Both the magnitude of this potential and the extent to which it is realized affects fecundity. The constraints imposed on either food component by membership in, and reliance upon, a seasonal insect community have implications for the ecological success of this introduced species.
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Adult populations of the mantid, Tenodera sinensis (Saussure) initially were male-biased, but females outnumbered males by the end of the life cycle because mortality was higher among males than among females. Male mantids were the most frequent items in the diet of females during oogenesis, when food limitation generally is greatest. Males had an 83% chance of escaping cannibalism during any given encounter with a female; however, females continued to attract males after first mating, raising the cumulative probability of male death with increasing number of intersexual encounters. We suggest female mantids continue to attract and cannibalize males beyond their need for sperm as a strategy to alleviate food limitation during oogenesis. This is more parsimonious than the adaptive suicide hypothesis, in which male fitness is enhanced by investment of his biomass in his offspring, since our hypothesis does not require that the victim share parenthood with his cannibal.
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Two experimental densities of mantids (Tenodera ardifolia sinensis Saussure) were introduced into replicated field plots with controls in the spring of 1975. These populations, and the arthropod component of the community, were sampled for the duration of the maturation period for Tenodera terminating in late July. Examination of survivorship for mantis nymphs revealed an apparent density-independent mortality early in the season, followed by a density-dependent mortality later. Rate of maturation was also density-dependent, with the high density plots exhibiting a slower rate. Food limitation was not a direct density-dependent limitation either to survivorship or development rate, since no differences were found in the arthropod component of the community between density treatments, or between treatments and control plots.
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The relationship between egg-case weight and number of nymphs emerging for the Chinese mantis (Tenodera ardifolia, sinensis Saussure) was significant (r = +0.74, P < .01). The temporal pattern of emergence suggests adaptive strategies for avoidance of both predation and cannibalism.