the effect of pair formation on diel calling patterns in two cricket species,Gryllus veletis andGryllodes sigillatus (Orthoptera: Gryllidae)

After pair formation, male crickets should reduce calling to minimize the risks to males of attracting predators and/or rivals. We tested this hypothesis in two cricket species, one in which males exhibit a high mating propensity (Gryllus veletis)and another in which the mating propensity of males is constrained by the manufacture of elaborate, bipartite spermatophores (Gryllodes sigillatus).Calling durations of male G. veletisdeclined precipitously after the introduction of females but remained unchanged in G. sigillatus.We attribute the asymmetric effect of female proximity on male calling to differences in the mating propensity of males of the two species. Male G. veletisabstain from further calling in favor of repeated matings with the same female. Male G. sigillatusprobably lack the opportunity to mate repeatedly with the same female and, thus, resume calling shortly after mating to increase their probability of attracting additional mates.     

Mating behavior of male deer ticksIxodes dammini (Acari: Ixodidae)

To analyze the sexual behavior of male black-legged deer ticks Ixodes dammini,we collected ticks infesting 202 white-tailed deer. On average, 17.7 males and 8.8 females infested each deer. Field-collected males copulated with a mean of 2.25 females, and virgin males mated with 2.4 females. On experimental hosts, males established sexual contact with feeding females and repelled other males, and about half remained paired after their mate detached. Engorged females continue to be receptive, and males mate more readily with them than with nonfed females. We conclude that male I. damminiare endowed with a repertoire of behaviors which favor an opportunistic mating before seeking a host and a preference for mating with feeding females on the host accompanied by tenacious mate guarding.     

Sexual selection at varying population densities in male field crickets,Gryllus veletis andG. pennsylvanicus

Male field crickets call and attract females or they silently search for females in the vicinity of calling males. At high population densities, fewer calling sites are available, defense of calling sites is costly, and an increased proportion of matings should result from searching behavior. To test these predictions, individually marked field crickets, Gryllus veletisand G. pennsylvanicus,were observed for 10 h nightly in large outdoor arenas at relatively high and low densities (2020 and 55, males and females). Data were gathered on body weight, calling duration, movement, and mating frequency for individual crickets. These observations showed that variance in male mating success was significantly greater at a low density in G. pennsylvanicus,and calling duration correlated with mating success at this density. Direct selection on a trait was estimated as the partial regression coefficient (selection gradient, ) and the total selection was estimated (direct and indirect selection on correlated traits) as the covariance (standardized intensity of selection, s) of the trait on the relative mating success. Direct selection favored increased movement at a high density in G. veletis,and direct and total selection favored increased calling duration at a low density in G. pennsylvanicus.Most other comparisons were not statistically significant. The data are discussed in terms of density-dependent fluctuations in sexual selection on correlated male traits.     

Pheromonal emission during the mating behavior ofEurycotis floridana (Walker) (Dictyoptera: Blattidae)

The sexual behavior of males and females ofEurycotis floridana was investigated and the various associated behavioral sequences are described. Olfactometer data proved that the male produces a volatile sex pheromone attractive at a distance to conspecific females. The male initiates courtship behavior by exposing the glandular areas on the anterior parts of abdominal tergites 2, 7, and 8. This male calling behavior was observed throughout the day. The males can mate when 8 days old, whereas virgin females are sexually receptive 18 days after becoming adults. Once attracted near the male, the female opens her genital atrium and climbs on the back of the male, where she feeds on the glandular secretions that oozed around a little tuft of setae on the first tergite. These setae are mechanoreceptors and they are stimulated when licked by the females, which informs the male that she is in a proper position for copulation.     

Floral sex ratio variation in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis Ajima et Satomi (Liliaceae)

Intrapopulation and interpopulation variations in floral sex ratio in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis (Liliaceae) were examined. The relative ratio of male flowers to total flowers (male and perfect flowers) decreased with plant size, suggesting size-dependent gender modification. The relative ratio of male flowers per population-basis is negatively correlated with the mean number of perfect flowers. Since the number of perfect flowers proportionally increased with plant size, populations showing low maleness consist of relatively bigger plants and are considered to be in high-quality environment. On the other hand, the relative ratio of male flowers per population basis is independent of female frequency in the population. Plasticity in gender expression probably plays an important role of maintenance of gynodioecy inC. japonica var.kurohimensis.     

Mate recognition in the Aphis fabae complex: daily rhythm of release and specificity of sex pheromones

The two subspecies of the host-alternating black bean aphid, Aphis fabae Scopoli, used in this study have different secondary host plants but reproduce sexually in autumn on the same host plant, spindle, Euonymus europaea L. In both Aphis fabae fabae Scopoli and A. f. solanella Theobald the percentage of adult mating females (oviparae) calling (releasing sex pheromone) each day increased with age up to day 8. During the course of a day the mating females of A. f. solanella called most actively early in the morning and then showed a gradual decrease in calling activity. In contrast, few A. f. fabae called early in the day and were most active around midday, after which the incidence of calling decreased slightly, with 50% still calling in the evening. In both taxa the activity of the males in the absence of mating females paralleled the calling activity of their respective females. In an olfactometer, males showed a marked preference for the sex pheromone released by conspecific females over that of the other subspecies and did not respond to the odour of spindle. Thus, as in the other species of aphids there are specific mate recognition systems in A. f. fabae and A. f. solanella, which are likely to reduce the incidence of hybridisation.     

Courtship song, male agonistic encounters, and female mate choice in the house cricket,Acheta domesticus (Orthoptera: Gryllidae)

Whether female crickets choose among males based on characteristics of the courtship song is uncertain, but in many species, males not producing courtship song do not mate. In the house cricket,Acheta domesticus, we examined whether a female chose or rejected a male based on his size, latency to chirp, latency to produce courtship song, or rate of the high-frequency pulse of courtship song (“court rate”). We confirmed that females mated only with males that produced courtship song, but we found no evidence that the other factors we measured affected a female’s decision to mate. In addition, we investigated whether the outcome of male agonistic encounters affected the subsequent production of courtship song. In one experiment, we observed courtship and mating behavior when a single female was placed with a pair of males following a 10-min interaction period between the two males. Winners of male agonistic encounters had higher mating success. However, winners and losers of agonistic encounters were not different in their likelihood or latency to produce courtship song or in the number of times they were disrupted by the other male in the pair. In a second experiment, we allowed two males to interact for a 10-min period, but following this interaction period, we placed a female with each male separately and observed courtship and mating behavior. The mating success of winners and losers was not different under these circumstances, and we found no differences between winners and losers in any subsequent courtship or mating behavior examined. We conclude that winning agonistic encounters influences a male’s mating success in ways other than his production of courtship song and this effect is lost when winning and losing males are separated and each is given an opportunity to mate.     

Reproductive isolation inProkelisia planthoppers (Homoptera: Delphacidae): Acoustic differentiation and hybridization failure

Males and females of Prokelisia marginata (Van Duzee) and Prokelisia dolusWilson communicate through substrate-transmitted vibrations. The acoustic signals (attraction and courtship calls) of these planthoppers are effective in mate location, attraction, and mate choice. Attraction calls are structurally distinct for both species and differ in pulse type, pulse repetition rate, and pulse duration. Using playback of prerecorded calls, individuals discriminated between conspecific and heterospecific signals. Depending on the sex and species, response calls were produced three to eight times more frequently to conspecifics than to heterospecifics. However, acoustic signals alone did not explain reproductive isolation and hybridization failure in these two congeners. Some heterospecific pairs called, courted, and attempted to join genitalia, but no connections were successful and no progeny were produced. Thus, acoustic behavior is not a guaranteed premating isolating mechanism in no-choice situations. Other courtship behaviors and possibly morphological differences in genitalia also contributed to their isolation. Females displayed a variety of rejection behaviors to conspecific and heterospecific males, suggesting that sexual selection (female choice), in addition to species recognition, may be an important force in the evolution of the acoustic signals of planthoppers. Although signal structure was not dependent on wing form (planthoppers exhibit wing dimorphism), the age when females first began to call was related to wing form. Brachypterous (flightless) females of both species began calling early in adult life (day 2), whereas macropterous (migratory) females began calling later in adult life (day 6). This pattern is consistent with the oogenesis-flight syndrome, in which reproductive maturity is delayed until after migration occurs.     

Sexual signal loss,pleiotropy, and maintenance of a male reproductive polymorphism in crickets

Pleiotropy between male signals and female preferences can facilitate evolution of sexual communication by maintaining coordination between the sexes. Alternatively, it can favor variation in the mating system, such as a reproductive polymorphism. It is unknown how common either of these scenarios is in nature. In Pacific field crickets (Teleogryllus oceanicus) on Kauai, Hawaii, a mutation (flatwing) that segregates as a single locus is responsible for the rapid loss of song production in males. We used outbred cricket colonies fixed for male wing morph to investigate whether homozygous flatwing and normal-wing (wild-type) females differ in responsiveness to male calling song and propensity to mate when paired with either a flatwing or normal-wing male in the presence or absence of courtship song. Flatwing females were less likely to mount a male than normal-wing females. Females of both genotypes showed a preference for normal-wing males and were more likely to mate in the presence of courtship song; normal-wing females were particularly likely to mate with song. Our results show that negative pleiotropy between obligate male silence and female mating behavior can constrain the evolution of sexual signal loss and contribute to the maintenance of a male reproductive polymorphism in the wild.     

Emergence, Mating, and Postmating Behaviors of the Oriental Beetle (Coleoptera: Scarabaeidae)

In a previous field-trapping study of the oriental beetle, Exomala orientalis (Waterhouse), by using synthetic sex pheromone on golf course fairways, numerous males were observed and trapped during the hours of peak mating activity. However, very few beetles were observed in the same areas when synthetic pheromone was absent. To investigate the hypothesis that mating in nature occurs cryptically within vegetation at the soil surface, laboratory studies on female emergence and pheromone release, male emergence and mate-locating, and female and male mating behaviors were conducted. Mate acquisition and copulation occurred on the soil surface near the female emergence site, with both sexes engaging in pheromone-mediated behaviors after having emerged from the soil. A highly stereotyped female pheromone release, or calling, behavior was observed, consisting of insertion of the female's head into the soil and elevation of the tip of her abdomen into the air. Bioassays conducted in a wind tunnel that simulated a turf fairway environment showed that walking and flying were both important in the upwind response of males to females. Mating and copulation occurred without an obvious complex courtship, but observations of postmating behaviors suggested that mate guarding occurs.     

Mate finding in the forest cockchafer, Melolontha hippocastani, mediated by volatiles from plants and females

The response of the forest cockchafer, Melolontha hippocastani F. (Coleoptera, Scarabaeidae), towards volatiles emitted by different host plants and conspecifics was tested in field experiments during the flight period at dusk. Funnel traps containing artificially damaged leaves from the host plants Carpinus betulus L. and Quercus rubra L., as well as from the non‐host plant Prunus serotina Ehrh. caught significantly more beetles than empty control traps. On the other hand, traps baited with undamaged leaves from Q. rubra did not catch significantly more beetles than empty controls. Leaves from C. betulus damaged by beetle feeding did not attract more beetles than artificially damaged leaves. By use of gas chromatography coupled with electroantennographic detection (GC‐EAD) electrophysiological responses of males and females were shown for 18 typical plant volatiles. A synthetic mixture of selected typical green plant volatiles was also highly attractive in the field. A total of 9982 beetles was caught during the field experiments, among them only 33 females. This suggests that attraction to damaged foliage during flight period at dusk is male‐specific. Field experiments testing the attractiveness of female M. hippocastani towards conspecific males by employing caged beetles and beetle extracts indicated that males of M. hippocastani use a female‐derived sex pheromone for mate location. On wired cages containing either unmated feeding females, or unmated females without access to foliage, or feeding males in combination with extracts from unmated females, significantly more males landed during the flight period than on comparable control cages containing feeding males or male extracts. A possible scenario of mate location in M. hippocastani involving feeding‐induced plant volatiles and a female‐derived sex pheromone is discussed.     

The Effect of Limb Loss on the Courtship and Mating Behavior of the Wolf Spider Pardosa milvina (Araneae: Lycosidae)

Limb loss is common in the wolf spider Pardosa milvina, appearing in nearly one third of adult males but occurring less frequently among adult females and juveniles. Since males wave their first pair of legs during courtship displays, the reproductive consequences of limb loss may be significant. We measured the courtship and mating effects of the loss of one, two, or four legs among adult male P. milvina. Missing one or two legs did not significantly reduce a male's ability to mate, but missing four legs was detrimental to mating success, reduced both courtship intensity and copulation duration, and increased cannibalism frequency. Results suggest behavioral flexibility in compensating for limited leg loss and a defensive function of the anteriormost legs to thwart female cannibalism attempts.     

Calling song and selective phonotaxis in the field crickets,Gryllus firmus andG. pennsylvanicus (Orthoptera: Gryllidae)

The field cricket species, Gryllus firmusand G. pennsylvanicus,occur in a mosaic hybrid zone that roughly parallels the eastern slope of the Appalachian mountains in the northeastern United States. It is important to know what role, if any, the calling song plays in mate choice in sympatric and allopatric populations. In this report, we present results on the variability of calling song properties along transects across this hybrid zone. We also present the results of experiments on phonotactic selectivity of females from an allopatric population of G. firmus.The male calling song of allopatric G. firmuswas significantly slower in temporal rhythm (i. e., chirp and pulse repetition rates) and lower in pitch (i.e., dominant frequency) than that of allopatric G. pennsylvanicus.Calling song properties of males recorded in the hybrid zone varied considerably in temporal and spectral properties. In two-stimulus (choice) phonotaxis experiments, allopatric females of G. firmuspreferred synthetic calling songs with conspecific pulse repetition rates over songs that had lower and higher pulse rates. This preference persisted even when the sound pressure levels of alternative stimuli were unequal. Therefore, allopatric females of G. firmuscan discriminate between conspecific and heterospecific calling songs. Whether or not this same selectivity is present in sympatric populations remains unclear. Investigations of phonotactic selectivity in other allopatric and sympatric populations of both species are currently under way.     

Rhesus macaque copulation calls: Re-evaluating the “honest signal” hypothesis

Male rhesus macaques sometimes give loud calls while thrusting or dismounting during multi-mount copulations.Hauser (1993) has proposed that these calls (1) impose a cost (increased risk of aggression) on calling males, and (2) increase callers' copulation frequencies, supporting the hypothesis that calls function as honest signals (handicaps) that females use to evaluate male quality during mate choice. This hypothesis was re-examined using data collected at Cayo Santiago, Puerto Rico on 40 focal females and their 56 observed copulatory partners. Although attacks by males against copulating pairs were frequent, they were usually directed only against the female of the pair. Males that called were no more likely than silent males to suffer male escalated attack during or immediately following mount series. Male-female dyads in which the male called during copulation were significantly more likely than non-calling dyads to complete the most copulations observed for any given female. Males that called at least once were significantly more likely than non-calling males to complete at least one copulation with a peri-ovulatory female. A log-linear model revealed that male rank and calling were both associated with likelihood of experiencing at least one peri-ovulatory copulation. However, calling was not associated with reception of demonstrated female mate choice behaviors. Controlling for dominance rank, callers did not experience more female proximity maintenance than non-callers. Nor were callers' hip-grasps refused less frequently than non-callers' hip-grasps. These results cast doubt on the hypothesis that rhesus macaque copulation calls are costly, honest indicators of intrinsic male quality. A contrasting alternative hypothesis, that a male's copulatory calls advertise relative immunity from attacks against his copulatory partners, was not supported either. Thus, the function of rhesus macaque copulatory calls remains unknown. The unusually high rate of copulations amongHauser's (1993) subjects may explain the discrepancy in results, but it is unclear how high copulation rates would increase the cost of copulatory calling to males.     

Courtship behavior and discrimination between potential mates by maleDelia antiqua (Diptera: Anthomyiidae)

The repertoire of courtship behaviors of male onion maggots,Delia antiqua (Meigen), in a laboratory bioassay chamber, was analyzed by direct observation and by video recordings, in conjunction with a multichannel event recorder. Seven courtship behaviors were categorized: inspection from the substrate, aerial inspection, contact from the substrate, contact from the air, genital alignment, copulation, and male-male interaction. The frequency distribution of copulation bouts was best described by a Poisson distribution; peak mating activity occurred about 1 h into the bioassay. The duration in copulo, however, was extremely variable. On average, males spent 30 sin copulo (n=183); <30% of bouts were >50 s. The ability of males to discriminate between sexes, sexually immature and mature females, and between females ofD. antiqua and the cabbage maggot,Delia radicum (L.), was most pronounced in the elements of genital alignment and attempted copulation. The courtship and mating behavior inD. antiqua is consistent with a sequence that relies initially primarily on indiscriminate visual recognition of a potential mate, followed by species-and sex-specific semiochemical recognition upon contact.     

Mating Behavior of Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae): Potential for Outbreeding in a Predominantly Inbreeding Species

The mating behavior of the quasi-gregarious egg parasitoid Trissolcus basalis (Wollaston) was investigated under field conditions. Trissolcus basalis has female-biased sex ratios and is a protandrous species, with males emerging 1–2 days before females. Males competed aggressively for control of the egg mass, with one male assuming dominance and control of the egg mass, although changes in dominance occurred at least once on each egg mass observed. Typical mating behavior involved the dominant male mating his sisters immediately upon their emergence from the egg mass. These behaviors are characteristic of an inbreeding species that manifests local mate competition. However, several aspects of the mating behavior of T. basalis are inconsistent with that of an inbreeding species. Over 18% of emerging females were not mated by the dominant male upon emergence, 13% of females were not observed to be mated at all and may have left their natal site as virgins, 25% of females were mated multiple times and sometimes by multiple males, females remained near the natal site for up to several hours after emergence before emigrating, and males dispersed away from the natal site during female emergence. Trissolcus basalis may be a predominantly inbreeding species but its emergence and mating behavior suggest that low-frequency outbreeding is also likely to occur.     

拟环纹豹蛛雄蛛触肢上黑白相间毛饰物的功能

狼蛛科雄蛛附肢上多样化的饰装往往与求偶行为相偶联,这些特殊的饰装通常被认为是雌性选择的结果。拟环纹豹蛛Pardosa pseudoannulata,属狼蛛科豹蛛属,雄蛛触肢胫节密被白毛,跗舟密被黑毛,具有典型的性二型现象;同时,只有成熟的雄蛛才展现触肢黑白相间的毛饰物。推测拟环纹豹蛛雄蛛触肢这种黑白相间的毛饰物可能在物种识别中具重要作用。在室内我们拟通过涂抹操作对拟环纹豹蛛雄蛛触肢黑白相间毛饰物的功能进行分析。实验分为4组,分别是对照组(A组,雄蛛不做任何处理)、雄蛛触肢白色胫节全部涂成黑色(B组)、雄蛛触肢黑色跗舟全部涂成白色(C组)和雄蛛触肢的黑色跗舟被涂成黑色(D组),然后采用雌雄配对进行求偶交配行为测定。实验结果表明,B组雄蛛的交配成功率显著低于A、C和D组的雄蛛,而后3组雄蛛的交配成功率无显著差异。相反,B组雄蛛被雌蛛相食百分率显著高于其它3组。可见拟环纹豹蛛雄蛛触肢上黑白相间毛饰物,尤其是其胫节上的白色饰物在雌蛛种间识别中起重要作用。     

Inter- and intraspecific variation in nightly calling duration in field crickets,Gryllus integer andG. rubens (Orthoptera: Gryllidae)

The time that male field crickets spend calling was measured electronically in the laboratory to examine nightly calling duration from different species and populations. Male Gryllus integerfrom Davis, CA, and Las Cruces, NM, called approximately 7 h per 24 h, whereas male G. integerfrom San Antonio and Austin, TX, and Norman, OK, and male G. rubensfrom McAlester, OK, and Arkadelphia, AR, called approximately 3 h per 24 h. Variation in duration of calling is discussed in terms of the energetic costs of producing song and selection against calling by acoustically orienting parasites and predators. Duration of calling was also studied infield-collected male G. integer.Males were first observed in field populations and then collected. Those males observed calling in the field later called significantly more in the laboratory than males observed showing non-calling, satellite behavior. Flying G. integercollected under lights were intermediate in their calling duration to calling and satellite males. These data are discussed in terms of the heritability of nightly calling song duration infield crickets.     

Territorial and mating behavior ofXylocopa fimbriata F. andXylocopa gualanensis Cockerell from Costa Rica

The territorial and mating behavior of two Xylocopaspecies X. fimbriataF. and X. gualanensisCockerell from Costa Rica are described. Male territorial activity was common during February through April in the higher areas of a dry forest savanna. Both species maintained territories at the same location within hollows in the foliage of Ardesia revolutaH.B.K., a small evergreen tree which occurs commonly in the dry forest. Xylocopa fimbriatamaintained territories during early morning hours, whereas the territorial period for X. gualanensisoccurred during late afternoon. Males of both species infrequently marked territories. It is suggested that a secretion released from their mesosomal glands is wiped onto their legs during frequent leg-body and leg rubbing which occurs while males hover. The secretion is occasionally applied to marking points on vegetation by their secretion-contaminated legs. Males repeatedly marked select locations when females were near their territories regardless of whether females were searching nearby branches for nesting sites, gathering provisions, or passing through their areas. Some females oriented to and entered certain male territories. An example of female mate choice in selection of male territories is provided. Females flew into male territories from 2–4 cm down-wind of male scent-marked locations. As females approached these locations, males hovered downwind in close proximity to the females' approach path. As females hovered a few centimeters downwind of the scented focal point, males approached from downwind and mounted. The males behavior and the role of scent-marking in the reproductive behavior of lek polygyny is discussed.