Ovarian development of Agrilus planipennis: effects of age and mating status and influence on attraction to host volatiles

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp. (Oleaceae), in North America. This study investigated the timing of reproductive development in female beetles and the influence of female reproductive maturity on attraction to host volatiles. Based on dissections of females of increasing age, females with access to males for mating, and thus presumed mated, developed mature eggs only after 18–24 days. In contrast, female beetles reared without access to males, and thus unmated, did not develop mature eggs at any age. Chemical analysis of cuticular hydrocarbons detected the contact sex pheromone, 9‐methyl‐pentacosane, in cohorts of females which were 8–9 days old and older, supporting previous research that this compound signals sexual maturity to males. Results from field‐trapping bioassays demonstrated that stage of female reproductive maturity influenced their attraction to host volatiles: females caught on traps baited with foliar volatiles contained eggs and ovarioles that were significantly less developed than those on traps baited with bark sesquiterpenes. However, our results revealed that females with immature stages of ovarioles and undeveloped eggs, such as those observed in unmated females, were rarely ever caught on traps baited with either of the host volatile lures. Further research on host compounds attractive to immature females is critical for early detection and possible control of A. planipennis populations during the extended pre‐oviposition period.     

Comparative attraction of four different fiberglass traps to various age and sex classes of stable fly (Diptera: Muscidae) adults

An Alsynite cylinder trap and three different Williams cross-configuration traps with three adhesives were compared to determine their relative attraction to stable fly, Stomoxys calcitrans (L.), adults. Williams traps coated with Olson Sticky Stuff performed as well as Williams traps coated with Tack Trap, thus allowing fly samples collected with either adhesive to be compared. The cylinder trap captured fewer total flies, but more flies per cm2 than any of the Williams traps. Sex ratio of flies captured on the cylinder trap was 50:50, while the three Williams traps captured predominantly males. The cylinder trap captured a larger percentage of nulliparous, unmated females than did the other traps tested.     

Male mate choice in the chameleon grasshopper (Kosciuscola tristis)

In many species, males can increase their fitness by mating with the highest quality females. Female quality can be indicated by cues, such as body size, age and mating status. In the alpine grasshopper Kosciuscola tristis, males can be found riding on subadult females early in the season, and as the season progresses, males engage in fights over ovipositing females. These observations suggest that males may be competing for females that are either unmated (early season) or sperm‐depleted (late season). We thus hypothesised that male K. tristis may be choosy in relation to female mating status, and specifically, we predicted that males prefer females that are unmated. We conducted behavioural experiments in which males were given the choice of two females, one mated and one unmated. Contrary to our prediction, males did not mate preferentially with unmated females. However, copulation duration with unmated females was, on average, 24 times the length of copulation with mated females. While female K. tristis can reject mates, we did not observe any evidence of overt female choice during our trials. Females may gain additional benefits from mating multiply and may therefore not readily reject males. While our experiment cannot definitively disentangle female from male control over copulation duration, we suggest that males choose to invest more time in copula with unmated females, perhaps for paternity assurance, and that male mate assessment occurs during copulation rather than beforehand.     

Male-Biased Capture in Light Traps in <Emphasis Type="Italic">Spodoptera exigua</Emphasis> (Lepidoptera: Noctuidae): Results from the Studies of Reproductive Activities

Nocturnal insects show phototactic behavior. Interestingly, males are caught by light traps more often than females in many species. In the present study, the male-biased capture in light traps in the field was evaluated to test the hypothesis that male-biased capture was associated with the reproductive activities of Spodoptera exigua. During a 16-wk. period in 2011, a total of 5075 moths caught by light traps in the field revealed a significant male-biased capture. However, the sex ratio of the natural population was not significantly different from 1:1 from July to October 2011. The ratio of moths caught per hour by light traps showed that females were captured in the first half of the night, whereas the peak capture by light traps for males occurred in the second half of the night. Among the captured adults, the percentage of unmated females was significantly lower than that of the mated females and males. Experiments in the laboratory indicated that the time of activities for both sexes was consistent with the active patterns of oviposition and copulation. The percentage of flight-to-light of the unmated females was significantly lower than that of the mated females and males. Thus, the lower capture of the unmated females, which is associated with reduced positive phototactic responses of S. exigua, probably is one of the reasons resulting in the male-biased sex ratio in light traps.     

Evidence of female-produced sex pheromone of Adelphocoris suturalis (Hemiptera: Miridae): effect of age and time of day

After the reduction in the use of broad-spectrum insecticides, Adelphocoris suturalis (Hemiptera: Miridae) has become an important pest of transgenic cotton, Gossypium hirsutum L., in China. A. suturalis is a highly mobile insect, moving rapidly in and out of crop fields, and traps baited with sex pheromones may be useful in monitoring and controlling its numbers. However, little is currently known regarding the chemical communication based on sex pheromones by this species. To use the synthesized sex pheromone effectively as part of the integrated pest management, some fundamental biological parameters under which the pheromone is produced must be understood. In this study, attractiveness of adult females or males of A. suturalis to conspecific individuals was examined by Y-tube bioassay; we also investigated the female sexually mature age and circadian rhythm of male attraction to females of A. suturalis in the field in 2008 and 2010. Y-tube bioassay results indicated that only males were attracted to odors from sexually mature virgin females. Two-year field trapping experiments showed that 4-18-d-old virgin females effectively attracted males, and males were attracted to virgin females during the scotophase, with a peak between 1900 and 2300 hours. These results improve our understanding of the sexual communication behavior of A. suturalis and provide evidence of female-produced sex pheromone in this species.     

Response of both sexes of Trichoplusia ni (Lepidoptera: Noctuidae) to virgin females and to synthetic pheromone

Abstract. 1. Male and female Trichoplusia ni were caught at three locations in California in 1974 and 1975, in traps baited with virgin female T. ni or with synthetic female pheromone.
2. 71% of the females were captured between 20.00 and 21.00 hours; only 22% of the males.
3. Both mated and unmated females were trapped.
4. Comparisons of live trap vs. dead trap catches suggest that females are responding to the virgin females (or synthetic pheromone) and not to a combination of stimuli from the first trapped males plus female pheromone.     

Mating behavior of an aphidophagous ladybird beetle,Propylea dissecta （Mulsant）

Abstract The mating behavior of Propylea dissecta (Mulsant) was investigated in detail. Protandry was evident, as males mature earlier than females. Predicted age of sexual maturation of male and female ladybirds was 7.12 and 9.33 days, respectively. Males performed courtship in six steps, viz. approach, watch, examine, embrace, mount and attempt. Embrace is possibly an appeasement act, while examine serves to recognize mate. Chemical signals initiate male attraction toward females. Visual and tactile cues appear to secondarily help in mate recognition. Mating lasted longest (275.40±12.23 min) when it occurred between unmated individuals. It was much shorter (176.60±5.60 min) when prior mated individuals copulated. There was a significant decrease in mating durations when adults were subjected to five successive matings. Fecundity and percent egg viability increased significantly with increase in the number of matings.     

Female assessment of male functional fertility during mate choice in a promiscuous fish

Sexual selection should favour females that can assess the functional fertility of available sexual partners and avoid mating with recently mated, sperm‐depleted males. Our current understanding of the sensory mechanism(s) underlying female assessment of males based on their functional fertility and avoidance of sperm‐depleted males is incomplete. Female Trinidadian guppies (Poecilia reticulata) are known to avoid mating with males that they had previously observed mating with other females. Here, we investigated experimentally the proximate sensory cues that they use to distinguish between paired size‐ and colour‐matched mated and unmated males in the absence of visual public information on their prior mating histories. When only water‐borne chemical cues from the males were available, females avoided the previously mated male and preferred the unmated one, but they chose randomly when only male visual cues (and no chemical cues) were available. They also preferred unmated over mated males when freely swimming with them in a more sensorially complex environment with multiple male cues (i.e., visual, chemical and mechanical cues) concurrently available. Females exhibited no preference for either stimulus males when both were unmated, irrespectively of the sensory environment. These novel results suggest that, in the absence of prior visual public information on the recent mating histories of males, female guppies use olfactory cues putatively emitted by mated males to avoid mating with them. The source and nature of the implicated olfactory cues and the fitness benefits gained by female guppies in sexually preferring males that have not recently mated remain unknown and warrant further research.     

Male Mating Success in the Presence of a Conspecific Opponent in a Madagascar Hissing Cockroach,Gromphadorhina portentosa (Dictyoptera: Blaberidae)

The influence of a conspecific competitor on male mating behavior was examined in a Madagascar hissing cockroach, Gromphadorhina portentosa. Previous studies have suggested that both male-male competition and female discrimination during courtship interactions may influence male mating success. Familiar pairs of males with a known social association were placed in an arena with a single virgin female and observed. As expected, subordinate males mated significantly less often than their dominant opponents. In pairs in which one male mated, dominant individuals limited the access of subordinates to females. Dominant males displayed an increased frequency and duration of interaction with the female. However, in pairs where both males remained unmated, the mating behavior of dominant and subordinate males did not differ significantly. As interactions progressed, as in the case of males that remained unmated, subordinate males gained increased access to the female. Mated males tended to be larger than their opponent although within a rank, males that mated were no larger than those that remained unmated. These results are discussed in light of the possible roles of male-male competition and female discrimination during courtship interactions.     

Monitoring grape berry moth (Paralobesia viteana: Lepidoptera) in commercial vineyards using a host plant based synthetic lure

For some Lepidopteran pests, such as the grape berry moth Paralobesia viteana (Clemens), poor correlation between males captured in traps baited with sex pheromone and oviposition activities of female moths has called into question the value of pheromone-based monitoring for these species. As an alternative, we compared the capture of female and male grape berry moth in panel traps baited with synthetic host volatiles with captures of males in pheromone-baited wing traps over two growing seasons in two blocks of grapes in a commercial vineyard in central New York. Lures formulated in hexane to release either 7-component or 13-component host volatile blends captured significantly more male and female grape berry moth on panel traps compared with the numbers captured on panel traps with hexane-only lures. For both sexes over both years, the same or more moths were captured in panel traps along the forest edge compared with the vineyard edge early in the season but this pattern was reversed by mid-season. Male moths captured in pheromone-baited wing traps also displayed this temporal shift in location. There was a significant positive correlation between captured males and females on panel traps although not between females captured on panel traps and males captured in pheromone-baited traps for both years suggesting pheromone traps do not accurately reflect either female or male activity. Male moths captured in pheromone traps indicated a large peak early in each season corresponding to first flight followed by lower and variable numbers that did not clearly indicate second and third flights. Panel trap data, combining males and females, indicated three distinct flights, with some overlap between the second and third flights. Peak numbers of moths captured on panel traps matched well with predictions of a temperature-based phenology model, especially in 2008. Although effective, panel traps baited with synthetic host lures were time consuming to deploy and maintain and captured relatively few moths making them impractical, in the current design, for commercial purposes.     

Female mating status affects male mating tactic expression in the wolf spider Rabidosa punctulata

Males and females have conflicting interests on the frequency and outcomes of mating interactions. Males maximize their fitness by mating with as many females as possible, whereas choosy females often reduce receptivity following copulation. Alternative male mating tactics can be adaptive in their expression to a variety of mating contexts, including interactions with a relatively unreceptive mated female. Male Rabidosa punctulata wolf spiders can adopt distinctive mating tactics when interacting with a female, a complex courtship display, and/or a more coercive direct mount tactic that often involves grappling with females for copulation. In this study, we set up female mating treatments with initial trials and then paired mated and unmated females with males to observe both female remating frequencies and the male mating tactics used during the interactions. Males adopted different mating tactics depending on the mating status of the female they were paired with. Males were more likely to adopt a direct mount tactic with already-mated females and courtship with unmated females. Already-mated females were considerably less receptive to males during experimental trials, although they did remate 34% of the time, the majority of which were with males using a direct mount tactic. Whereas males adjusting to these contextual cues were able to gain more copulations, the observation of multiple mating in female R. punctulata introduces the potential for sperm competition. We discuss this sexual conflict in terms of the fitness consequences of these mating outcomes for both males and females.     

Enhanced attraction of Plutella xylostella (Lepidoptera: Plutellidae) to pheromone-baited traps with the addition of green leaf volatiles

Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is one of the most serious pests of Brassicaceae crops worldwide. Electrophysiological and behavioral responses of P. xylostella to green leaf volatiles (GLVs) alone or together with its female sex pheromone were investigated in laboratory and field. GLVs 1-hexanol and (Z)-3-hexen-1-ol elicited strong electroantennographic responses from unmated male and female P. xylostella, whereas (Z)-3-hexenyl acetate only produced a relatively weak response. The behavioral responses of unmated moths to GLVs were further tested in Y-tube olfactometer experiments. (E)-2-Hexenal, (Z)-3-hexen-1-ol, and (Z)-3-hexenyl acetate induced attraction of males, reaching up to 50%, significantly higher than the response to the unbaited control arm. In field experiments conducted in 2008 and 2009, significantly more moths were captured in traps baited with synthetic sex pheromone with either (Z)-3-hexenyl acetate alone or a blend of (Z)-3-hexenyl acetate, (Z)-3-hexen-1-ol, and (E)-2-hexenal compared with sex pheromone alone and other blend mixtures. These results demonstrated that GLVs could be used to enhance the attraction of P. xylostella males to sex pheromone-baited traps.     

Effects of gender and mating status on self-directed dispersal by the whitefly parasitoid Eretmocerus eremicus

1. The impacts of gender and mating on short‐range (< 10 km) dispersal by the whitefly parasitoid Eretmocerus eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae) were examined. A fluorescent dust‐marking technique was also tested. 2. In a vertical flight chamber, female flight duration was significantly longer than that of males, and unmated parasitoids flew for longer than mated parasitoids. The mean flight durations were: unmated females 34 min, mated females 10 min, unmated males 7 min, mated males < 1 min. 3. The dispersal behaviour of E. eremicus was investigated in the field using fluorescent dust. Before doing so, it was determined in the laboratory that this dust did not affect flight behaviour, was retained over the length of the experiments, and allowed large samples to be processed quickly and inexpensively. 4. In the field, traps were placed along annuli at 3, 5, 7, and 10 m from release points. Eighty‐seven per cent of the 4153 parasitoids captured were males. Sex ratios were near parity on release. 5. The difference in dispersal characteristics between males and females may be resource based, suggesting that certain requirements were met within the field plots for males that were not met for females. 6. Locally, males dispersed in a manner consistent with a simple diffusion model while females engaged in wind‐directed flight soon after leaving release sites. The fact that the genders exhibited dissimilar dispersal characteristics, supports the claim that insect flight, even by small species, can be self‐directed.     

Spatial distribution and population composition of the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar, and its implications for social organization

Through a 16-mo mark-recapture trap study, I examined aspects of spatial distribution and population composition in the brown mouse lemur, Microcebus rufus, a 42 g nocturnal strepsirhine. The study took place in the rainforest of Ranomafana National Park in southeastern Madagascar. Sherman live traps were set monthly for a variable number of nights in a quasi-grid 50 m apart. Captured individuals were marked for future identification and released at site of capture. More males than females were captured overall (102 versus 72) and at 83% of trap sites. Trap sex ratio fluctuated significantly over the course of the study. It was particularly male-biased between June and August (3.9:1), when more previously uncaptured males than females (14 versus 6) entered the trap population. Some of these males remained in the trap population. Although the average number of individuals captured was not significantly different between the first four and last four months of the study, the composition of the population changed. The female population, however, changed less: 28.9% of all females captured in the first four months of the study were recaptured in the last four months, compared to 9.7% of males. It is suggested that the pattern of appearance of new individuals and disappearance of others, both predominantly male, may indicate migratory activity. Furthermore, an average of eight individuals were captured at each trap site (approximately 70% of traps captured more than five), suggesting a high degree of spatial overlap. The average number of male and female individuals captured in each trap (5.5 males versus 2.5 females), the average number of trap sites at which males and females were captured (3.6 versus 2.4), and the average number of captures for males and females (9.8 versus 5.7) all differed significantly between the sexes.     

水稻二化螟的交配行为

在室内条件下,对水稻二化螟Chilo suppressalis的交配行为及能力进行了研究.结果表明：大多数二化螟雌蛾一生只交配一次,平均0.92次;而雄蛾具有多次交配能力,最多达4次,平均2.72次.二化螟雌蛾的日龄影响其交配率、交配起始时间和持续时间,随二化螟雌蛾日龄的增加,其交配率逐渐下降,交配起始时间逐渐提前,而交配持续时间逐渐上升.相反,二化螟雄蛾日龄对其交配率、交配起始时间和持续时间没有明显影响.交配日龄对二化螟雌蛾的生殖力也存在显著影响,随着二化螟雌蛾交配日龄的增加,雌蛾产卵量下降,卵孵化率降低,产卵期缩短,它们都与雌蛾交配日龄存在显著的负相关;而雌蛾产卵前期和雌蛾寿命随雌蛾交配日龄的增加而延长,与雌蛾交配日龄存在显著的正相关.但二化螟雄蛾交配日龄对雌蛾的生殖力没有明显影响,二化螟雄蛾一生都具有较强的交配繁殖能力.同时,不同交配史的雄蛾与雌蛾交配,对雌蛾的生殖力也没有显著影响.表明二化螟的交配活动是由雌蛾主导控制的.最后,对这些结果在二化螟性信息素防治中应用的可行性进行了探讨.在应用性信息素控制二化螟的实践中,可以在两方面取得实效,一是性信息素可以阻碍雌雄之间正常交配,降低交配率;二是可以推迟二化螟雌虫的交配,使其产卵量和卵孵化率降低.     

Short-term, postcopulatory changes in receptive and proceptive behavior in the female syrian hamster (Mesocricetus auratus)

The interactions between male and female hamsters were recorded in terms of proximity (approaching, leaving, and following by each member of the pair). The time spent sniffing the partner was also recorded. Mated and unmated females were tested three times on the day of estrus and once on the day following estrus. As expected, receptivity declined rapidly in mated but not unmated females. None of the proximity measures changed during estrus in the unmated females. However, female approaching (Ap% ≈ female approaches as percentage of all approaches) decreased 1–3 hr after mating and was associated with a decline in a number of measures of female proceptive behavior. Female leaving (L% = female leaves as percentage of all leaves) did not change. In unmated females Ap% has decreased and L% has increased by the day after estrus (Day 2 of the estrus cycle). In mated females the decrease in Ap% is accelerated (occurring within the 3 hr after mating) and precedes a change in L% which has occurred by the day after estrus (Day 1 of pregnancy). Thus, mating brings about not only a decrease in receptivity, as has been shown for several species, but also a change in female proceptive behavior and in her stimulus value to the male.     

Sexual Selection Under Scramble Competition: Mate Location and Mate Choice in the Eucalypt Leaf Beetle Chrysophtharta agricola (Chapuis) in the Field

For males of many species, the number of offspring sired can depend on the number of females mated. While pre- and postcopulatory choice by females can affect the outcome of potential mate encounters, mate location is a necessary prerequisite to any possible courtship and subsequent mating. Mate location of Chrysophtharta agricola in the field was examined using sticky traps baited with sexually receptive conspecific beetles. More beetles were caught on traps baited with conspecific beetles of either sex than on control traps that contained foliage only. Furthermore, 94% of beetles captured on control traps were males, indicating that the mating system of Chrysophtharta agricola can be labeled prolonged searching scramble competition polyandry, in which receptive females are evenly dispersed spatially and temporally, and males search competitively for them. Operational sex ratios were 1:1 throughout the season. By sampling paired and unpaired beetles in the field, we found that beetles generally did not select mates based on body size. Furthermore, neither sex mated preferentially with partners that were uninfected by parasitic mites or with beetles of the same generation. In the absence of postcopulatory female choice, the ability of males to locate females may therefore be the most important trait in determining male mating success.     

The cause of correlations between nightly numbers of male and female barking treefrogs (Hyla gratiosa) attending choruses

The number of males displaying in a lek or chorus each day isoften positively correlated with the number of females visitingor mating in the aggregation. I tested hypotheses that mightexplain such correlations in a study of the barking treefrog(Hyla gratiosa). Experimental reduction of the number of callingmales did not reduce female visitation, ruling out the hypothesisthat such correlations are owing to female preference for, orpassive attraction to, larger choruses. Separate regressionof the numbers of males and females on 13 environmental variablesexplained 45–74% of the variance in the nightly numbersof males and females. Partial regression coefficients for mostof the 13 variables were not significantly different betweenthe sexes, and the relative importance of variables in explainingvariation in the numbers of individuals was similar for bothsexes. These results support the hypothesis that positive correlationsbetween nightly numbers of males and females are owing to asimilar response by both sexes to the same environmental variables.Thus, it appears that the intense sounds emanating from chorusesof H. gratiosa do not function in long-range communication andmay instead be an epiphenomenon of intense, short-range vocalcompetition for females.     

Experimental confirmation of the polygyny threshold model for red-winged blackbirds

The polygyny threshold model assumes that polygynous mating is costly to females and proposes that females pay the cost of polygyny only when compensated by obtaining a superior territory or male. We present, to the authors' knowledge, the first experimental field test to demonstrate that females trade mating status against territory quality as proposed by this hypothesis. Previous work has shown that female red-winged blackbirds (Agelaius phoeniceus) in Ontario prefer settling with unmated males and that this preference is adaptive because polygynous mating status lowers female reproductive success. Other evidence suggests that nesting over water increases the reproductive success of female red-winged blackbirds. Here we describe an experiment in which females were given choices between two adjacent territories, one owned by an unmated male without any over-water nesting sites and the other by an already-mated male with over-water sites. Females overwhelmingly preferred the already-mated males, demonstrating that superior territory quality can reverse preferences based on mating status and supporting the polygyny threshold model as the explanation for polygyny in this population.     

Mating system of Bracon hebetor (Hymenoptera: Braconidae)

Abstract.

• 1 We report on the mating system of a field population of the parasitic wasp, Bracon hebetor, on a corn pile infested by the Indian meal moth, Plodia interpunctella. We demonstrate that the mating system is based upon male scramble competition polygyny with male aggregations on high places on the corn.
• 2 The sex ratio among adults was greater than 80% males on the surface of the corn, whereas below the surface the sex ratio was less than 45%. Males actively courted females on the surface, but there were no aggressive interactions among males during courtship or mating.
• 3 Approximately 20% of the females found on the surface of the corn had no sperm in their spermathecae, regardless of age, but the numbers of unmated females decreased later during the day.
• 4 In laboratory studies we showed that females from this population oviposit a female biassed sex ratio, and that only 14% of females were mated before dispersing from their place of emergence.
• 5 Thus sib-mating is unlikely in this gregarious parasitoid. This outcrossing mating system probably arose because of severe inbreeding depression that B.hebetor suffers via a sex locus: diploids that are heterozygous at the sex locus develop into females, but homozygous diploids are male and are generally inviable. The female biassed sex ratio may have evolved in B. hebetor in response to males being the more expensive sex, females dispersing more frequently from the population than males, or a fraction of females remaining unmated in the population.