Diel patterns of reproductive activities in the tomato fruit fly, Neoceratitis cyanescens

We describe the diurnal temporal and spatial patterns of reproductive activities (mating and ovipositing) of adult tomato fruit flies, Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae), under laboratory, field‐cage and field conditions. The distribution pattern of flies in the different habitats (host and non‐host plants) showed temporal, physiological and sexual differences. Mature females were observed to frequent host plants preferentially, particularly in the late afternoon. By contrast, immature females preferred to rest on non‐host plants throughout the day. Males frequented mainly non‐host plants but some were observed on host fruits in the morning. Mating activity took place preferentially on non‐host plants, in the morning. In laboratory cages, females showed a strong daily propensity to engage in mating behaviour; the mean percentage of mating females was 88 ± 5%. Time allotted to this activity (4 h 52 min ± 1 h 23 min in laboratory cages and at least 3 h for the mating pairs observed in the field) appeared considerable compared to the time required to satisfy feeding or oviposition activities. Except for a few ovipositing females observed in the morning, oviposition activities occurred mainly in the late afternoon.     

Mating status regulates post‐mating refractory period in Striacosta albicosta females

In polyandrous insect species, males may transfer substances to reduce sperm competition by affecting female sexual receptivity. In this study, we determined the incidence of polyandry in females of Western bean cutworm (WBC), Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), and investigated the influence of both previous female and male mating history on the duration of mating, the female refractory period, and subsequent calling behavior of females under controlled laboratory conditions. The mating status of WBC males influenced mating duration, with copulations involving previously mated males taking longer, possibly related to the time required to produce an ejaculate. The duration of the female refractory period and the onset time of recalling during the scotophase were both affected by female mating history, but not by that of the males. Females had a shorter refractory period and resumed calling activity earlier after their second and third matings than after their first mating. The earlier onset of calling by previously mated females could reduce competition with virgin females and their shorter refractory period could explain the high incidence of polyandry observed in nature.     

Divergence in mate finding behavior between two subspecies of the meadow grasshopperChorthippus parallelus (Orthoptera: Acrididae)

Two parapatric subspecies of the grasshopper Chorthippus parallelusform a hybrid zone in the Pyrenees. Partial assortative mating between subspecies must result from differences in elements of the sequence of behaviors that leads to mating. It was already known that the subspecies differ in the structure of the acoustic mating signal produced by males and in the amount of song produced under laboratory conditions. Here we investigate whether any differences exist in male mating strategies in the field, concentrating on the prediction that male C. p. erythropussing less and compensate for this by active searching (males divide their time between singing and moving in search of females). Results of field observations show that the two subspecies do in fact allocate their time differently. C. p. erythropusmales spend almost twice as much time moving around the habitat as C. p. parallelusmales. Furthermore, C. p. parallelusmales divide their time into long bouts of continuous singing alternating with periods of movement. C. p. erythropusmales, on the other hand, sing in short bursts interspersed with movement. The possible reasons for this divergence in male mating behavior and its consequences are discussed.     

Body size and mating success inDrosophila willistoni are uncorrelated under laboratory conditions

Mating activity and wing length were investigated in the F₁ progeny ofDrosophila willistoni females collected in the field to examine any possible relationship between body size and mating success. The flies were observed in a mating chamber under laboratory conditions. No significant differences in wing length were observed between copulating and noncopulating flies, and there was no significant correlation between wing length and copulation latency for both males and females. These results therefore suggest that the commonly accepted view that large body size is positively correlated with mating success inDrosophila does not always hold true. The results support the view that the extent of environmentally induced variation in body size may be an important factor in determining whether an association between body size and mating success is observed inDrosophila species.     

Effect of mating period and time‐of‐day for bloodmeal on rearing of Asian tiger mosquito (Aedes albopictus) in laboratory conditions

Colonization and maintenance of mosquitoes in the laboratory is required to study physiology, ecology, and behavior of mosquitoes and interactions between mosquito and pathogens. Artificial blood feeding systems have been widely used to maintain the laboratory colony of Aedes albopictus. In this study, we investigated the effects of mating period (1, 3, 6, and 10 days) and time‐of‐day for bloodmeal (08:00, 13:00, and 18:00) in the use of an artificial feeding system on blood‐feeding rate, female fecundity, egg hatching rate, and developmental time of the Asian tiger mosquito, A. albopictus. Younger females mated for three or fewer days reproduced more eggs compared to those of oldest females mated for ten days. Similar to the result for eggs laid, the mean egg‐hatching rate was significantly higher from the offspring of younger females than from those of older females. However, mating period and time‐of‐day for bloodmeal had no effect on the blood feeding rate and developmental time. Taken together, we suggest that three‐day mating with bloodmeal at 18:00 is optimal for maintaining colonies of A. albopictus in laboratory conditions.     

Effects of caffeine on mating behavior and sperm precedence in Tribolium castaneum

Biogenic amines such as dopamine are physiologically neuroactive substances that affect behavioral and physiological traits in invertebrates, and it has long been known that these substances affect mating behavior in insects. Caffeine is a dopamine activator and thus enhances dopamine receptor activity. However, the effects of caffeine intake on insect mating behavior have been largely unexplored. Therefore, we examined the effect of caffeine on mating behavior in the red flour beetle Tribolium castaneum. Caffeine, which activates dopamine, affected the mating behavior of T. castaneum males. Males who orally ingested caffeine courted faster than males who did not, resulting in faster mounting of females and less time to a male's external aedeagus protrusion. However, the present results showed no difference in sperm precedence measured as a P2 value between males fed caffeine and males not fed caffeine. We discuss the effects of caffeine on insect mating and the possibility that caffeine consumption may cause males to mate with more females in the laboratory.     

Variation in mating propensity and fertility in isofemale strains of Drosophila ananassae

Mating propensity and fertility were studied in five laboratory strains of Drosophila ananassae which were established from single females collected from different geographical localities. The results show statistically significant variation among different isofemale lines with respect to mating propensity and fertility. The strains showing greater sexual activity produce more progeny. Thus, there is a positive correlation between mating activity and fertility in D. ananassae. The comparison of mating frequencies of strains and their hybrids reveals the existence of heterosis and reciprocal effects. The data suggest that the males are more subject to intrasexual selection.     

Emergence rhythms and protandry in relation to daily patterns of locomotor activity inTrichogramma species

Summary In insect parasitoids, the mating structure of the population depends on the emergence pattern of adults and on their behaviour after emergence. In order to study some aspects of these characteristics in four species of egg parasitoid of the genusTrichogramma, laboratory experiments using automatic video analysis are performed. Adult emergence is concentrated in the morning, with an earlier time for males. The variability of the time of emergence is under genetic control. The relationships between the emergence pattern and the locomotor activity are considered by measuring individually: first, the delay between the emergence and the first locomotion which is significantly greater in females than in males and, second, the activity of newly emerged males, which is maximum at the time of the emergence of females. The locomotor activity is influenced by mating; mated females are much more active than virgin ones, mated males are less active than virgin ones. The adaptive values of the rhythmicity of emergence and of protandry are discussed together with their relationship with the patterns of locomotor activity. The results are also considered with respect to mating strategies in insect parasitoids; they actually support the hypothesis of mating occurring principally among individuals native to the same host patch inTrichogramma species.     

Sexual selection without sexual dimorphism: Bateman gradients in a simultaneous hermaphrodite

One of the most general patterns in sexual selection is stronger selection on mating activity in males than in females. This asymmetry is thought to result from the higher energetic cost of producing one female compared to one male gamete (anisogamy). However, most studies focused on gonochoric species with strong sexual dimorphism, in which males and females are necessarily under different selection regimes. The question remains whether anisogamy alone would suffice to produce such differences. In simultaneous hermaphrodites one can compare sexual selection on the male and female functions in the absence of sexual dimorphism. Here we quantify sexual selection in the hermaphroditic freshwater snail Physa acuta under laboratory conditions. We combine exhaustive behavioral records of mating activity in mating groups and molecular paternity assignment to measure the mating success and reproductive success of 120 individuals. Our results validate the prediction of stronger selection to gain mating partners in the male than in the female function. Moreover, we did not detect cross‐sex effects on fitness, or correlations between male and female production of offspring over the course of our experiment. We conclude that with respect to sexual selection P. acuta is comparable to gonochorists, confirming that anisogamy is a sufficient explanation for the differences in sexual selection regimes between sexes.     

Male Lekking duration and Mating Benefits in a Lek-Forming Hawaiian Drosophila

Variation in lekking duration of males of a Hawaiian Drosophila, D. grimshawi, was examined in laboratory enclosures. The relationship between variation in male lekking activity and number of eggs laid by females, proportion of eggs hatching, and total offspring production was investigated. Females mating highly active males laid fewer eggs and thus had lower offspring production than females mating less active males, even though other studies have shown that D. grimshawi females prefer more active males as mates. These results are discussed in terms of conflict between males and females over mating benefits and in trade-offs faced by males between lekking duration and offspring production per mating. Testis mass was not related to lekking activity levels, but males with heavier testes produced more offspring per mating, suggesting that males may vary in other ways that correlate with possible direct fitness gains for females.     

Mating behaviour and parapatry in two species of Australian reptile tick

Summary Few quantitative studies have examined the ecological consequences of similarities and/or differences in mating behaviour of parapatric species. Reproductive interference occurs between several parapatric species of Australian reptile tick, due to similarities in their mating behaviour (Andrews et al. 1982a). Attempts to determine whether reproductive interference serves to maintain parapatry between Amblyomma limbatum and Aponomma hydrosauri have been hindered because of difficulties in providing conditions conducive to conspecific mating in Amb. limbatum. The present study examined whether off-host and/or onhost temperature influenced the subsequent mating behaviour (i.e. the proportion of females that mate and the time when mating occurs) of these two species. Irrespective of the temperature experienced by ticks prior to host attachment, specific on-host temperatures were needed to induce mating in Amb. limbatum (i.e. host cloacal temperatures >32° C prior to the time of peak mating activity). Significantly more Amb. limbatum females were mated and the time taken by females to mate decreased with increasing on-host temperatures. mating in Ap. hydrosauri occurred over a wider range of on-host temperatures and the time when mating occurred did not alter at different on-host temperatures. In addition, significantly more Ap. hydrosauri males moved and each male made more moves on hosts than did Amb. limbatum males. It is suggested that Ap. hydrosauri may in consequence have a competitive mating advantage over Amb. limbatum at a boundary. Similarities in mating behaviour, on the other hand, increase the probability of reproductive interference, hence reduce the reproductive fitness of colonizing females of both species. We propose that similarities and differences in mating behaviour could play a critical role in the maintenance of parapatric boundaries.     

Effect of irradiation on mating performance and mating ability in the West Indian sweetpotato weevil, Euscepes postfasciatus

The sterile insect technique (SIT) is widely used for suppressing or eradicating target pest insect populations. The effectiveness of SIT depends on the ability of released sterile males to mate with and inseminate wild females. Irradiation not only damages the reproductive cells but the somatic cells as well. The mating behavior of irradiated males may be altered over time due to the depressed metabolic activity brought about by sterilization. In this study, we evaluated the mating behavior (copulation behavior, mating performance, and ability of sperm transfer) of irradiated males in Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae) for 16 days after irradiation in the laboratory. The mating performance of males irradiated with a 150 Gy dose, as currently used in the SIT program in Okinawa prefecture for E. postfasciatus, decreased compared to that of control after day 7. As a result, we considered that irradiation had no major effect on male mating behavior for approximately 1 week after irradiation.     

Effects of high CO2 on mating success,mating duration,and sperm transfer in the West Indian sweet potato weevil,Euscepes postfasciatus

Most terrestrial animals live in natural atmospheric conditions, but some are also adapted to low oxygen (hypoxic) or high-carbon dioxide (hypercapnic) conditions, such as in social insect nests, soil, caves, wood, and decaying material. Although it is possible that individuals adapt their behaviour to the environmental condition of their habitats, mating behaviour under ecologically possible ranges of CO₂ has not been well studied. We compared walking activity, duration of mating behaviour, and sperm transfer ability in the West Indian sweet potato weevil, Euscepes postfasciatus Fairmaire (Coleoptera: Curculionidae), in high CO₂ (10 000 p.p.m.) vs. normal atmospheric conditions (laboratory air, ca. 800 p.p.m.). We found that high CO₂ enhanced walking activity and mounting frequency. Under such circumstances, we predicted that enhanced activities under a high-CO₂ environment would increase the risk of sperm competition, which induces an extended copulation period and an increase in sperm transfer. However, weevils shortened the mating period and did not alter their sperm transfer ability under high CO₂. These findings are, as far as we are aware, the first report of the effect of ecologically relevant high CO₂ on insect mating behaviour under mass-rearing conditions. The effect of ambient conditions on mating behaviour and sperm transfer is discussed in relation to the intensity of female refusal behaviour directed against males.     

Life cycle changes during 12 successive generations of laboratory colonisation of the leafroller Cnephasia jactatana (Walker) (Lepidoptera: Tortricidae) on artificial diet

Abstract

Close monitoring of the lepidopteran leafroller Cnephasia jactatana under laboratory colonisation revealed few distinct effects of successive rearing on artificial diet on the life cycle. The second laboratory generation had a prolonged development time and altered sex synchronism in pupation and eclosion patterns. Some deleterious changes were observed in later generations, including decreases in fertility, egg hatch and sperm motility, failure of mating adults to separate, and pupal and adult malformations. These changes were not adaptive, but were due to incompatibility with the general purpose diet (GPD) used; they were absent under sub-colonisation on a sheepnut-bean based diet (SBD). Success in the laboratory colonisation of C. jactatana is attributed to a random mating protocol, choice of environmental conditions representing the wild habitat, and a rapid rate of population growth.     

Difference in the time of mating activity between host-associated populations of the rice stem borer, Chilo suppressalis (Walker)

Mating activities of the rice stem borer, Chilo suppressalis, were compared between rice‐ and wateroat‐feeding populations, and two potential temporal factors that may act as reproductive barriers were examined. Seasonal data of the number of moths attracted to pheromone traps showed that the peak of emergence at the rice field was approximately 10 days earlier than that at the wateroat vegetation in the first flight season, although there was a broad overlap of emergence at the two locations. Both field observations and a laboratory experiment showed that moths from the rice field started mating earlier than those from the wateroat vegetation. However, whereas the difference was distinctive in the laboratory experiment, mating activity at the wateroat vegetation shifted significantly to an earlier time phase than that observed in the laboratory. Body size data showed that the male moths attracted to the pheromone traps at the wateroat vegetation were significantly larger than those at the rice field, suggesting that the traps at the two locations mainly attracted moths originating from different host plants. However, pheromone‐trapped males at the rice field were significantly larger than those reared from overwintering samples. These results support the idea that males from the wateroat vegetation migrate to the rice field. The differences in seasonal and temporal mating activity and their effects on development of reproductive isolation between host‐associated populations are discussed.     

Middle aged wasps mate through most of the year, without regard to body size, ovarian development and nestmateship: a laboratory study of the primitively eusocial wasp Ropalidia marginata

We studied the mating behaviour of the primi-tively eusocial wasp Ropalidia marginata and the factors that may influence sperm transfer. By introducing a male and a female R. marginata into ventilated transparent plastic boxes, we were able to observe mating behaviour, and it involved mounting and short or long conjugation of the wasps. Dissection of female wasps after the observation indicated that long conjugation is a good behavioural predictor of sperm transfer. This finding makes it possible to obtain mated females without dissecting them every time. We tested the effect of age, season, relatedness, body size and female’s ovarian status on mating. Under laboratory conditions, mating success declined rapidly below and above the ages 5–20 days. Within this age range mating success was significantly low in December compared to other months tested. There was no nestmate discrimination, and there was no influence of male and female body size or of the ovarian state of the female on the probability of sperm transfer.     

Swarming and mating activity of Anopheles gambiae mosquitoes in semi‐field enclosures

Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) is the major Afro‐tropical vector of malaria. Novel strategies proposed for the elimination and eradication of this mosquito vector are based on the use of genetic approaches, such as the sterile insect technique (SIT). These approaches rely on the ability of released males to mate with wild females, and depend on the application of effective protocols to assess the swarming and mating behaviours of laboratory‐reared insects prior to their release. The present study evaluated whether large semi‐field enclosures can be utilized to study the ability of males from a laboratory colony to respond to natural environmental stimuli and initiate normal mating behaviour. Laboratory‐reared males exhibited spatiotemporally consistent swarming behaviour within the study enclosures. Swarm initiation, peak and termination time closely tracked sunset. Comparable insemination rates were observed in females captured in copula in the semi‐field cages relative to females in small laboratory cages. Oviposition rates after blood feeding were also similar to those observed in laboratory settings. The data suggest that outdoor enclosures are suitable for studying swarming and mating in laboratory‐bred males in field‐like settings, providing an important reference for future studies aimed at assessing the comparative mating ability of strains for SIT and other vector control strategies.     

Laboratory adaptation reduces female mating resistance in the sweet potato weevil

Selection for genetic adaptation might occur whenever an animal colony is maintained in the laboratory. The laboratory adaptation of behavior such as foraging, dispersal ability, and mating competitiveness often causes difficulties in the maintenance of biological control agents and other beneficial organisms used in procedures such as the sterile insect technique (SIT). Sweet potato weevil, Cylas formicarius (Summers) (Coleoptera: Brentidae), is an important pest in sub‐tropical and tropical regions. An eradication program targeting C. formicarius using SIT was initiated in Japan with weevils being mass‐reared for 95 generations to obtain sufficient sterile males. The mass‐reared strain of C. formicarius exhibits weaker female resistance to male mating attempts compared with the wild strain. This could affect the success of SIT programs because mating persistence of mass‐reared males might be expected to decrease in response to weak female resistance. We show that high success of sperm transfer to mass‐reared females was due to weak female resistance to male mating attempts. However, the mating behavior of mass‐reared males did not change. In C. formicarius, the trait of male persistence to mate was not correlated with the female resistance traits. Our results suggest that mass‐rearing conditions do not have negative effects on the mating ability of the sterile males of this species, and thus that the current mass‐rearing procedures are suitable for production of sterile males for the weevil eradication program.     

The costs and benefits of multiple mating in a mostly monandrous wasp

The taxonomically widespread nature of polyandry remains a puzzle. Much of the empirical work regarding the costs and benefits of multiple mating to females has, for obvious reasons, relied on species that are already highly polyandrous. However, this makes it difficult to separate the processes that maintain the current level of polyandry from the processes that facilitate its expression and initiated its evolution. Here we consider the costs and benefits of polyandry in Nasonia vitripennis, a species of parasitoid wasp that is “mostly monandrous” in the wild, but which evolves polyandry under laboratory culture conditions. In a series of six experiments, we show that females gain a direct fecundity and longevity benefit from mating multiply with virgin males. Conversely, mating multiply with previously mated males actually results in a fecundity cost. Sexual harassment may also represent a significant cost of reproduction. Harassment was, however, only costly during oviposition, resulting in reduced fecundity, longevity, and disrupted sex allocation. Our results show that ecological changes, in our case associated with differences in the local mating structure in the laboratory can alter the costs and benefits of mating and harassment and potentially lead to shifts in mating patterns.     

Spring behavioral patterns of the apple blossom weevil

Individual pairs of overwintered adult apple blossom weevils, Anthonomus pomorum (L.), confined with apple twigs under different ambient temperatures in the laboratory and on apple trees in the field, were observed through day and night for their spring activities. Flight behavior in relation to ambient temperature was also investigated under laboratory conditions using flight stands. Both sexes displayed predominantly nocturnal behavior patterns in both the laboratory and the field. Feeding, crawling, and mating activities increased following sunset in the field or onset of scotophase in the laboratory while resting occurred most frequently during daylight hours. Results of the laboratory experiments showed that temperature affected significantly the activity patterns. The diel pattern of activities became less distinctive at higher temperatures (above 15°C), and total activities in crawling, feeding, and mating were suppressed significantly at lower temperatures (below 5°C). Over 97% of the test weevils initiated take-off response from flight stands at 20°C within the 30 min trial period; however, flight initiation rarely occurred at temperatures 12°C or below. Overall, results of the laboratory and field experiments indicate that A. pomorum is a remarkably cold-adapted insect with ability to crawl, feed, and mate at a few degrees above freezing, a physiological attribute necessary for the exploitation of early stages of apple bud development in the cold early spring.