Mate Finding Via a Trail Sex Pheromone by <Emphasis Type="Italic">Aphytis melinus</Emphasis> DeBach (Hymenoptera: Aphelinidae) Males

Finding mates is frequently problematic for parasitoid wasps. In some parasitoid species, males rely on volatile, airborne sex pheromones for locating mates, while in others they rely on contact, trail sex pheromones. This study sought to shed light on the mate finding mechanism of males of Aphytis melinus. Specifically, the goal was to determine whether A. melinus males use airborne or contact pheromones, or both, for locating mates. The study showed that A. melinus males rely on a contact, trail sex pheromone for locating mates: A. melinus males responded to substrate-borne cues left by virgin females, while they did not respond to airborne cues from virgin females. Specifically, males more frequently encountered virgin females when the females walked across an arena to a fixed encounter point compared to when they were manually placed at the encounter point, and spent greater than expected time on surfaces previously visited by virgin females compared to control surfaces not visited by females. In contrast, males did not respond to airborne cues from virgin females in an airflow olfactometer nor to traps baited with virgin females in the field, and spent similar lengths of time on surfaces visited by newly-mated or 24-h mated females versus control surfaces not visited by females. The main effect of the trail sex pheromone on the behavior of A. melinus males was to direct their search and, so, increase the likelihood of encountering mates. This effect apparently is not preceded by longer-range attraction of males via an airborne female sex pheromone. Overall, the results of this study support a hypothesis in which A. melinus males searching on substrates on which females may be present rely exclusively on a trail sex pheromone to locate mates.     

The nature and development of sex attractant specificity in cockroaches of the genus Periplaneta. I. Sexual dimorphism in the distribution of antennal sense organs in five species

Sexual dimorphism in the distribution of antennal sense organs is common among adults of the genus Periplaneta. In three out of the four strains of Periplaneta americana examined, adult males had more contact chemoreceptors than females. In the fourth strain of P. americana and in P. australasiae, P. brunnea, P. fuliginosa, and P. japonica, no statistically supportable sexual dimorphism of contact chemoreceptors was found. However, in all strains and species of Periplaneta examined, sexual dimorphism was found in the total number and/or density of olfactory sensilla. Male adults had nearly twice as many olfactory sensilla as female adults. These observations are consistent with the behavioral observation that males within the genus Periplaneta rely on the reception of an airborne pheromone for the initiation of courtship behavior. In P. americana, where sexual dimorphism was found in the contact chemoreceptors, contact stimuli release the full wing raising display and presentation in males during courtship.     

松墨天牛是否存在雌性接触信息素?

将松墨天牛MonochamusalternatusHope的身体不同部位切除之后的交配试验显示,分别剪去头部、鞘翅以及前胸部后仍然可以正常交配,用雄虫的腹部代替雌虫的腹部后,仍然能够引起雄虫的交配趋势动作,但不能完成真正交配,因此推测雌性接触信息素如果存在,主要集中在雌虫身体后半部,尤其是中后胸部位。但是冻死后的雌虫不再引起雄虫的交配行为,而且冻死的雌虫与活雌虫同时放入培养皿中,雄虫喜欢与活雌虫交配,不选择冻死的雌虫,因此推测视觉在其松墨天牛的交配过程中扮演着重要的角色,而接触性信息素有可能并不存在。将雄虫的触角分别从第5~6节和第1节剪去的试验结果显示,雄虫仍然可以很快地找到雌虫,发生交配行为。这有2种可能的解释一是雄虫不仅仅靠触角来感受雌虫的接触信息素,头部下颚须和下唇须上或者足上也有可以感受信息素的感受器;二是雌虫不存在接触信息素,雄虫通过视觉就可以找到对方,完成交配过程。浸泡致死的雌虫不再引起雄虫的交配行为,并且将正己烷和乙醚的浓缩液滴加在浸泡致死的雌虫以及玻璃棒和鹅卵石的生测试验结果显示,都没有引起雄虫的交配行为。这进一步说明,松墨天牛可能并不存在体表接触信息素。性成熟后的松墨天牛雌雄成虫是靠衰弱寄主的强烈的挥发性气味聚集到寄主树干上,在树干这个较为狭小的环境里,有可能是通过视觉找到配偶,完成交配过程。     

Nocturnal Calling Behavior in Mantids

Females of Mantis religiosa and Empusa pennata were video taped for several 24 h periods to determine if they showed behaviors associated with pheromone release. In the photophase the abdomen of both species was motionless and rested in continuous contact with the wings. However, at the beginning of the scotophase the females bent the abdomen ventrally so that the space between the abdomen and the wings increased significantly with respect to the daytime posture. Calling behavior (abdominal bending) was maintained throughout the 8 h scotophase and ended abruptly at lights on. Females of M. religiosa did not start calling until they were 30 days of age. Calling disappeared in mated females, but it reappeared two weeks later. Males stayed motionless in response to the odors emitted by other males or by noncalling females, but walked when a calling female was placed in the air flow. These observations suggest that female mantids bend their abdomens at night to release a sex pheromone. The adaptive function of nocturnal sex pheromone release in sexually cannibalistic species that rely strongly on visual cues for mating is discussed.     

Modeling mate-finding behavior of the swarming polychaete,Nereis succinea,with TangoInSilico,a scientific orkflow-based simulation system for sexual searching

Summary

Pheromones can be used as attractants for the opposite sex in many environments; however, little is known about the search strategies employed in responding to pheromones in the marine environment. The spawning behavior of males of the polychaete Nereis succinea is known to be triggered at close range by a high concentration (>～10^?7 M) of pheromone, cysteine glutathione disulfide (CSSG), released by females. Since CSSG also causes acceleration of swimming and increased turning, in addition to eliciting ejaculation, we proposed the hypothesis that these behaviors elicited by low concentrations of pheromone can be used by males to find females. The current study develops a computer simulation model of male and female N. succinea behavior for testing whether male responses to low concentrations of CSSG can facilitate finding females. Video recording of female swimming behavior in the field showed spontaneous loops, spirals, and circles that have been incorporated into the model. The scientific workflow paradigm within which the computer model has been developed also incorporates a data provenance system to enable systematic replay and testing of responses to individual parameters. Output of the model shows complex turning behavior leading to successful mating encounters at concentrations as low as 3×10^?9 M CSSG. Behavior resembling the output of the model was recorded in field observations. Application of the model in the future will be used to determine what pheromone concentrations produce significant increases in the probability of mating encounters.     

The role of 2,6-dichlorophenol as sex pheromone of the tropical horse tick Anocentor nitens (Acari: Ixodidae)

The objective of this study was to evaluate the role of2,6-dichlorophenol (2,6-DCP) as sex pheromone of Anocentornitens. Sex pheromones were extracted by submerging 150 females fed for 6 days in hexane (3 ml) for two hours and sonicating them for15 min. The extract was analyzed by GC-MS employing the Single Ion Monitoring (SIM) method. Identification of 2,6-DCP was based on the comparison of mass spectra with a computer search using the NIST library and by matching the mass spectrum of the peak at the retention time of 2,6-DCP from extract sand the synthetic product. In an olfactometer, males were released at 2.5cm from females, control rubber septa and impregnated rubber septa with increasing concentrations of 2,6-DCP (50, 500 and 5000 ng). A higher percentage of orientation and higher frequencies of angles between 0° and 10° were observed for males tested with females than with controls. Attraction of males to dummies impregnated with 2,6-DCP was observed with highest response (100%) at 50 ng. There was a gradual decrease of responsiveness of males with increasing concentration of 2,6-DCP (70 to 75%).This compound stimulated a behavior of mounting and ventral positioning ofA. nitens males at the lowest 2,6-DCP concentration where as dummies impregnated with 2,6-DCP higher than 50 ng concentration inhibited these behaviors. Therefore, we can conclude that 2,6-DCP can elicit the complete behavior sequence of orientation, location, mounting and ventral positioning behaviors and plays a role as an attractant and, as a mounting sex pheromone in A. nitens. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evolutionary trends in the male pheromone systems of arctiid moths: evidence from studies of courtship in Phragmatobia fuliginosa and Pyrrharctia isabella (Lepidoptera: Arctiidae)

Male Phragmatobia fuliginosa and Pyrrharctia Isabella evert tubular abdominal scent-organs (coremata: during courtship. The coremata secrete a pheromone that is derived from pyrrolizidine alkaloids (PAs) obtained during larval feeding. Field-collected males vary widely in the amount of pheromone they possess. The courtship behaviour of these species was studied to determine whether this variation among males serves as a basis for mate choice by females, in a wind-tunnel a male approaches a pheromone-releasing female from downwind with his coremata everted in flight. A female perceiving the pheromone responds by fluttering her wings and emitting a clicking sound. This response did not occur in all courtships, and successful copulation was not dependent on its occurrence. Males denied access as larvae to the PA-precursors of the corematal pheromone (PA-denicd males' mated as rapidly as males allowed access to pheromone precursor (PA-supplied males). Moreover, antennectomized females mated as rapidly as normal females. Comparative analyses of transitional probabilities indicated no differences among courtships involving ! I': PA-denicd males and normal females, (II) PA-supplied males and normal females, or antennectomized females and normal males of unspecified feeding history. Field observations of courtship interactions between laboratory-reared females and wild males indicated that males having little or no pheromone succeed in mating in a natural setting as do males having a relativelv large amount of pheromone. It is hypothesized that the failure of female Ph. fuliginosa and Py, Isabella to enforce the display of PA-derived pheromone is related to an cvolutionarv trend away from an ancestral larval host-range restricted to PA-containing plants toward the polyphagv shown by manv temperate and arctic arctiids in the lineage (subfamily Arctiinae: tribe Arctiini) to which Ph. fuliginosa and Py. Isabella belong. Parallels in other moth groups are cited to support the notion that a plesiomorphic courtship pheromone system could persist in a vestigial state, despite the loss of its adaptive raison dêtre.     

Evidence for male- and juvenile-specific contact pheromones of the common bed bug Cimex lectularius

Males and females of the common bed bug, Cimex lectularius L. (Heteroptera: Cimicidae), have been shown to produce and respond to an aggregation pheromone. We tested whether juvenile C. lectularius also produce and respond to aggregation pheromone, and whether the pheromone is perceived by contact chemoreception. In dual‐choice laboratory experiments, juveniles, but not males or females, preferred juvenile‐exposed paper discs to control discs. Unlike juveniles, males and females preferred male‐exposed paper discs to control discs. Neither juveniles, males, nor females preferred female‐exposed discs to control discs. When test stimuli were inaccessible, C. lectularius failed to show any preference. Male‐ and juvenile‐specific contact pheromones may have contrasting functions of marking shelters as safe refugia for development and growth (juveniles) or mate encounter (adults), but result in the same phenomenon, the aggregation of conspecifics.     

Calling Behavior in the Primitive Longhorned Beetle Prionus californicus Mots.

Many prionine species share morphological and behavioral traits commonly associated with production of volatile pheromones by females. Adults Prionus californicus Mots. are sexually dimorphic, males being smaller and having antennae that are much more strongly serrate than those of females. Females of this species produce a volatile pheromone that attracts males. We conducted studies characterizing calling behavior of P. californicus females. In these studies females typically lowered their heads and raised their abdomens while extending their ovipositors. The extended ovipositor was often flexed and the abdomen rhythmically contracted during these bouts which lasted up to 10 min. In some cases females everted a membranous, cylindrical sac from the dorsal surface of the ovipositor which was retracted before the ovipositor was withdrawn. This eversible sac has not reported for a cerambycid species, and is likely to be involved in production and/or release of pheromone.     

Electrophysiological and Behavioral Responses of Female Beet Armyworm Spodoptera exigua (Hübner) to the Conspecific Female Sex Pheromone

Electroantennogram (EAG) recordings showed that female Spodoptera exigua can detect their own sex pheromones (two single components and their mixture), displaying a similar dose–response pattern to that of males, although intensities of female responses were much less at all doses compared with males. Furthermore, the female calling behavior was inhibited and late-shifted by the presence of the female sex pheromone. When the pheromone components were presented, the calling female proportion in the peak calling period was significantly reduced and the calling peak time and calling termination time postponed, compared with controls. Although the calling behavior was inhibited, the pheromone titer of treated females was not different to the control, implying a reduced pheromone biosynthesis in the pheromone glands of treated moths. However, observations during the olfactometer experiments revealed that there were no obvious behavioral responses of females exposed to sex pheromone stimuli including whole gland extracts, 0.1, 1 or 10 μg binary pheromone mixtures.     

CHEMICAL COMMUNICATION IN HAWAIIAN DROSOPHILA

We are interested in elucidating the extent to which lekking Hawaiian Drosophila species have diverged from their continental counterparts, which engage in sexual behavior at communal food sources, with regard to the chemical communication systems that the flies employ. Accordingly, we have analyzed flies from three closely related Hawaiian Drosophila species in the adiastola subgroup. These species are of interest because the males engage in a unique behavior: while courting, they raise their abdomens over their heads and emit anal droplets. Analysis of the flies' behavior, the hydrocarbons in males' anal droplets, and males' cuticular hydrocarbons suggest that females' responses to males may be mediated by cuticular pheromones and/or pheromones in males' extruded droplets that enable the females to distinguish conspecific from heterospeciflc males. Conversely, perception of cuticular hydrocarbons from conspecific females enables D. adiastola males to distinguish females from a closely related species from conspecific females. On the basis of these observations, we suggest that the adiastola subgroup species are unique among drosophilids in that they utilize an anal droplet-mediated pheromone communication system, some or all components of which are species specific. However, the lekking Hawaiian Drosophila species are similar to D. melanogaster and related continental species in that the Hawaiian flies employ a cuticular pheromone communication system, some components of which are sex and species-specific.     

Calling behavior of the female german cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Virgin German cockroach females, Blattella germanica(L.), were observed, for the first time, to exhibit a characteristic calling behavior during which females emit a volatile sex pheromone. Under a photoperiod of 12L12D, the percentage of 7-day-old virgin females that exhibited this behavior peaked before the end of the scotophase in a similar pattern to the diel periodicity of mating. A clear relationship was evident between calling and stages of sexual receptivity during successive gonotrophic cycles. Females initiated calling 5–6 days after the imaginal molt, when their basal oocytes were 1.6 mm long. If not mated, females continued to exhibit bouts of calling during the next 3–4 days until 24 h before ovulation. Calling was completely suppressed by mating as well as the presence of an egg case in the genital atrium in both virgin and mated gravid females. We suggest that calling and the emission of a volatile sex pheromone serve to attract males from a distance as well as to potentiate responses to contact sex pheromone in aggregations.     

Responses of Second-Instar Male Nymphs of Four Mealybug Species (Hemiptera: Pseudococcidae) to Conspecific and Heterospecific Female Sex Pheromones

The response of the late second-instar male nymphs of the mealybug species (Hemiptera, Pseudococcidae), Planococcus citri (Risso), Planococcus ficus (Signoret), Pseudococcus cryptus Hempel Nipaecoccus viridis (Newstead), to their conspecific and heterospecific female pheromone was studied. Males that exhibited the typical appearance of late-second-instar nymphs were tested. The male behavior was monitored soon after their exposure to the tested female sex pheromone in glass Petri dish arenas. Male nymph behavior toward the pheromone source was characterized based on their aggregation on the disks in the arena. Males of all four tested mealybug species were attracted to their conspecific female pheromone. By contrast, almost no interceptions of male nymphs with disks impregnated with a heterospecific female pheromone were observed. The mode of attraction of each of male nymphs of P. ficus, among most of the tested individuals (>80%), to the conspecific female sex pheromone, (S)-lavandulyl senecioate and or (S)-lavandulyl isovalerate, was the same as the mode of attraction latter on as adult. We suggest that by being attracted to the conspecific pheromone these males may direct themselves to a suitable pupation site near conspecific non-sibling mature females, thus preventing inbreeding. The repellency of heterospecific sex pheromone to males that are looking for a pupation site suggests that the latter try to avoid close contact with heterospecific females.     

FUNCTIONAL ASPECTS OF DROSOPHILA COURTSHIP

1. The elements that make up the courtship behaviour of males and of females are briefly described. It is pointed out that some of the terms used, such as female ‘repelling’ behaviour, are misleading as they do not reflect the known functions of the behaviours. 2. Evidence has been presented for a number of distinct pheromones with different functions during courtship. These claims are critically examined as the evidence is incomplete and at times conflicting. It seems unlikely that any pheromones other than those acting over a very short distance are involved in courtship. There is sound evidence for an aphrodisiac pheromone produced by all females which stimulates male courtship. A pheromone, which may be the same one, is produced by males less than 12 h old, which also stimulates male courtship. No function is ascribed to this pheromone. Fertilized females either produce less aphrodisiac pheromone or they may, in addition, produce one that inhibits male courtship. Mature males may also produce an inhibitory pheromone. Females produce a contact pheromone which is species-specific and involved in sexual isolation. It is not at present clear whether this is different from the aphrodisiac pheromone. 3. There is considerable variability in the importance of vision in courtship. Many species will mate satisfactorily in the dark, suggesting that visual stimuli are not critical. Most species use vision to orient towards one another and for males to track and follow females. Even in light-independent species such as D. melanogaster, specific visual signals may be used in courtship although they are not obligatory. Thus the red eye of the male is a sexual signal for females. Conversely, some light-dependent species do not appear to make use of visual signals as a major factor in courtship. Some, however, do perform behaviours that are clearly visual and which may act to emphasize markings on wings, head or body. 4. The majority of Drosophila species perform courtship songs by vibrating one or both wings. The songs produced by males sexually stimulate the females. They are species specific and there is considerable indirect and some direct evidence that the songs are involved in sexual isolation. Males of many species produce two different songs during courtship and it is probable that one is concerned mainly with sexual stimulation and the other with species recognition. Females of certain species of Drosophila and Zaprionus also sing during courtship and these songs may aid species recognition by males. In addition males and unreceptive females perform ‘aggressive’ songs. 5. Almost all studies of Drosophila courtship have been made in very confined conditions in the laboratory. Interpretation of some of the results obtained in this way may require modification in the light of ecological research and observation of courtships under more natural conditions.     

Cytophysiological study of neurosecretory and pheromonal influences on sexual development in Ophryotrocha puerilis (Polychaeta,Dorvilleidae)

Summary

Prominent secretory nerve endings are found at the posterior margin of the supraesophageal ganglion in the protandric polychaete, Ophryotrocha puerilis. Solitary juveniles developing as primary males, and then as females, accumulate neurosecretory material in the nerve endings which thereby swell and become filled with granules. Females maintained in mass culture have similar terminals, whereas in secondary males (males which had been females before), these axon terminals are very small and contain no material. When such males are isolated, they accumulate neurosecretory material within the nerve endings and become females. When formerly isolated females are put together, their stores of neurosecretory material are rapidly discharged. Subsequently they lay egg masses and switch to the male state. These effects are mediated by a pheromone released during social contact of formerly isolated females. The complexity of the relationship between neurosecretory activity and sexual state is indicated by the situation in animals maintained in pairs, when both male and female partners have swollen nerve endings packed with secretory material.     

Use of bilateral information to determine the walking direction during orientation to a pheromone source in the silkmoth Bombyx mori

Odor source localization is an important animal behavior. Male moths locate mates by tracking sex pheromone emitted by conspecific females. During this type of behavior, males exhibit a combination of upwind surge and zigzagging flight. Similarly, the male walking moth Bombyx mori responds to transient pheromone exposure with a surge in movement, followed by sustained zigzagging walking. The initial surge direction is known to be influenced by the pheromone input pattern. Here, we identified the sensory input patterns that determine the initial walking direction of males. We first quantified the stimulus by measuring electroantennogram values, which were used as a reference for subsequent tests. We used a brief stimulus pulse to examine the relationship between sensory stimulus patterns and the turning direction of initial surge. We found that the difference in input timing and intensity between left and right antennae affected the walking direction, indicating that B. mori integrate bilateral pheromone information during orientation behavior. When we tested pheromone stimulation for longer periods, turning behavior was suppressed, which was induced by stimulus cessation. This study contributes toward understanding efficient strategies for odor-source localization that is utilized by walking insects.     

7‐methylheptacosane is a major component of the contact sex pheromone of the cerambycid beetle Neoclytus acuminatus acuminatus

Abstract Male Neoclytus acuminatus acuminatus (F.) (Coleoptera: Cerambycidae) attempt to mate with females only after touching them with their antennae, suggesting that mate recognition is mediated by contact pheromones in the cuticular wax layer of females. Consistent with that hypothesis, males exhibit similar responses to dead females in laboratory bioassays, but not to solvent‐washed dead females with their cuticular hydrocarbons removed. The mating response of males is restored when solvent extracts are reapplied to carcasses of solvent‐washed females, indicating that the contact pheromone is present in solvent extracts. Solvent extracts of the female cuticle contain six methylalkanes that are not present in extracts of males, three of which (7Me‐C₂₅, 7Me‐C₂₇ and 9Me‐C₂₇) constitute almost 40% of the total hydrocarbons. The bioactivity of these three compounds is tested by applying synthetic standards to solvent‐washed carcasses of females and presenting them to males. Standards are tested singly, pairwise and as the complete blend; freeze‐killed females serve as controls. Males attempt to couple with solvent‐washed female carcasses treated with 7Me‐C₂₇ alone and in combination with 9Me‐C₂₇ but only the complete blend elicits the same number of mounting and coupling attempts as does the control. These findings suggest that 7Me‐C₂₇ (7‐methylheptacosane) is the major component of the contact sex pheromone of N. a. acuminatus and that 7Me‐C₂₅ and 9Me‐C₂₇ act as synergists.     

Vertical distribution of codling moth adults in pheromone-treated and untreated plots

The vertical distribution of codling moth,Cydia pomonella (L.) within pheromone-treated and untreated apple and pear orchard canopies was determined using tethered virgin females, unbaited sticky traps, and blacklight observation of released moths. Mating of virgin females tethered at various heights in untreated orchard canopies increased with placement height from 1–4 m. Application of pheromone dispensers for mating disruption at 2 and 4 m above the ground greatly decreased mating. Greatest capture of males and females on unbaited sticky traps occurred at mid- and upper-canopy heights. Total capture of males and females in pheromone-treated plots was not statistically different than in untreated plots. The percentage of mated females captured on sticky traps did not vary with trap height or pheromone treatment. Released moths marked with flourescent powder and observed at dark with a blacklight indicated that moths are primarily distributed high in the canopy. However, males shifted to a position lower in the canopy when pheromone dispensers were placed 2.1 m above the ground. Results suggest that pheromone dispensers be placed in the upper canopy for optimal disruption of codling moth mating.     

Timing of mate-locating by males in relation to female activity in the carpenter beeXylocopa varipuncta (Hymenoptera: Apidae)

Males of the carpenter beeXylocopa varipuncta Patton wait for females to visit them as they hover at landmark territories along ridgelines on some spring afternoons. While hovering, males advertize their presence by releasing a pheromone that attracts passing females. If males have limited time to invest in territorial hovering and signaling, then they should engage in these activities more often at times when mate-searching females are most likely to visit landmark territories. The number of females flying near male territories varies greatly over the course of afternoons and from day to day. Measures of female activity and male territorial activity were highly correlated at one study site, both in terms of changes within afternoons and in terms of day-to-day fluctuations. This result supports the hypothesis that males ofX. varipuncta time their mateattracting behavior to maximize contacts with receptive females.     

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.