Orientation to sex pheromone in the American cockroach: Analysis of chemo-orientation mechanisms

Male Periplaneta americana were photographed in a 2.4 m diameter arena containing a female sex pheromone source in the centre. Orientation pathways were digitized and analysed with regard to chemo-orientation mechanisms employed. Indirect components of chemo-orientation include arrestment near the pheromone source owing to an increase in turning rate and decrease in rate of locomotion, and zig-zag motor patterns that facilitate localization of the source. Most males were successful in locating the source if they moved to within 30 cm. Direct components of chemo-orientation include looping and relatively sharp correcting turns.No significant differences in orientation were observed between intact and unilaterally-antennectomized males, except that correcting turns close to the pheromone source were significantly less precise in males with one antenna. These results indicate that males with two antennae have an advantage over males with one antenna in being able to employ simultaneous information processing close to the pheromone source. Males with crossed antennae were unable to locate the pheromone source, suggesting that the fixed position of their antennae interfered with sensory information input.     

Orientation of male gypsy moths,Lymantria Dispar (L.), to pheromone sources: The role of olfactory and visual cues

The role of olfaction and vision in the close-ranging flying and walking orientation of male gypsy moths, Lymantria dispar(L.), to females was studied in the forest and in the laboratory. In the forest, feral males found an isolated pheromone source as readily as one supplemented with female visual cues; dead, acetonerinsed females deployed without pheromone received virtually no visitations. In flight tunnel choice experiments using cylinders as surrogate trees and pheromone in different spatial configurations, visual attributes of the female did not influence either the males' choice of landing site or the efficiency with which they located the female. Rather, the presence of pheromone on the cylinder was necessary to elicit orientation as well as landing and walking on the cylinder. When a female visual model was placed in various positions around a pheromone source, walking males oriented primarily to the chemical stimulus. There were, however, indications that males would alter their walking paths in response to female visual cues over short distances (<5 cm), but only if they continued to receive pheromone stimulation. When visual and chemical cues were abruptly uncoupled by altering the trajectory of the pheromone plume, most males responded to the loss of the odor cue rather than to visual cues from the female. Temporal pheromone stimulation patterns affected male walking orientation. When stimulated by pheromone, males oriented toward the source; loss of the odor cue prompted an arearestricted local search characterized by primarily vertical and oblique movements with frequent reversals in direction. Presumably these maneuvers enhance the likelihood of recontacting the plume or serendipitously encountering the female. The apparent lack of visual response to the female is discussed in light of morphological and behavioral evidence suggesting that gypsy moths were formerly nocturnal.     

Host odours enhance the responses of adult Rhyzopertha dominica to male-produced aggregation pheromone

The behavioural responses of adult male and female Rhyzopertha dominica (Coleoptera, Bostrichidae) to blends of host volatiles and male-produced aggregation pheromone were observed in a four-arm airflow olfactometer. The odour sources used were five pheromone-releasing males each on a single maize grain (lower maize-volatiles blend), five pheromone-releasing males on 500 g of maize (higher maize-volatiles blend) or the host volatiles emanating from 500g of maize (maize volatiles alone). Multiple-choice tests, in which volatiles from all three odour sources were presented in the exposure chamber at the same time, were used to study odour preferences of the males and females. Both sexes showed strongest attraction to the higher maize volatile blend but there were significant sex differences in response to the odour sources. Males spent significantly more time than females in the zone with only maize volatiles, and females spent significantly more time in the higher maize-volatiles zone. However, when odour sources were offered singly, females gave numerically greater responses than males to all sources although this difference was statistically significant for only the lower maize-volatiles blend. As males are more attracted than females to host odours alone it is suggested that they may be more highly adapted to seek out new hosts while females are more inclined to locate a food source by following the pheromone signals produced by males. However, both sexes responded most strongly to the odour source comprising aggregation pheromone with the higher proportion of maize volatiles.     

Mating behavior ofXylotrechus pyrrhoderus Bates (Coleoptera: Cerambycidae). VI mating system

Observations made in an outdoor cage showed that most pairings of the grape borerXylotrechus pyrrhoderus Bates were formed via inflight orientation of females towards pheromone-releasing males. The male sex pheromone induced orientation behavior in flying females, as well as walking approaches and prolonged lingering periods near the pheromone source in alighting females. When an approaching female failed to elicit any response in a male (e.g., when the male was copulating), she touched and sometimes mounted him. This behavior stimulated the males and often resulted in successful copulation. The male usually inseminated the second female, and the male's fitness increased when the second mating occurred more than 5 min after the start of the firt mating. These results suggest that male-like behavior in females (i.e., approaching and mounting behavior) has biological significance. The grape borer sometimes forms pairs via incidental encounters of the sexes. This is the same as the prevailing mating system of cerambycids. It is suggested that the male sex pheromonemediated mating system of the grape borer developed from the prevailing system of cerambycid groups.     

The influence of conspecific chemical cues on walking behavior of <Emphasis Type="Italic">Ixodes ricinus</Emphasis> males

The influence of female and male cues on the male searching behavior of the sheep tick, Ixodes ricinus (Acari: Ixodidae), was studied under constant laboratory conditions by means of a computerized video tracking system. Males were released into an open glass arena in which one half had been exposed for 1 h to 5 freely walking unfed females or five males. The obtained track data were analyzed to reveal if male walking pattern was random or affected by cues of conspecifics left on the arena surface. The results showed that males spent significantly more time and walked a significantly longer distance in the area with female cues compared to the control area. Moreover, the walking path of males was more tortuous on the cues half than the control half. In contrast, walking behavior of males was not affected by male cues in any observed parameter. These results provide the first evidence that unfed females leave sex-specific semiochemicals on a substrate during their walk and that these cues have an effect on male searching behavior. Since this effect was not observed when female cues were 24-h old, the semiochemicals seem to either evaporate or are subject to degradation. The biological significance of these findings for mate-searching in I. ricinus males is discussed.     

Sublethal exposure to methoxyfenozide-treated surfaces reduces the attractiveness and responsiveness in adult oriental fruit moth (Lepidoptera: Tortricidae)

The chemical communication (female attractiveness and male responsiveness) of adult oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide for 48 h were investigated in two laboratory wind tunnel assays. The recapture assay examined the ability of treated males to orient to a single cage of treated females, and the data gathered were mean percentage of males recaptured per treatment. The male sexual behavior assay examined some specific orientation behaviors (associated with sexual excitability) of treated males when they were given a choice of two competing pheromone sources (cages of treated females), and the data gathered were mean time males spent in upwind plume orientations and at source contact (female cage) per treatment. Data from the recapture assay suggests that exposure to methoxyfenozide impacts male responsiveness more than female attractiveness. In contrast, data from the sexual behavior assay strongly revealed that exposure to methoxyfenozide-treated surfaces does negatively impact both the ability of calling females to attract males and of aroused males to display sustained upwind flight behavior and time spent at the female cages.     

Pre-exposure modulates attraction to sex pheromone in a moth

In behavioural experiments we investigated the influence of previous short exposure to sex pheromone on subsequent response of male Spodoptera littoralis moths to sex pheromone. We found that pre-exposed males showed increased sensitivity to female sex pheromone after a single exposure to a pheromone plume compared to that found in na?ve males. The increased responsiveness lasted for at least 27 h after the exposure, showing that it was not just a short-term sensitization of the males. Exposure to the odour source without upwind movement towards the source was enough to increase the responsiveness. Physical activation without exposure to odour did not affect responsiveness. The increase in responsiveness after exposure was higher when the males were pre-exposed to natural female pheromone gland extract than when they were exposed to a higher dose of the main component, even though both odour sources elicited similar upwind attraction in na?ve males. Thus, the quality of the pheromone mixture to which males were exposed influenced the subsequent response.     

The design of an olfactometer and a method for quantitative stud on the effect of odours on insect behaviour

Vertical air-flow olfactometer suitable for study of the influence of odours on walking insect behaviour was described. The results of preliminary experiments proved that the olfactometer enables long-lasting "quasiethological" observations. Employed method of observation gave quantitative information about the influence of odours on ratios of basic predeterminate activities, insect distribution pattern and their tendency to choose zones with an odour. The Colorado beetle (Leptinotarsa decemilineata Say) males preferred zones with the female odour spending there more time. During emission of the pheromone males were more active. In zones with the pheromone males displayed the tendency to cluster, spent more time taping intensely and more frequently attempted to mate.     

Behavioural responses of female Neogobius melanostomus to odours of conspecifics

The behavioural responses of reproductive and non‐reproductive female round gobies Neogobius melanostomus to water conditioned by reproductive and non‐reproductive males and females were tested. The behavioural responses of reproductive female round gobies exposed to odour of reproductive males included increased time spent near the source of the odour, elevated swimming velocities and directed movement to and around the odour source when compared with their responses to control water. These results suggested that pheromones released from reproductive males may induce spawning behaviour in reproductive females. Non‐reproductive females exposed to reproductive female odour spent significantly more time near the odour source of reproductive females compared with control water. Non‐reproductive females also showed directed movement towards and around the odour source when exposed to reproductive female odour. These results suggested that round gobies use inter‐sexual and intra‐sexual pheromones and that both sex and reproductive status are important in the detection and release of these pheromones.     

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.     

Male housefly (Musca domestica L.) genital system as a source of mating pheromone

Male volatile mating pheromone is released by male houseflies placed in close proximity to females or in contact with female hydrocarbon extract. The pheromone induces the aggregation of virgin females in the vicinity of the male. Preparations of macerated testicular and ejaculatory duct tissue exert a similar effect, and these organs are, apparently, the source of the pheromone. Such preparations are not attractive to males or mated females. The pheromone also appears to induce female receptivity, since females that are exposed to emanations from male system preparations show a quicker rate of pairing with males. The pheromone effect results from the testes and ejaculatory ducts acting together, as preparations of each of these alone are inactive. Pheromone activity is age dependent and the greatest female reaction is observed when tissues of 6–10-day old males are used.     

(11Z)-hexadec-11-enal enhances the attractiveness of Diatraea saccharalis main pheromone component in wind tunnel experiments

Abstract:  GC-EAD and GC-MS analysis of pheromone gland extracts of sugarcane borer, Diatraea saccharalis , revealed two antennally active compounds, (9 Z ,11 E )-hexadeca-9,1-dienal and (11 Z )-hexadec-11-enal, in approximately 10 : 1 ratio. Various doses of identified compounds were investigated in wind tunnel experiments individually and in a 10 : 1 ratio. At all tested doses (9 Z ,11 E )-hexadeca-9,1-dienal alone elicited upwind orientation and source location only in a minority of tested males. An admixture of (11 Z )-hex-11-enal enhanced the attractiveness of (9 Z ,11 E )-hexadeca-9,11-dienal significantly. This two-component blend (100 pg) was as attractive as natural pheromone extracted from three female pheromone glands. The data suggest that (11 Z )-hexadec-11-enal is a part of the D. saccharalis sex pheromone.     

Flight tunnel response of codling moth Cydia pomonella to blends of codlemone,codlemone antagonists and pear ester

Upwind orientation flights of codling moth males Cydia pomonella L. to a single source of sex pheromone (E,E)‐8,10‐dodecadienol (codlemone) are significantly reduced when blending it with pheromone antagonists, either with codlemone acetate, (E,E)‐8,10‐dodecadienyl acetate, or with the codlemone isomer (E,Z)‐8,10‐dodecadienol. However, once activated by a pheromone stimulus, males no longer distinguish between a pheromone source and these antagonistic blend sources. This shows that the pheromone stimulus required for the initiation of an upwind flight response differs from the stimulus for maintaining upwind flight and landing at the source. In contrast to pheromone antagonists, males discriminate between pheromone alone and a blend source of pheromone and the plant volatile pear ester, ethyl (2E,4Z)‐2,4‐decadienoate. This indicates a difference in the detection and neural integration of pheromone and plant volatile stimuli.     

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.     

Orientation of flying male Anobium punctatum (Coleoptera: Anobiidae) to sex pheromone: separating effects of visual stimuli and physical barriers to wind

Abstract. Flying male woodworm, Anobium punctatum , are able to locate a source of female pheromone offered as a point source but land more quickly if the same odour source is presented on a model 'tree' (cylinder). We tested the response to a two-dimensional black 'tree' marked as a silhouette on the upwind screen of the wind tunnel, with or without a hidden upwind barrier to the wind. The beetles responded equally to pheromone presented on a visual silhouette with wind barrier and to the hidden upwind wind-barrier alone, suggesting that the wind-barrier itself has a significant effect on insect orientation and landing: visual stimuli do not add to the landing response if the barrier is present. However, without the barrier upwind, landing was faster when the visual stimulus was present than without. This is the third forest-living species to be shown to respond in this way, which suggests this phenomenon may be more widespread. The possibility that this phenomenon is present in other, non-forest, phytophagous insects, their predators and parasitoids is discussed.     

The significance of blends of two sex pheromone components on the behavior of maleSpodoptera litura F. (Lepidoptera: Noctuidae)

Behavioral responses of maleSpodoptera litura to the female sex pheromone components, (Z, E)-9, 11-tetradecadienyl acetate (compound A) and (Z, E)-9, 12-tetradecadienyl acetate (compound B), and mixtures of compounds A and B were analyzed in the laboratory. Male orientation flight in a wind tunnel was induced by a lure dispenser onto which 1.1×10⁻³ ng of a mixture (A∶B=10∶1) was absorbed, while 1 ng of compound A was required to induced the same level of behavior. The blend ratio was important for trap catch and orientation flight of males and a 10∶1 mixture of compounds A and B was most effective. A mixture (10∶1) was more effective than compound A alone in induction of movement, walking, and flying in resting males in a glass tube. These results indicated that 2 sex pheromone components act as a set from the initial to final steps of male attraction to female.     

黄斑卷蛾雄蛾对性信息素的行为反应

分别在风洞中和田间观察了黄斑卷蛾Acleris fimbriana Thunberg et Becklin雄蛾对合成性信息素三种成分（E11,13-14∶Ald, E11,13-14∶Ac和E11-14∶Ac）及其不同组合的行为反应。在风洞中,主要活性成分E11,13-14∶Ald能引起雄蛾完成从兴奋到搜索释放源的行为反应,但雄蛾对单个组分E11,13-14∶Ac 或 E11-14∶Ac不呈现任何行为反应。当释放源为双组分 E11,13-14∶Ald＋E11,13-14∶Ac （6∶4）或三组分E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac（6∶4∶1）时,可以明显增加雄蛾定向飞行和到达释放源的数量。三组分 E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac的比例为6∶4∶1时,500 μg剂量效果最好。田间试验结果表明,E11,13-14∶Ald单独使用表现出良好的诱蛾活性,其诱蛾量为活雌蛾的1.9倍,而E11,13-14∶Ac和E11-14∶Ac则不具有诱蛾活性。E11,13-14∶Ac对E11,13-14∶Ald有明显的增效作用,三组分E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac（6∶4∶1）诱芯的诱蛾效果最好。     

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.     

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.     

Sex pheromone components of female Cornutiplusia circumflexa

Capillary gas chromatography indicated the presence of (Z)-7-dodecenyl alcohol and (Z)-7-dodecenyl acetate in the abdominal tip extracts of female Cornutiplusia circumflexa (L.) (Lepidoptera: Noctuidae: Plusiinae) moths. Gas chromatography combined with mass spectrometry and dimethyl disulfide derivatization confirmed the structure of these two principal pheromone components. In a flight-tunnel bioassay, a 5:1 blend of alcohol and acetate elicited the complete courtship sequence by males. The response was comparable to that evoked by a live virgin female, but males spent significantly longer time at calling females than at the synthetic source. The 5:1 blend was also attractive to male C. circumflexa in the field, as indicated by catches in traps baited with this mixture. (Z)-7-dodecenyl alcohol alone was slightly attractive whereas (Z)-7-dodecenyl acetate alone was completely inactive. C. circumflexa is the first reported Plusiinae species which utilizes (Z)-7-dodecenyl alcohol as the major pheromone component.