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.     

Field sampling of the tick Amblyomma variegatum (Acari: Ixodidae) on pastures in Guadeloupe; attraction of CO2 and/or tick pheromones and conditions of use

Field experiments were conducted in Guadeloupe to evaluate the attraction of different chemicals on a Guadeloupean strain of Amblyomma variegatum. Such tick sampling techniques may help to assess the size of the tick population on pastures before, during and after an attempted tick eradication campaign. CO2 was absolutely necessary to activate ticks, including the larvae. In addition to activation, our data suggested that CO2 itself is attractive for ticks. The reactivity of the ticks varied greatly with the period of the year, the adults being insensitive to CO2 alone or combined with pheromones for a period extending from December to June. For the whole period, the total captures were equal for the males and females, but the males were relatively more sensitive at the beginning of the season of activity (June–July), while the females dominated, but not significantly, for the rest of the period. There was also a gradient of reactivity depending on the distance from the trap; 28% of the ticks were captured at 0.5 m from the CO2 traps and 1.2% at a distance of 6 m. The ticks arrived rapidly at the trap. After 1 h of trapping, 55, 68 and 81% of the active nymphs, males and females, respectively, had reached the trap. Synthetic pheromones (methyl salicylate, o-nitrophenol and nonanoic acid in the proportions 1:2:8) or freshly detached males added to CO2, greatly increased the efficacy of the CO2 traps. Depending on the concentration of the pheromones, the attraction was four to 70 times higher than with CO2 alone. The effect depended on the sex of the ticks, males being attracted in a greater proportion by small amounts of pheromones, while the females were activated by higher doses. From a practical point of view, sampling should be conducted from June to December, with CO2 and high concentrations of pheromones, the traps being in operation for approximately 1 h at least, the area concerned by effluents being located downwind and covering an area of approximately 36 m2.     

Sex ratio and female sexual status of the coconut pest, Oryctes monoceros (Coleoptera: Dynastidae), differ in feeding galleries and pheromone-baited traps

Oryctes monoceros is a serious coconut pest, causing up to 40% damage in tropical Africa. Synthetic aggregation pheromone, ethyl 4-methyloctanoate, has been used to lure adults to traps. Traps with pheromone plus decaying palm material captured a high proportion of males. This raises the question whether individuals, which damage palms are receptive to the pheromone. We studied the sex ratio of the insects feeding on coconuts and those attracted to pheromone traps. Sixty two percent of adults from feeding galleries on living coconut palms were females. Pheromone with rotting palm material lured 43% females. To investigate the reasons for this difference, we compared the reproductive system of females lured to the odour traps or feeding in coconut galleries, or present in old rotting stems. Ninety six percent of the females trapped by pheromone had mated, and were sexually mature. In the galleries on living palms, 46% of females were immature, and 24% had not mated. In old rotting stems where eggs are laid and larvae develop, a mixture of 52% mated and 48% virgin females was found. Therefore, the pheromone together with the odour of rotting coconut stems signals a reproduction site to beetles, particularly mature females. In practice, the pheromone-baited traps will help in reducing the dissemination of gravid females, but will not affect directly the numbers of immature ones attacking palms. Our results show that when using pheromones for monitoring or controlling insects, the physiological status of the insects may have unexpected effects on the outcome.     

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.     

Influence of proportion of (4S)-cis-verbenol in pheromone bait on Ips typographus (Col., Scolytidae) catch in pheromone trap barrier and in single traps

Abstract:   The possibilities of increasing catching efficiency of male Ips typographus L in pheromone traps barriers and in single traps were tested. Pheromone dispensers with different percentages of (4S)- cis -verbenol (cV) in pheromone mixtures were used. The results show that the different male catching efficiencies of pheromone trap barriers and single traps were related to the different percentages of cV in the pheromone bait. The proportions of males were higher in pheromone trap barriers than in single traps. Thus increasing the catch of males in pheromone trap barriers is possible by using a combination of pheromone traps containing pheromones giving a higher release of cV with others containing pheromones giving a lower release of cV .     

Sex pheromone and visual trap interactions in mate location strategies and aggregation by host-alternating aphids in the field

Abstract. Field observations were made on the responses of males and gynoparae of three host-alternating aphid species, the blackberry-cereal aphid, Sitobion fragariae (Walker), the bird cherry-oat aphid, Rhopalosiphum padi (L.) and the damson-hop aphid, Phorodon humuli (Schrank) to species-specific sex pheromones released from transparent and coloured water traps.Pheromone traps caught significantly more males than did control traps without pheromone, whereas transparent, light green, yellow and orange traps caught most insects.Measurements of the distance over which sex pheromones function indicated that male P.humuli detect the pheromone 2–6 m from the source and can fly upwind to a source in wind speeds of 0.7 m s^-1.In all three species significantly more gynoparae were caught in pheromone traps than in control traps, suggesting that pheromone released by adult sexual females may assist late-flying gynoparae to locate a suitable host plant on which to deposit their progeny.The response is relatively stronger for males than gynoparae, but the pheromones appear to act as both sex and aggregation pheromones.     

Laboratory and field studies on the reproductive ecology of Parocneria orienta (Lepidoptera: Lymantriidae) in China

To lay a foundation for the monitoring, prevention and control of Parocneria orienta, a pest moth in China, we investigated the reproductive ecology of P. orienta, including the environmental factors affecting reproduction and the effects of pheromones in field traps. The results showed that the mating duration is shorter when the temperature is higher, with the optimal temperature range for P. orienta reproduction being 22–27°C. The sex ratio had an effect on the male mating capacity, which significantly increased when the sex ratio was ♀:♂ ≥ 3:1. The average number of matings was 2.44 for males, while female P. orienta mated only once in a lifetime. Males were more attracted to virgin females than to mated females, and the temperature and light period had an effect on the release of sex pheromones by females. Field trap tests using virgin females supported the results obtained in the laboratory, showing that the release of sex pheromones by P. orienta follows a distinct circadian rhythm.     

Evaluation of traps used to monitor southern pine beetle aerial populations and sex ratios

1 Various kinds of traps have been employed to monitor and forecast population trends of the southern pine beetle (Dendroctonus frontalis Zimmermann; Coleoptera: Scolytidae), but their accuracy in assessing pine‐beetle abundance and sex ratio in the field has not been evaluated directly. 2 In this study, we used fluorescent powder to mark pine beetles emerging from six isolated infestations. We then compared estimates of total abundances and proportions of males emerging from within each infestation to the estimates from three types of traps: passive sticky traps (2, 5, 10 and 20 m away from the source of beetles), multi‐funnel traps baited with pine beetle attractants (100 m away) and pine trees baited with attractants (also 100 m away). 3 We found that the proportion of males captured in traps was significantly affected by the type of trap used. 4 Within an infestation, equal proportions of males and females were marked (0.53 ± 0.02 males; mean ± SE), but the proportions captured in trap trees and passive traps were more female biased (0.42 ± 0.03 and 0.46 ± 0.01 males, respectively). On the other hand, funnel traps provided an estimate of the proportion of males that was nearly identical to the proportion from within infestations (0.51 ± 0.03). 5 Numbers of marked beetles captured in traps were uncorrelated with the numbers of marked beetles emerging from the focal infestations. This suggests that traps positioned around an infestation may not be effective at estimating relative abundances of beetles within the infestation.     

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.     

Sex ratios in laboratory and field populations of the old field mouse,Peromyscus polionotus

Males outnumbered females as juveniles but not as adults among mice captured by hand in their burrows. The higher production of male offspring together with their higher mortality rate resulted in a 1∶1 sex ratio for the adult mice. Despite the equal abundance of each sex, more males than females were caught in traps. Males must have a higher chance of encountering a trap and/or of entering a trap after finding it.     

Indirect female choice mediated by sex pheromones in the hermit crab Pagurus filholi

Males of the hermit crab Pagurus filholi perform precopulatory guarding behavior, and solitary males often show aggressive behavior to take away guarded females. Males behave coercively while guarding females, so direct mate choice by females seems difficult in such a situation. By performing several experiments we examined possible indirect female choice of hermit crab. Males were attached to a shell by their left cheliped to look like guarding pairs (fake guarding pairs). The shells were filled with cotton containing either seawater or pheromone water. The fake guarding pair with only seawater caused male–male combat in 60% of trials whereas with pheromone water combats occurred in 88% of trials. Mean duration of male–male combat was significantly longer in trials with drops of seawater containing pheromones than in those without pheromones. These results suggest guarding pairs themselves cause male–male combat by visual stimulation, that female sex pheromones have further significant function in the recognition of guarding pairs and intensification of male–male combat, and that females release sex pheromones while they are guarded. As a result of the combat, the larger male ended up guarding a female. This strongly suggests that females choose males indirectly by exploiting male–male competition induced by sex pheromones under male coercive behavior.     

Comparison of two synthetic food-odor lures for captures of feral Mexican fruit flies (Diptera: Tephritidae) in Mexico and implications regarding use of irradiated flies to assess lure efficacy

Feral Mexican fruit flies, Anastrepha ludens (Loew) (Diptera: Tephritidae), were trapped in a citrus orchard in Mexico by using two types of synthetic food-odor lures, the AFF lure (Anastrepha fruit fly lure, APTIV, Inc., Portland, OR) and the BioLure (two-component MFF lure, Suterra LLC, Inc., Bend, OR). In Multilure traps (Better World Manufacturing, Inc., Miami, FL) containing water, BioLures captured about the same numbers of flies as AFF lures. In Multilure traps containing antifreeze solution, BioLures captured 2 and 5 times more flies than AFF lures in two experiments. BioLures, and AFF lures did not differ in attractiveness when used on sticky traps (Intercept trap, APTIV, Inc.; and sticky cylinder trap). Multilure traps captured >4 times as many flies as sticky traps with the exception that captures of females did not differ between Multilure and sticky traps baited with AFF lures. The percentage of females captured in Multilure traps was greater when traps were baited with BioLures compared with AFF lures, but the reverse was true for sticky traps. Sticky cylinder traps captured a higher percentage of females than Multilure traps. The most effective trap/lure combination was the Multilure trap baited with BioLure and antifreeze. In comparison with tests of these two lures in Texas, results were similar for Multilure traps, but they differed for sticky cylinder traps in that AFF lures were consistently more attractive than BioLures in Texas, but not in Mexico.     

Potentials of Using the Pheromone Trap for Monitoring and Controlling the Bagworm,Metisa plana Wlk (Lepidoptera: Psychidae) on Young Oil Palm in a Smallholder Plantation

This study was carried out to investigate the potentials of using the pheromone trap for monitoring and controlling the bagworm, Metisa plana Wlk (Lepidoptera: Psychidae) on young oil palm in a smallholder plantation in southern Perak, Malaysia. Three types (Delta, Open-Delta, and Vane) of traps were evaluated with receptive virgin females as the pheromone sources. The Vane trap appeared to be most effective. Increase in pheromone sources resulted in more trap catches. The sticky Vane traps with receptive females showed potentials for mass trapping the bagworm, which resulted in reduced field population of bagworms.     

Influence of trap type, trap colour, and trapping location on the capture of the pine moth, Thaumetopoea pityocampa

Studies were conducted to evaluate the effect of type, location, and colour of traps baited with 1 mg of the sex pheromone (Z)‐13‐hexadecen‐11‐ynyl acetate in polyethylene vials on the capture of the pine processionary moth, Thaumetopoea pityocampa (Denis & Schiffermüller) (Lepidoptera: Thaumetopoeidae), males. The experiments were carried out during two flight seasons in 2002 and 2003 at a low elevation Mediterranean pine forest on the hill of Goritsa (Magnesia, Thessaly, Central Greece). The hill is covered by approximately 120 ha of pines, among which Pinus brutia Ten. (Pinaceae) is predominant with Pinus halepensis Mill. (Pinaceae) as second most common species. Among the commercially available trap types used, the Delta and Pherocon II captured significantly more males than the Funnel trap. Furthermore, pine density had a significant effect on trap type and trap colour catches. Delta traps caught significantly more adults than the other two trap types in the low density pine stand, while in the medium and high‐density pine stands no significant differences were noted between Delta and Pherocon II traps. In addition, trap colour performance varied according to pine density; white‐ and yellow‐coloured traps caught significantly more males than the other two trap colours in the high‐density stand. The first adults were captured in traps during May, and traps continued to capture adults in low numbers (< two individuals per trap) until mid‐June. A period of 3–4 weeks of no trap captures followed until mid‐July, when captures restarted, at low numbers. The peak of T. pityocampa flight was observed during late August–September.     

Efficacy of 1,4-diaminobutane (putrescine) in a food-based synthetic attractant for capture of Mediterranean and Mexican fruit flies (Diptera: Tephritidae)

Field trials were conducted in Guatemala to evaluate the importance of 1,4 diaminobutane (putrescine) in traps baited with ammonium acetate, trimethylamine, and putrescine. For the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), there were no differences in percentage of females captured in coffee and citrus or in percentage of males captured in citrus in traps with ammonium acetate and trimethylamine lures (females in coffee, 26.4 +/- 6.27%; females in citrus, 35.7 +/- 5.35%; males in citrus, 37.7 +/- 7.48%) versus ammonium acetate, trimethylamine, and putrescine lures (females in coffee, 36.6 +/- 9.64%; females in citrus, 41.1 +/- 5.18%; males in citrus, 37.1 +/- 6.09%). Percentage of males captured in coffee was reduced significantly when putrescine was not used with the ammonium acetate and trimethylamine (39.9 +/- 4.34 versus 31.6 +/- 5.29%). Lower percentages were captured in traps baited with ammonium acetate and putrescine, and the lowest percentages were captured in traps baited with putrescine and trimethylamine. When population level as indicated by capture in traps baited with ammonium acetate, trimethylamine, and putrescine was considered, a higher percentage of C. capitata males were captured in traps baited with all three components when one or more flies per trap per day were captured in coffee, and a higher percentage of females were captured when less than one fly per trap per day was captured in citrus. Percentage of the Mexican fruit fly, Anastrepha ludens (Loew), captured was significantly higher in traps baited with ammonium acetate and putrescine and significantly lower in traps baited putrescine and trimethylamine than in all other treatments. Results indicate that putrescine may be deleted when monitoring established populations of C. capitata but should be used in traps used to monitor A. ludens or to detect new infestations of C. capitata.     

A test for the production of sexual pheromones by Daphnia magna (Crustacea: Cladocera)

SUMMARY. (1) Swarming in the Cladocera has often been associated with periods of sexual reproduction and this has led to the suggestion that members of opposite sex are attracted to one another. The most plausible mechanism by which this could occur is through the production of pheromones. The present experiments aimed to determine if Daphnia magna Straus produce such chemicals.
(2) No evidence was found for the presence of sexual pheromones. The behaviour of both males and females was unaffected by the presence of sexually receptive animals of the opposite sex.
(3) It is suggested that the cited relationship between sexual reproduction and swarming may be due to the fact that sexual reproduction occurs during periods of high population density. It is during such periods that swarming behaviour would be most apparent.     

Male southern water skinks (Eulamprus heatwolei) use both visual and chemical cues to detect female sexual receptivity

A wide range of organisms use chemical and visual cues in mate attraction and courtship; however, chemical discrimination relevant to reproduction and the interplay between these two types of communication are poorly understood in reptiles. We experimentally tested the ability of male Eulamprus heatwolei, a scincoid lizard, to discriminate between sexually receptive and non-receptive females in two ways. First, we conducted 155 staged encounters between males and females over 29 days to determine the start and the duration of the female receptive period based on the date of copulations. These data suggest that the receptive period lasted for approximately 7 days in late October under controlled laboratory conditions. We also recorded 6,330 individual male and female behaviours during these trials to evaluate the frequency of female courtship and rejection behaviours and the intensity of male courtship behaviour. Female courtship increased sharply during the receptive period and then diminished. The disparity between female courtship behaviours and female rejection behaviours was greatest during the receptive period. Male courtship intensity increased sharply prior to the receptive period, peaked during the receptive period and thereafter declined rapidly. To determine if males were using visual cues, chemical cues or both from females, we conducted an experiment during and after the receptive period wherein male lizards were presented with a choice of two retreat sites treated either with the odour of large sexually receptive females, odour of small sexually non-receptive females or no odour (control). Males preferred the scent of females over the odourless control, and analysis using a special form of a generalized linear model, the Bradley–Terry model, showed a clear order of retreat site preferences, with large sexually receptive females favoured over small non-receptive females over the odourless control. We speculate that males use vision to find females and then use their chemosensory ability to chemically evaluate female sexual receptivity once the pair are in close proximity.     

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.     

Role of host volatiles in mate location by the Japanese pine sawyer, Monochamus alternatus hope (Coleoptera: Cerambycidae)

We evaluated the responses of male and female Monochamus alternatus Hope (Coleoptera: Cerambycidae) to various terpenes commonly associated with host trees. Electroantennogram (EAG) tests were conducted with 12 plant volatile compounds and ethanol. Antennae of both sexes were highly sensitive to (R)-(+)-alpha-pinene, (+)-3-carene, (-)-beta-pinene, and terpinolene. Both sexes of M. alternatus were attracted by traps baited with (+)-alpha-pinene, (-)-beta-pinene, (+)-3-carene, or terpinolene. Our results support the first of the three-stage hypothesis posed by Ginzel and Hanks that suggests that location of stressed trees by cerambycids involves three stages: (1) both sexes locate larval hosts by using plant volatiles as kairomones; (2) males produces sex pheromones to attract females after both sexes land on the larval hosts; (3) males and female recognize each other by contract pheromones in their epicuticular wax layer. Males and females showed differences in their EAG responses to several compounds, including (R)-(+)-alpha-pinene, (-)-beta-pinene, myrcene, (+)-3-carene, (R)-(+)-limonene, terpinolene, and trans-caryophyllene. In all cases, males exhibited greater sensitivity than females. In laboratory assays, male M. alternatus showed strong preference for 1% (+)-alpha-pinene and 1% (-)-beta-pinene over other compounds. In field assays, traps baited with (+)-alpha-pinene, (-)-beta-pinene, (+)-3-carene, or terpinolene caught more beetles than control traps. We found strong male bias in beetle catches in baited traps and those captured on the stem of stressed trees despite a strong female bias in emerging beetles in 2004. We hypothesize that male M. alternatus are more responsive than females to plant volatiles and that males have more capacity than females in finding mating locations.     

Life table assay of field-caught Mediterranean fruit flies, Ceratitis capitata, reveals age bias

Though traps are used widely to sample phytophagous insects for research or management purposes, and recently in aging research, possible bias stemming from differential response of individuals of various ages to traps has never been examined. In this paper, we tested the response of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) males and females of four ages (spanning from 1 to 40 days) to McPhail-type traps baited with a synthetic food attractant in field cages and found that the probability of trapping was significantly influenced by age. The type of food on which flies were maintained before testing (sugar or protein) also had a strong effect and interacted with age. In another experiment, we collected wild C. capitata adults of unknown age using 1–3 methods and then reared them in the laboratory until death. The survival schedules of these flies were subsequently used in a life table assay to infer their age at the time of capture. Results showed that on a single sampling date, males captured in traps baited with a food attractant were younger compared with males aspirated from fruiting host trees, or males captured in traps baited with a sex attractant. Likewise, females captured in food-baited traps were younger compared with aspirated females. In addition to providing the first evidence of age-dependent sampling bias for a phytophagous insect species, this paper also provides a novel approach to estimate the differences in the age composition of samples collected with different techniques. These findings are of utmost importance for several categories of insects, medically important groups notwithstanding.