Re-examining the relationship between sexual maturation and age of response to methyl eugenol in males of the oriental fruit fly

Males of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), are strongly attracted to, and feed voraciously on, methyl eugenol (ME) and use metabolites of this chemical to synthesize their sex pheromone. Previously, Wong et al. (1989 ) proposed that B .  dorsalis males were attracted to ME even before attaining sexual maturity. However, their interpretation is possibly confounded by the fact that, in monitoring age-related mating readiness, males were presented with equal-aged females. As a result, if females mature more slowly than males, the age of male sexual maturation may have been overestimated, which may have accounted for the discrepancy observed between male age of ME responsiveness and mating activity. Here, we re-examined the relationship between male age and mating readiness by comparing male mating activity when presented with same-aged females vs. sexually mature females. In addition, we measured the age-dependent response of B .  dorsalis males to ME by recording (i) capture in ME-baited traps, and (ii) feeding duration on ME-containing paper discs. Our data support the conclusion of Wong et al. (1989 ) that B .  dorsalis males show attraction to, and feed on, ME before attaining sexual maturity, but suggest that a marked difference in ME response and mating activity exists over a shorter age interval than indicated by Wong et al. (1989 ). Early attraction to, but not ingestion of, ME was related to accelerated sexual maturation. Unexpectedly, ingestion of ME by sexually immature males did not boost their mating success in trials conducted 10 days after feeding on the lure.     

Methoprene-induced matings of young Queensland fruit fly males are effective at inducing sexual inhibition in females

Pre-release dietary treatment with methoprene, a juvenile hormone analogue, decreases the age at which male Queensland fruit flies mature and hence may decrease the post-release delay until released sterile flies participate in sterile insect technique (SIT) programmes. However, if matings of young methoprene-treated males are not effective at inducing sexual inhibition in their mates, then this treatment may not enhance SIT. The present study investigates efficacy of matings of methoprene-treated males at inducing sexual inhibition in their mates. Methoprene incorporated into a diet of sugar and yeast hydrolysate (w/w 3:1) for 48 hr after emergence resulted in significantly increased male mating propensity when flies were <10 days of age, but not when older, and longer copulations. Copula latency did not vary with methoprene treatment but did decrease with age. The matings of young methoprene-treated males were effective at inducing sexual inhibition in their mates, matching the efficacy of untreated mature males. Regardless of treatment, females had reduced tendency to remate if their first mate was 15 days of age than if their first mate was younger (6, 8 days) or older (20, 25, 30 days). Females mated by methoprene-treated males that did remate tended to remate later in the day than females mated by untreated males. Also, second copula durations of females first mated by a 6- to 10-day-old male were shorter if the male was methoprene treated. These patterns in remating females may indicate greater efficacy of the initial mating of methoprene-treated males. Overall, we find that the additional matings of young methoprene-treated male Queensland fruit flies are effective at inducing sexual inhibition in their mates. This finding supports the incorporation of methoprene into pre-release diet for SIT.     

Sexual selection in a tropical fruit fly: role of a plant derived chemical in mate choice

The specific mechanisms by which selective pressures affect individuals are often difficult to resolve. In tephritid fruit flies, males respond strongly and positively to certain plant derived chemicals. Sexual selection by female choice has been hypothesized as the mechanism driving this behaviour in certain species, as females preferentially mate with males that have fed on these chemicals. This hypothesis is, to date, based on studies of only very few species and its generality is largely untested. We tested the hypothesis on different spatial scales (small cage and seminatural field‐cage) using the monophagous fruit fly, Bactrocera cacuminata. This species is known to respond to methyl eugenol (ME), a chemical found in many plant species and one upon which previous studies have focused. Contrary to expectation, no obvious female choice was apparent in selecting ME‐fed males over unfed males as measured by the number of matings achieved over time, copulation duration, or time of copulation initiation. However, the number of matings achieved by ME‐fed males was significantly greater than unfed males 16 and 32 days after exposure to ME in small cages (but not in a field‐cage). This delayed advantage suggests that ME may not influence the pheromone system of B. cacuminata but may have other consequences, acting on some other fitness consequence (e.g., enhancement of physiology or survival) of male exposure to these chemicals. We discuss the ecological and evolutionary implications of our findings to explore alternate hypotheses to explain the patterns of response of dacine fruit flies to specific plant‐derived chemicals.     

Post-teneral protein feeding enhances sexual performance of Queensland fruit flies

Abstract.  Adult diet is an important determinant of sexual activity in many tephritid fruit flies. Whether availability of protein (hydrolysed yeast) in addition to sucrose influences sexual activity or longevity of male and female Queensland fruit flies ( Bactrocera tryoni Froggatt, 'Q-flies'), and whether irradiation of flies as pupae modifies their dietary needs, is investigated. Previous studies on groups of flies suggest that protein is required for sexual maturation of females but not males. By contrast, this study of individual flies demonstrates that protein in the adult diet provides a massive boost to sexual activity of both males and females. Mating probability increases with age from 4-14 days as the flies began to mature. However, mating probability reaches much higher levels when the flies are provided with protein. Although males and females mate at similar rates when provided with protein, females suffer a greater reduction in mating probability than males when deprived of protein. In addition to increased mating probability, access to dietary protein is also associated with reduced latency from onset of dusk until copulation. Furthermore, young male flies with access to dietary protein have longer copula duration than males fed only sucrose. Irradiation of flies as pupae has no apparent effect on mating probability, the latency to copulate or copula duration. However, when deprived of protein, sterile flies (especially males) suffer a greater reduction in longevity compared with fertile flies. Overall, access to dietary protein increases longevity for both males and females, although females live longer than males on both diets. These findings suggest that prerelease provision of dietary protein has the potential to greatly enhance the efficacy of Q-flies used in the sterile insect technique.     

Rapid cold hardening in the olive fruit fly Bactrocera oleae under laboratory and field conditions

A rapid cold hardening response was studied in females and males of the olive fruit fly Bactrocera (Dacus) oleae. When laboratory-reared females and males were transferred and maintained from the rearing temperature of 24 °C for 2 h to –6.5 °C approximately 5% survived. However, conditioning of both females and males for 2 h at various temperatures from 0 to 10 °C before their exposure for 2 h to –6.5 °C increased survival to 80 to 92%. A similar rapid cold hardening response in both females and males was also induced through gradual cooling of the flies at a rate of approximately 0.4 °C per min. The rapid increase in cold tolerance after prior conditioning of the flies to low temperatures, was rapidly lost when they returned to a higher temperature of 24 °C. In the field, in late February and early March, females and males were capable of a rapid cold hardening response. After exposure to the critical temperature they suffered a high mortality when tested in the afternoon and low mortality early in the morning on consecutive days, probably because of differences in the prevailing field temperatures a few hours before testing. This plasticity of cold tolerance gained through rapid cold hardening may allow the flies to survive during periods of the year with great fluctuation in circadian temperatures.     

Factors affecting the efficacy of trapping system to the peach fruit fly (PFF) males,Bactrocera zonata (Saunders) (Diptera: Tephritidae)

This study was conducted in Arab-Elmadabegh region located at the Northern West part of Assiut city at the border with the Western Desert. Four types of traps; Bottle trap, Glass McPhail trap, Plastic McPhail trap, and Abdel-Kawi trap baited with different doses of methyl eugenol (ME) were used. Obtained results indicated that Abdel-Kawi trap charged with 0.5?ml ME, it was the most effective trapping system. ME seemed to be with highly attracting effect, but most of the attracted males were found on the outside surface of the trap and on the branches surround the trap. Under these conditions, the females/males ration became 1:171. Thus, the believing tactic that fruit flies populations will decline due to the lack of males in the population available to females for mating seemed to be an erroneous believing. Results proved that PFF males had the highest activity at the dawn period between 5 and 7am. We strongly recommend using the trapping system consists of Abdel-Kawi trap charged with 0.5?ml ME only at dawn period (The first appearance of light in the morning followed by sunrise).     

Predation potential of the earwig Euborellia annulipes on fruit fly larvae and trophic interactions with the parasitoid Diachasmimorpha longicaudata

The earwig Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae), a generalist predator, has been observed in fruits infested with fruit fly larvae, which are frequently parasitized by parasitoid wasps. Neither the capacity of earwigs to predate on fruit flies nor intraguild interactions between earwigs and fruit fly parasitoids have been investigated. Here, we studied in laboratory conditions the predation on the fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) by the earwig E. annulipes, and whether parasitism of fruit fly larvae by the parasitoid wasp Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) influences predation by the earwig. We evaluated the predation capacity, functional response and prey preference of E. annulipes for parasitized and non-parasitized fruit fly larvae in choice and no-choice tests. We found that earwigs prey on second- and third-instar larvae and pupae of C. capitata and consumed larger numbers of second-instar larvae, followed by third-instar larvae and pupae. Females prey on larger numbers of fruit flies than did males, regardless of the prey developmental stage, but both sexes exhibited a type II functional response. Interestingly, males killed but did not consume fruit fly larvae more than did females. In no-choice tests, earwig females consumed equal numbers of parasitized and non-parasitized fruit fly larvae. However, in choice tests, the females avoided feeding on parasitized larvae. Subsequent tests with hexane-washed parasitized and non-parasitized larvae showed that putative chemical markings left on fruit flies by parasitoids did not drive the earwig preference towards non-parasitized larvae. These findings suggest that E. annulipes is a potential biological control agent for C. capitata, and that, because the earwig avoids consuming larvae parasitized by D. longicaudata, a combination of the two natural enemies could have an additive effect on pest mortality.     

Attraction and feeding responses of Mediterranean fruit fly and a natural enemy to protein baits laced with two novel toxins,phloxine B and spinosada

Studies were conducted to determine attraction and feeding propensity of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), to different protein bait mixtures with and without the insecticides malathion, spinosad, and phloxine B. Protein baits were more attractive to females than to males. Protein-starved females responded more than protein-fed females. The type of protein (USB^® yeast hydrolysate enzymatic, Mazoferm^®E802, Nu-Lure^®Insect Bait, or Provesta^® 621 autolyzed yeast extract) in the bait had a major influence on C. capitata attraction, which was strongest to fresh Provesta. Aged baits (four day-old) were not as attractive as fresh baits. In feeding propensity studies, highest response was observed for USB protein. On the basis of attraction and feeding responses Provesta (attraction and feeding) and USB (feeding) outperformed the standard Nu-Lure. Protein-starved flies were much more likely to feed on protein compared to protein-fed flies. For protein-starved flies, a mixture of Provesta and malathion repelled fruit flies, compared to a mixture of Provesta and spinosad or phloxine B. This was not the case with protein–fed flies. The wasp Fopius arisanus (Sonan), one of C. capitata's primary natural enemies in Hawaii, would not consume protein baits. Our studies suggest that spinosad or phloxine B, with low contact toxicity, mixed with protein baits offers a more environmentally friendly choice for control of C. capitata and conservation of F. arisanus, whereby the nontarget effects of broad spectrum contact poisons such as malathion can be avoided. Presumably, due to greater selectivity with spinosad and phloxine B bait treatments, the host would be killed, but not the natural enemy.     

Methyl eugenol effects on Bactrocera dorsalis male total body protein,reproductive organs and ejaculate

Methyl eugenol (ME) and inclusion of protein into the adult diet increase the mating competitiveness of the Oriental fruit fly, Bactrocera dorsalis (Hendel). Exposing males to ME or protein is a promising post‐teneral treatment for males being released in the sterile insect technique (SIT). However, the effect of this post‐teneral treatment on male reproductive organs or the male ejaculate is unknown. During mating, males transfer sperm and accessory gland products (AGPs) to females and these compounds are reported to modulate female sexual inhibition. We studied the impact of male exposure to ME and a yeast hydrolysate (YH) diet on the protein reserves of males, male reproductive organ size, and the male ejaculate through sperm and AGPs. We show that males exposed to ME regardless of access to YH accumulated a greater amount of whole body protein. Males fed on YH also had increased total body protein and had bigger reproductive organs than YH‐deprived males, but no apparent effect of ME exposure was observed on reproductive organ size. Females stored less sperm when mated with males fed on YH and ME compared to males not fed on ME. YH and ME had no effect on male AGPs. Females injected with AGPs of males fed on YH and exposed to ME were just as likely to mate as females injected with AGPs of non‐treated males. However, females injected with AGPs of males exposed to ME mated faster than females injected with AGPs of non‐exposed males. We conclude that while exposure to ME increases male copulatory success and protein reserves in the male body, there seem to be some potential trade‐offs such as lower sperm stored by females. We discuss our results in terms of pre‐release protocols that may be used for B. dorsalis in SIT application.     

Behavioural switch of female Mediterranean fruit fly, Ceratitis capitata: mating and oviposition activity in outdoor field cages in Hawaii

1 Laboratory-reared normal, and wild female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), were assayed in outdoor field cages to assess the impact of a mating-induced behavioural switch on mating and subsequent oviposition activity. 2 Virgin females preferred interactions with males leading to mating over attraction to, and oviposition in, artificial yellow spheres containing guava odour or green apples hung in a guava tree. Laboratory-reared females previously mated with either laboratory-reared normal males or laboratory-reared irradiated (sterile) males showed little interest in remating with males and instead, were much more likely to be found arrested on artificial and real fruit and ovipositing. Oviposition on artificial fruit was five times greater by females that had mated with either normal or irradiated males than by virgin females. Wild females showed similar qualitative changes in the mating-induced behavioural switch; however, oviposition activity was significantly less than for laboratory-reared females. 3 These results confirm that mating has a profound effect on the behaviour of female Mediterranean fruit flies and that irradiated males are functionally equal with normal males (lab-reared or wild) in their ability to alter female behaviour. These results are discussed in the context of the sterile insect technique for control of Mediterranean fruit flies in the field.     

Attraction of Mexican Fruit Flies (Diptera: Tephritidae) to Grapefruit: Enhancement by Mechanical Wounding of and Experience with Grapefruit

Wild strain, mated, female Mexican fruit flies, Anastrepha ludens (Loew), with no prior experience with fruit (naive), were not attracted to grapefruit, a preferred cultivated host, in wind tunnel experiments. Naive, mated laboratory strain females were attracted. Prior experience with grapefruit increased attraction of both laboratory and wild strains. More females were attracted to fruit with peel damage than to undamaged fruit, indicating that fruit odor mediated attraction. More naive than experienced females attempted to oviposit on the sides of the wind tunnel. Experienced laboratory males, but not wild males or naive males, were attracted to grapefruit. Attraction and oviposition behavior of laboratory flies was greater than that of wild flies.     

Feeding substrates and behaviors of Western cherry fruit fly (Diptera: Tephritidae)

A study was conducted to determine the abundance of potential foods and the feeding substrates and behaviors of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in 2005, 2006, and 2007 in central Washington state. Aphid colonies with honeydew, a presumed food source for flies, were not seen on randomly selected branches of sweet cherry trees, Prunus avium L., but leaves with cherry juice, fruit that were damaged, and leaves with bird feces were commonly seen, especially later in the season. Grazing, a behavior in which the mouthparts rapidly move up and down and touch plant surfaces without discrete substances visible to the human eye, was seen more frequently in flies on leaves than on fruit. Grazing occurred more frequently than feeding on extrafloral nectaries (EFNs) on leaf petioles, cherry juice on leaves, and bird feces on leaves. The percentages of females and males that grazed on leaves were not different in 2 of 3 yr, but the percentage of females that grazed was higher in a third year. Percentages of female and male flies that fed on EFNs, cherry juice, and bird feces did not differ. More flies grazed the tops than bottoms of leaves. Flies also grazed on leaves of apple, pear, and grape. The results support the hypotheses that R. indifferens feeds mostly on leaves rather than fruit and that leaf surfaces may be the main feeding substrates for R. indifferens throughout the season.     

Social interactions regulate resource utilization in a Tephritidae fruit fly

Previous studies have suggested that social interactions (e.g., the actions and reactions elicited by the interaction of co-specific individuals) induce individual fruit flies (Tephritidae) to ingest more food, especially protein-rich food. Changes in feeding behavior related to social interactions have been associated with reproduction (e.g., when different sexes are present), reproductive facilitation (e.g., when two females interact) and stress and aggression (e.g., flies of the same sex, or crowdedness). The present study investigated the effect of social interaction on the feeding, longevity and resource management of the Ethiopian fruit fly, Dacus ciliatus. Single flies and pairs of flies (of the same or different sexes) were confined to a small arena (the PUB system), in which we measured the amount of liquid food ingested daily by each fly. In addition, we sampled flies of different ages, extracted and quantified their lipid and protein contents, and related individual metabolic contents to the ingestion of a fructose and protein hydrolysate solution. Results showed that individual ingestion was significantly higher in flies maintained in pairs than in flies kept as solitary individuals. The highest intake rates were observed for the female–female pairs. In general, females ingested significantly greater volumes than males. Lipid contents tended to decrease progressively with age in flies kept as solitary individuals, especially in female flies, while lipid levels decreased and then increased in flies maintained in pairs. Protein trends were similar, although less pronounced than the patterns observed for the lipids. The flies kept as solitary individuals lived significantly longer than those kept in pairs. A resource-management analysis points to a decreased metabolic rate in flies kept as solitary individuals, as compared to paired flies. Results are discussed in view of theories of resource management and survival strategies.     

Adult diet and male-female contact effects on female reproductive potential in Mexican fruit fly (Anastrepha ludens Loew) (Diptera tephritidae)

Wild strains of fruit flies (Diptera: Tephritidae) placed into laboratory rearing conditions are subjected to selection pressures caused by the diet, cages, density of flies, and other factors. Selection that changes mating behavior of the strain may result in less effective males released in sterile insect programs. Tests were performed to examine the effects of protein in diet and adult interactions on egg production and mating during sexual maturation of the Mexican fruit fly (Anastrepha ludens Loew) in laboratory cages. Flies were offspring of wild flies collected from Chiapas or Nuevo Leon, Mexico, and reared on Valencia oranges. Experiments demonstrated effects of yeast hydrolysate protein in adult diet and pairing with males on production of mature and immature eggs, numbers of females producing eggs, and mating with females aged 15 d. Addition of protein to 4% fructose in the adult diet approximately tripled mature egg production in females maintained for the total maturation period with an equal number of males. Females that matured without males produced approximately 33% more-mature eggs when fed protein than those fed no protein. Total egg production of females matured without males and fed sugar only or sugar with protein was more than twice that of females matured with males. Tests to examine the effects of male and female diet separately on female egg production showed slightly higher egg production in females fed protein, or females paired with males fed protein, but these differences were not significant. The most definitive effects were that combining wild strain females and males in cages during maturation reduced egg production. This effect was greatest when flies were not fed protein.     

Effect of bacteria on nutritional status and reproductive success of the Mediterranean fruit fly Ceratitis capitata

Abstract.  Mediterranean fruit flies ( Ceratitis capitata Wiedemann, Diptera: Tephritidae) harbor a community of diazotrophic bacteria in their digestive system. The present study aims to test the hypothesis that bacteria contribute to fly fitness by enhancing copulatory success and egg production in males and females, respectively. After eclosion, flies were fed a full diet containing peptides, sugar and minerals, or a sugar diet, lacking peptides. Subgroups from each diet were fed a mixture of the antibiotics ciprofloxacin and piperacillin. The presence of bacteria, food consumption, weight gain, lipid and protein levels, oviposition in females and copulatory success of males were quantified in the four groups. The antibiotic treatment effectively cleared the gut of bacteria. The relative amounts of food consumed (with or without antibiotics) are similar in all groups. The antibiotics do not inhibit feeding, and their ingestion does not affect dry weight or the amount of protein stored, yet females feeding on the full diet without antibiotics have increased lipid levels. Females fed the full diet produce significantly more eggs than females on the sugar diet, but the presence of bacteria does not affect numbers of eggs produced. However, in the absence of bacteria, the oviposition rate of nutritionally stressed females is significantly accelerated. The presence of bacteria in sugar fed males does not provide them with a mating advantage. Conversely, in males fed a full diet, the presence of bacteria is associated significantly with a shorter latency to mate. It is concluded that, because the bacterial community is present at all stages of the fly's life cycle, at least some species are effectively transmitted from parents to offspring, and removal of bacteria affects measurable physiological and behavioural parameters related to fitness, the association between bacteria and the medfly is mutualistic.     

Attraction of feral Bactrocera dorsalis males (Diptera: Tephritidae) to natural versus commercial sources of methyl eugenol

Males of Bactrocera dorsalis (Hendel) are strongly attracted to methyl eugenol (ME), which occurs in over 450 plant species. Given this powerful attraction, ME is commonly used in surveillance and eradication programs against this invasive agricultural pest. Preliminary observations revealed that B. dorsalis males visited ME-bearing flowers of the fruit fly orchid (FFO) Bulbophyllum cheiri subsp. cheiri even when these occurred near traps baited with far greater quantities of ME. Based on this evidence, we undertook field experiments to assess the attraction of feral B. dorsalis males to FFO flowers relative to commercial sources of ME. At the edge of a secondary forest, an FFO flower was placed midway between two ME sources located 20 m apart, and attracted flies were collected over an entire day. When the ME sources were unenclosed (not in traps), the relative attractiveness of FFO flowers to B. dorsalis males varied with the amount of ME placed nearby. The FFO flower (i) attracted a similar proportion of males when 1 g ME was placed at the flanking sites but (ii) captured significantly smaller proportions when the nearby sites had 6 or 10 g commercial ME sources. Similar tests with the commercial sources enclosed in traps showed that (i) 6 g ME sources in Steiner traps attracted significantly more B. dorsalis males than FFO flowers but (ii) 10 g sources in Clear traps (1 L buckets with 4 entrance holes) did not outperform the FFO flowers, presumably owing to limited dispersion of volatiles from the trap. Implications of these results for surveillance programs are discussed.     

Condition-Dependent Mating Success in Male Fruit Flies: Ingestion of a Pheromone Precursor Compensates for a Low-Quality Diet

Previous studies revealed that males of the oriental fruit fly, Bactrocera dorsalis, require protein in the adult diet to obtain matings and that ingestion of methyl eugenol, which acts as a pheromone precursor, increases male attractiveness and mating competitiveness. The goal of this study was to investigate the interaction between diet quality and methyl eugenol consumption in affecting the mating frequency of B. dorsalis males. In one set of experiments, mature males were deprived of protein for 1, 3, or 7 days and were either given or denied access to methyl eugenol (ME). These males competed against control males (continuously protein-fed, no feeding on ME) for copulations in field cages. Without ME, males held without protein for 3 or 7 days obtained significantly fewer matings than control males. With ME, however, males held for even 7 days without protein achieved higher mating success than control males. In a second set of experiments, mature males were held without protein for 7 days and then given a protein-rich diet for 1, 3, or 7 days before testing and were either given or denied access to ME. Without ME, males were competitively inferior to control males when tested 1 or 3 days after resumption of protein feeding and equivalent to control males only after 7 days of protein feeding. With ME, however, males obtained significantly more matings than control males when tested 3 or 7 days after resumed protein feeding and had similar mating success as control males after 1 day of access to the protein-rich diet. Results show that mating success in this species is condition-dependent, with both nutritional state and ME consumption influencing male mating success. Under the test conditions, feeding on ME counteracted a low quality diet and enhanced male mating success.     

Functional significance of phytochemical lures to dacine fruit flies (Diptera: Tephritidae): an ecological and evolutionary synthesis

While lures of plant origin are vital tools in dacine (Diptera: Tephritidae) pest management, the ecological and evolutionary significance of this lure response remains enigmatic. Two hypotheses (the ancestral host hypothesis and sexual selection by female choice) have been invoked to explain the functional significance of these chemicals to dacine fruit flies. These hypotheses are often treated as alternatives to one another and evidence favouring one is used to reject the other. This review highlights that these two hypotheses are not logical alternatives to each other as the ancestral host hypothesis attempts to explain the ultimate function of the response of Dacinae to these plant-derived parapheromones while the sexual selection hypothesis provides a proximate explanation for lure response. Research on lure response, dacine mating behaviour, functional significance of lures, plant phylogeny and biochemistry and dacine pheromone chemistry are used to evaluate the evidence in relation to both these hypotheses. Some of the key findings are that there is evidence both in support of and against these two hypotheses. Response of fruit flies to related phenyl propanoids to those commonly used as lures in pest management and distribution of phenyl propanoids attractive to dacines among plant orders strongly support the ancestral host hypothesis. Evidence from pheromone chemistry, dacine mating behaviour and the functional significance of lures both support and contradict the sexual selection hypothesis. Lures appear to have different proximate functions in different dacine species. Considerably greater research is needed to clarify the functional role of phytochemical lures to dacine fruit flies. The two prevalent hypotheses should be investigated independently. Specific research on dacine phylogeny and distribution of lures in plants in relation to ecological roles played by adult dacines is required to elucidate the ultimate roles of the chemicals. Exploration of female response to lures and the behavioural consequences of dacine response to these chemicals to both the insect and plant may shed light on the proximate functions of these chemicals.     

Effects of energetic reserves on behavioral patterns of Mediterranean fruit flies (Diptera: Tephritidae)

The objective of this study was to associate levels of nutritional reserves (specifically lipids, sugars, and glycogen) in individual Mediterranean fruit flies, Ceratitis capitata (Diptera: Tephritidae), with observed patterns of behavior in the field. We collected females (n=255) and males (n=181) from the field, recording the time of collection and the activity they were engaged in when collected. Subsequently, we employed colorimetric biochemical techniques to determine the precise amounts of lipids, sugars, and glycogen in each individual. Lipid and sugar levels in males varied significantly according to the time of collection and the type of activity. Lipid and sugar levels in females did not vary in this manner. Sugar levels in both males and females were highest during the evening, when most feeding occurs. Males that engaged in sexual signaling in leks during the mid-afternoon had relatively low sugar and high lipid levels. Males engaged in the alternative mating tactic of fruit guarding had relatively high sugar and low lipid contents. Glycogen levels in males were high in the mornings, and a decline in glycogen content was associated with participation in leks; however, female glycogen levels did not vary significantly with time of day or activity. Our results provide quantitative evidence for the role nutrient reserves play in driving patterns of male reproductive behavior, yet suggest that factors other than sugar and lipid reserves constrain female behavior. Received: 8 April 1997 / Accepted: 23 June 1997     

Feeding and foraging of wild and sterile Mediterranean fruit flies (Diptera: Tephritidae) in the presence of spinosad bait

The sterile insect technique (SIT) is used to control wild Mediterranean fruit fly introductions in California and Florida in the U.S. In the past, bait sprays containing malathion proved invaluable in treating new outbreaks or large populations before the use of SIT. Recently, a spinosad protein bait spray, GF-120, has been developed as a possible alternative to malathion, the standard insecticide in protein bait sprays. In this study, protein-deficient and protein-fed Vienna-7 (sterile, mass-reared, "male-only" strain) flies and wild males and females were evaluated to determine the effectiveness of the GF-120 protein bait containing spinosad with respect to bait attraction, feeding, and toxicology. There were no effects of diet or fly type on feeding duration in small laboratory cages. Wild flies, however, registered more feeding events than Vienna-7 males. Flies that fed longer on fresh bait died faster. Protein-deficient flies were more active and found the bait more often than protein-fed flies. Data suggest that adding protein to the diet of SIT flies may decrease their response to baits, therefore, reduce mortality, and thus, allow the concurrent use of SIT and bait sprays in a management or eradication program.