Consumption of β-Caryophyllene Increases the Mating Success of Bactrocera zonata Males (Diptera: Tephritidae)

The peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae), is an economically important polyphagous quarantine pest of horticultural crops endemic to South and Southeast Asia. Methyl eugenol (ME), a naturally occurring phenylpropanoid, is a male attractant used to lure and (when mixed with an insecticide) annihilate the males from the wild population, a method of pest control termed the male annihilation technique (MAT). ME is reported to enhance the mating success of sterile males of Bactrocera spp., which is critical for enhancing the effectiveness of the sterile insect technique (SIT). The suppressed response of ME-treated males to ME-baited traps/devices allows the simultaneous application of the MAT and SIT, increasing the efficiency of area-wide integrated pest management (AW-IPM) programs. However, ME treatment in sterile males in SIT facilities is logistically difficult. β-caryophyllene (BCP) is a widely occurring, safer plant compound and is considered suitable for treating males in SIT facilities. Here, we demonstrate that BCP feeding enhanced B. zonata male mating success to the same extent as ME feeding. Feeding on BCP suppressed the male's subsequent attraction to ME-baited traps, but not to the same degree as feeding on ME. The results are discussed and BCP is suggested as an alternative to ME for the concurrent use of the MAT and SIT.

Less is more: Fewer attract-and-kill sites improve the male annihilation technique against Bactrocera dorsalis (Diptera: Tephritidae)

The Male Annihilation Technique (also termed the Male Attraction Technique; "MAT") is often used to eradicate pestiferous tephritid fruit flies, such as Bactrocera dorsalis (Hendel). MAT involves the application of male-specific attractants combined with an insecticide in spots or stations across an area to reduce the male population to such a low level that suppression or eradication is achieved. Currently, implementations of MAT in California and Florida targeting B. dorsalis utilize the male attractant methyl eugenol (ME) accompanied with a toxicant, such as spinosad, mixed into a waxy, inert emulsion STATIC ME (termed here "SPLAT-MAT-ME"). While highly effective against ME-responding species, such applications are expensive owing largely to the high cost of the carrier matrix and labor for application. Until recently the accepted protocol called for the application of approximately 230 SPLAT-MAT-ME spots per km2; however, findings from Hawaii suggest a lower density may be more effective. The present study adopted the methods of that earlier work and estimated kill rates of released B. dorsalis under varying spot densities in areas of California and Florida that have had recent incursions of this invasive species. Specifically, we directly compared trap captures of sterilized marked B. dorsalis males released in different plots under three experimental SPLAT-MAT-ME densities (50, 110, and 230 per km2) in Huntington Beach, CA; Anaheim, CA; and Sarasota-Bradenton, FL. The plots with a density of 110 sites per km2 had a significantly higher recapture proportion than plots with 50 or 230 sites per km2. This result suggests that large amounts of male attractant may reduce the ability of males to locate the source of the odor, thus lowering kill rates and the effectiveness of eradication efforts. Eradication programs would directly benefit from reduced costs and improved eradication effectiveness by reducing the application density of SPLAT-MAT-ME.

Methyl eugenol aromatherapy: a delivery system facilitating the simultaneous application of male annihilation and sterile insect technique against the peach fruit fly

BACKGROUND

The peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae) is an economically important polyphagous, quarantine pest endemic to South and South-East Asia. The male annihilation technique (MAT) and the sterile insect technique (SIT) are environmentally benign techniques used to suppress fruit fly populations on an area-wide basis. The MAT and SIT are typically used sequentially to avoid killing released sterile males; however, MAT and SIT potentially could be used simultaneously and thereby increase the overall efficiency of control programmes. Mating competitiveness of sterile males against wild counterparts is critical for the success of the SIT. Feeding on a semiochemical, methyl eugenol (ME) has been reported to enhance the male mating performance of many Bactrocera spp., including B. zonata, but its use in SIT operational programmes is limited owing to the absence of a viable delivery system.

RESULTS

In the present study, we demonstrated that ME aromatherapy, a practical method for large-scale delivery of ME olfactorily, enhances the mating success of treated B. zonata males. ME aromatherapy application to 5-day-old immature males for a duration of 5 h resulted in increased mating success of males tested when sexually mature, compared to untreated males. The ME-aromatized males also exhibited reduced attraction to ME-lure.

CONCLUSION

A practical delivery system for applying ME by aromatherapy to mass-reared males was developed. ME-aromatherapy enhanced male mating success and suppressed their subsequent attraction to ME, thus enabling the application of MAT and SIT at the same time. © 2023 Society of Chemical Industry.

Weathering of 3-component synthetic food cones: effects on residual amount, release rate, and field capture of 3 pest species of fruit flies (Diptera: Tephritidae)

Food-based baits are an important component of trapping networks designed to detect invasive tephritid fruit flies (Diptera: Tephritidae). An aqueous solution of torula yeast plus borax (TYB) is widely used, but synthetic food lures have been developed to facilitate field procedures, ensure standard composition, and lengthen the interval of bait attractiveness. Cone-shaped dispensers, containing ammonium acetate, putrescine, and trimethylamine (so-called 3C food cones), are currently being used in some large-scale trapping systems (e.g., Florida). Prior work in Hawaii showed that traps baited with 3C food cones capture similar numbers of Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), as TYB-baited traps after 1-2 wk of weathering but capture fewer medflies thereafter. In addition, 3C food cones attract fewer oriental fruit flies, Bactrocera dorsalis (Hendel), and melon flies, Zeugodacuscucurbitae (Coquillett) than TYB even when the food cones are freshly deployed. The current study describes an additional trapping experiment that expands upon earlier work by (i) presenting 3C food cones either unbagged (as done previously) or in nonporous or breathable bags to possibly reduce volatilization and lengthen bait effectiveness and (ii) measuring the content of the 3 components over time to potentially associate fruit fly captures with the loss of these food cone constituents. Implications of these findings for fruit fly surveillance programs are discussed.

Mating Competitiveness of Bactrocera dorsalis (Diptera: Tephritidae) Males From a Genetic Sexing Strain: Effects of Overflooding Ratio and Released Females

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a global pest that infests a range of fruit and vegetables. Males are attracted to methyl eugenol, and control is often achieved by the Male Annihilation Technique, where methyl eugenol + insecticide dispensers are deployed to eliminate males, preclude matings, and reduce population growth. The Sterile Insect Technique (SIT) has also been used to control B. dorsalis. The SIT involves the release of mass-reared, sterilized males to achieve matings with wild females, who then produce inviable eggs. Two key elements of SIT include the overflooding ratio achieved (sterile: wild males) and the strain type utilized, namely bisexual or genetically sexed (allowing male-only releases). Here, we describe the effects of these two factors on the mating competitiveness of a males from a genetic sexing strain of B. dorsalis, termed DTWP. Mating success was scored for DTWP versus wild males in field cages at ratios of 1:2, 1:1, 2:1, and 10:1 both when DTWP females were or were not concurrently released with DTWP males. Close correspondence was found between observed numbers of matings of particular male-female combinations and expected numbers based on the numbers of flies released of each sex and each strain. As a result, the proportion of total matings achieved by the DTWP across the eight treatments showed a corresponding increase with overflooding ratio. At a given ratio, DTWP males had a higher relative mating success when DTWP females were absent rather than present, although the reason for this was unclear.

Evaluation of a Genetic Sexing Strain of the Oriental Fruit Fly as a Candidate for Simultaneous Application of Male Annihilation and Sterile Insect Techniques (Diptera: Tephritidae)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is an important pest of fruits and vegetables, and many countries operate surveillance programs to detect infestations and, if needed, implement costly control efforts. The Male Annihilation Technique (MAT), which involves deployment of the male lure methyl eugenol (ME) to reduce or eliminate the male population, has been used as a stand-alone strategy or as a precursor to the Sterile Insect Technique (SIT), which involves the release of sterile males to generate sterile male by wild female crosses and the production of inviable progeny. Modeling suggests that simultaneous implementation of MAT and SIT, rather than sequential deployment, increases the probability of successful eradication. Previous research has shown that B. dorsalis males that have fed on ME show reduced tendency to re-visit ME sources. Also, males fed ME gain a mating advantage over nonfed males. The goal of the present study was to evaluate the suitability of a genetic sexing strain of B. dorsalis as a candidate for concurrent implementation of MAT and SIT. Evaluation focused on the timing of prerelease exposure to methyl eugenol to identify the male age at which feeding upon the lure both i) reduces postrelease attraction to ME-baited traps (thus allowing the operation of MAT) and ii) enhances postrelease mating competitiveness (thus increasing the effectiveness of SIT). Results indicate that prerelease ME feeding by 6-d-old males, with release the following day, would allow effective, concurrent implementation of MAT and SIT.

Mate choice confers direct benefits to females of Anastrepha fraterculus (Diptera: Tephritidae)

Exposure to plant compounds and analogues of juvenile hormone (JH) increase male mating success in several species of tephritid fruit flies. Most of these species exhibit a lek mating system, characterized by active female choice. Although the pattern of enhanced male mating success is evident, few studies have investigated what benefits, if any, females gain via choice of exposed males in the lek mating system. In the South American fruit fly, Anastrepha fraterculus, females mate preferentially with males that were exposed to volatiles released by guava fruit or treated with methoprene (a JH analogue). Here, we tested the hypothesis that female choice confers direct fitness benefits in terms of fecundity and fertility. We first carried out mate choice experiments presenting females with males treated and non-treated with guava volatiles or, alternatively, treated and non-treated with methoprene. After we confirmed female preference for treated males, we compared the fecundity and fertility between females mated with treated males and non-treated ones. We found that A. fraterculus females that mated with males exposed to guava volatiles showed higher fecundity than females mated to non-exposed males. On the other hand, females that mated methoprene-treated males showed no evidence of direct benefits. Our findings represent the first evidence of a direct benefit associated to female preference for males that were exposed to host fruit odors in tephritid fruit flies. Differences between the two treatments are discussed in evolutionary and pest management terms.

Terminalia Larval Host Fruit Reduces the Response of Bactrocera dorsalis (Diptera: Tephritidae) Adults to the Male Lure Methyl Eugenol

Methyl eugenol (ME) is a powerful semiochemical attractant to males of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), and is the keystone of detection, control, and eradication programs against this polyphagous and highly invasive tephritid pest. Despite its status as a model lure against B. dorsalis, variation among individuals in their attraction is known, independent of the generally increasing attraction with age and decreases with previous exposure. Here we report that adult male B. dorsalis that fed on Terminalia catappa L. (Myrtales: Combretaceae) (tropical almond) fruit as larvae have a significantly lower behavioral response to ME compared with wild males from Psidium guajava L. (Myrtales: Myrtaceae) or colony-reared males raised on artificial larval diet. F1 males from the tropical almond stock reared on artificial larval diet did not show reduced attraction to ME, suggesting that the lowered response of parental males (sires) results from the host fruit itself, perhaps its relatively high amount of ME. Experiments with ME added to artificial diet lend some support to this interpretation. In addition to the results above, we report on quantities of ME in three different host fruits (T. catappa, P. guajava, and Carica papaya L. (Brassicales: Caricaceae)) of B. dorsalis. This study indicates the need for further research on the effect of host fruit on adult response to lures in economically important tephritids.

Sexual Selection on Leks: A Fruit Fly Primer

Lek mating systems are relatively rare but occur in a diverse taxonomic array of animals, including birds, mammals, anurans, and insects. Such systems exhibit four features: 1) males provide no parental care and supply only gametes; 2) males are spatially aggregated at mating arenas (or leks); 3) males do not control access to resources critical to females; and 4) females are free to select mates at the arena. Among insects, fruit flies of the families Tephritidae and Drosophilidae display lek behavior that closely resembles the 'classic' lek mating systems of vertebrate species. The objective of this paper is to provide an overview of empirical findings on lek-forming tephritid and drosophilid flies. The essay is organized around a series of 19 questions, the first six of which provide background information on fruit fly leks. These questions deal with the location, persistence, and size of leks as well as pheromonal attraction of females and the nature of male-male aggression. The remaining questions touch on broader issues that are common to the study of lekking species regardless of taxonomic affiliation. For example, these questions concern skewed mating distributions among males, male signals important in female choice, the importance of male aggression and signaling position in affecting male mating success, the possibility of male choice, costs to males associated with lek displays, and evidence of direct and indirect benefits to females resulting from mate selection etc. Reflecting data availability, emphasis is on precopulatory mate choice, sperm competition and female cryptic choice are briefly addressed.

Optimizing methyl-eugenol aromatherapy to maximize posttreatment effects to enhance mating competitiveness of male Bactrocera carambolae (Diptera: Tephritidae)

Methyl-eugenol (ME) (1,2-dimethoxy-4-(2-propenyl)benzene), a natural phytochemical, did enhance male Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae) mating competitiveness 3 d after ingestion. Enhanced male mating competitiveness can significantly increase the effectiveness of the sterile insect technique (SIT). ME application to mass reared sterile flies by feeding is infeasible. ME application by aromatherapy however, would be a very practical way of ME application in fly emergence and release facilities. This approach was shown to enhance mating competitiveness of B. carambolae 3 d posttreatment (DPT). Despite this added benefit, every additional day of delaying release will reduce sterile fly quality and will add cost to SIT application. The present study was planned to assess the effects of ME-aromatherapy on male B. carambolae mating competitiveness 1DPT and 2DPT. ME aromatherapy 1DPT or 2DPT did enhance mating competitiveness of B. carambolae males whereas ME feeding 1DPT and 2DPT did not. Male mating competitiveness was enhanced by the ME aromatherapy irrespective if they received 1DPT, 2DPT or 3DPT. ME aromatherapy, being a viable approach for its application, did enhance mating competitiveness of male B. carambolae 1 d posttreatment as ME feeding did 3 d after ingestion.

Methyl eugenol aromatherapy enhances the mating competitiveness of male Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae)

Males of Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae) are strongly attracted to methyl eugenol (ME) (1,2-dimethoxy-4-(2-propenyl)benzene), a natural compound occurring in variety of plant species. ME-feeding is known to enhance male B. carambolae mating competitiveness 3 days after feeding. Enhanced male mating competitiveness due to ME-feeding can increase the effectiveness of sterile insect technique (SIT) manifolds. However, the common methods for emergence and holding fruit flies prior to field releases do not allow the inclusion of any ME feeding treatment after fly emergence. Therefore this study was planned to assess the effects of ME-aromatherapy in comparison with ME feeding on male B. carambolae mating competitiveness as aromatherapy is pragmatic for fruit flies emergence and holding facilities. Effects of ME application by feeding or by aromatherapy for enhanced mating competitiveness were evaluated 3d after treatments in field cages. ME feeding and ME aromatherapy enhanced male mating competitiveness as compared to untreated males. Males treated with ME either by feeding or by aromatherapy showed similar mating success but mating success was significantly higher than that of untreated males. The results are discussed in the context of application of ME by aromatherapy as a pragmatic approach in a mass-rearing facility and its implications for effectiveness of SIT.

Pre-release consumption of methyl eugenol increases the mating competitiveness of sterile males of the oriental fruit fly, Bactrocera dorsalis, in large field enclosures

The sterile insect technique may be implemented to control populations of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), when environmental concerns preclude widespread use of chemical attractants or toxicants. The goal of the present study was to evaluate whether the mating competitiveness of sterile B. dorsalis males could be increased via pre-release feeding on methyl eugenol. Males of the oriental fruit fly are strongly attracted to this plant-borne compound, which they ingest and use in the synthesis of the sex pheromone. Previous studies conducted in the laboratory and small field-cages have shown that males given methyl eugenol produce a more attractive pheromone for females and have a higher mating success rate than males denied methyl eugenol. Here, levels of egg sterility were compared following the release of wild-like flies and either methyl eugenol-fed (treated) or methyl eugenol-deprived (control) sterile males in large field enclosures at four over flooding ratios ranging from 5:1 to 60:1 (sterile: wild-like males). Treated sterile males were fed methyl eugenol for 1-4 h (depending on the over flooding ratio tested) 3 d prior to release. Eggs were dissected from introduced fruits (apples), incubated in the laboratory, and scored for hatch rate. The effect of methyl eugenol was most pronounced at lower over flooding ratios. At the 5:1 and 10:1 over flooding ratios, the level of egg sterility observed for treated, sterile males was significantly greater than that observed for control, sterile males. In addition, the incidence of egg sterility reported for treated sterile males at these lower over flooding ratios was similar to that noted for treated or control sterile males at the 30:1 or 60:1 over flooding ratios. This latter result, in particular, suggests that pre-release feeding on methyl eugenol allows for a reduction in the number of sterile flies that are produced and released, thus increasing the cost-effectiveness of the sterile insect technique.

Recent advances in methyl eugenol and cue-lure technologies for fruit fly detection, monitoring, and control in Hawaii

Worldwide, an important aspect of invasive insect pest management is more effective, safer detection and control systems. Phenyl propanoids are attractive to numerous species of Dacinae fruit flies. Methyl eugenol (ME) (4-allyl-1, 2-dimethoxybenzene-carboxylate), cue-lure (C-L) (4-(p-acetoxyphenyl)-2-butanone), and raspberry ketone (RK) (4-(p-hydroxyphenyl)-2-butanone) are powerful male-specific lures. Most evidence suggests a role of ME and C-L/RK in pheromone synthesis and mate attraction. ME and C-L/RK are used in current fruit fly programs for detection, monitoring, and control. During the Hawaii Area-Wide Pest Management Program in the interest of worker safety and convenience, liquid C-L/ME and insecticide (i.e., naled and malathion) mixtures were replaced with solid lures and insecticides. Similarly, Male Annihilation Technique (MAT) with a sprayable Specialized Pheromone and Lure Application Technology (SPLAT), in combination with ME (against Bactrocera dorsalis, oriental fruit fly) or C-L/RK (against B. cucurbitae, melon fly), and the reduced-risk insecticide, spinosad, was developed for area-wide suppression of fruit flies. The nontarget effects of ME and C-L/RK to native invertebrates were examined. Although weak attractiveness was recorded to flower-visiting insects, including bees and syrphid flies, by ME, effects to native Drosophila and other Hawaiian endemics were found to be minimal. These results suggested that the majority of previously published records, including those of endemic Drosophilidae, were actually for attraction to dead flies inside fruit fly traps. Endemic insect attraction was not an issue with C-L/RK, because B. cucurbitae were rarely found in endemic environments.

Age-dependent variation in mating success of sterile male Mediterranean fruit flies (Diptera: Tephritidae): implications for sterile insect technique

The sterile insect technique (SIT) is widely used in integrated programs against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Unfortunately, the mass-rearing procedures inherent to the SIT often lead to a reduction in the mating ability of the released males. To counter this deficiency, SIT programs rely upon the production and release of large numbers of sterile males to achieve high overflooding (sterile:wild male) ratios. To ensure a high release volume, emergence facilities release adult males at a young age (2 d old in some cases). The primary objective of this study was to describe age-dependent variation in the mating propensity and competitiveness of sterile males of C. capitata. Males that were 2 or 3 d old had lower mating propensity than males that were > or =4 d old, and 3-d-old males had lower mating competitiveness than males that were > or =4 d old. Given these results, we measured the effect of a longer holding period on male mortality in storage boxes. With delayed food placement, males held in storage boxes for 4 d after emergence showed no higher mortality than males held for only 2 d (the standard interval). Using large field enclosures, we compared the levels of egg sterility attained via releases of 2- versus 4-d-old sterile males at two overflooding ratios (5:1 and 100:1). At the lower ratio, the proportion of unhatched eggs observed for trials involving 2-d-old sterile males was not, on average, significantly higher than that observed for matings between wild flies (33 versus 25%, respectively), whereas the level of egg sterility observed for releases of 4 d old sterile males was 62%. At the 100:1 overflooding ratio, the proportion of unhatched eggs associated with the 2-d-old sterile males was 58%, a level not significantly different from that induced by 4-d-old sterile males at the 5:1 ratio and significantly lower than the level (79%) observed for 4-d-old sterile males at 100:1 overflooding ratio. The implications of these results for SIT are discussed.

Sterile insect technique and Mediterranean fruit fly (Diptera: Tephritidae): assessing the utility of aromatherapy in a Hawaiian coffee field

The sterile insect technique (SIT) is widely used in integrated programs against tephritid fruit fly pests, particularly the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Unfortunately, the mass-rearing procedures inherent to the SIT often lead to a reduction in the mating ability of the released males. One potential solution involves the prerelease exposure of males to particular attractants. In particular, exposure of male Mediterranean fruit flies to ginger, Zingiber officinale Roscoe, root oil (GRO) has been shown to increase mating success in laboratory and field cage trials. Here, we describe a field experiment that compares the level of egg sterility observed in two Hawaiian coffee, Coffea arabica L., plots, with GRO-exposed, sterile males released in one (treated) plot and nonexposed, sterile males released in the other (control) plot. Once per week in both plots over a 13-wk period, sterile males were released, trap captures were scored to estimate relative abundance of sterile and wild males, and coffee berries were collected and dissected in the laboratory to estimate the incidence of unhatched (sterile) eggs. Data on wild fly abundance and the natural rate of egg hatch also were collected in a remote area that received no sterile males. Despite that sterile:wild male ratios were significantly lower in the treated plot than in the control plot, the incidence of sterile eggs was significantly higher in the treated plot than in the control plot. Correspondingly, significantly higher values of Fried's competitiveness index (C) were found, on average, for treated than control sterile males. This study is the first to identify an association between the GRO "status" of sterile males and the incidence of egg sterility in the field and suggests that prerelease, GRO exposure may represent a simple and inexpensive means to increase the effectiveness of Mediterranean fruit fly SIT programs.

Effects of the olfactory environment and nutrition on the ability of male Mediterranean fruit flies to endure starvation

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is targeted for control using the sterile insect technique (SIT). For this technique to succeed, released males must be able to compete with wild males for copulations. Male success is mediated by survival in the field often in adverse conditions. Manipulation of the postteneral environment experienced by sterile males before release has been shown to affect male sexual success and survival. The objectives of this study were to determine how various diets, combined with exposure to volatiles containing alpha-copaene, affect the ability of male Mediterranean fruit flies (from a wild and two unisexual strains) to withstand starvation. Accordingly, we maintained males on one of eight regimes combing a diet of either sugar, sugar and protein, a protein pulse or apricot, with or without the aroma of the sexual stimulant alpha-copaene. The apricot diet was associated with the lowest ability to resist starvation. The sugar-only diet was associated with the highest ability to resist starvation by sterile males. Exposure to alpha-copaene, in combination with the apricot diet, had a significant negative effect on the ability of males (from all strains) to resist starvation relative to other regimes examined. We conclude that the holding regimes that elicit the best sexual performance from males paradoxically also hasten their demise, probably by initiating an irreversible metabolic cascade. The search for the optimal prerelease regime continues.

Effect of probiotic adult diets on fitness components of sterile male Mediterranean fruit flies (Diptera: Tephritidae) under laboratory and field cage conditions

The aim of the current study was to investigate the effect of probiotic adult diets, i.e., adult diets containing viable symbiotic intestinal bacteria, on the pheromone-calling activity, mating success, life expectancy, and survival of mass-reared male Mediterranean fruit flies, Ceratitis capitata (Wiedemann), as an avenue for improving the field performance of sterile males in release programs to eradicate, suppress, or prevent spread of wild populations. The effect of inoculation of two standard adult diets (sugar-yeast granulate [SY] and sugar agar [s]) and two experimental formulations (yeast-reduced granulate [Sy] and yeast-enhanced sugar agar [sy]) with Enterobacter agglomerans and Klebsiella pneumoniae (typically occurring in the gut of wild flies) on the different fitness components was assessed in the laboratory and on field-caged host trees. We found that, in the laboratory, males reared on the probiotic yeast-enhanced agar, sy, had a significant mating advantage over competitors fed the standard s agar (probiotic and control) or noninoculated sy agar; no effect of probiotic enrichment (or lowering the yeast content) was found with the granular diets. Mating test results obtained in the field were inconsistent with laboratory data in that no differences in the numbers of matings were observed between males reared on any of the probiotic and control agar diets (or the SY granulate), whereas males feeding on the probiotic modified granulate, Sy, scored significantly more matings than their control competitors. The pheromone-calling activity of males maintained on the granular diets was not affected by probiotic enrichment on any of the seven observation days. Agar-fed males, however, "called" more frequently on days 6 and 7 (but not on days 1-5) when their diet contained the probiotic load. Laboratory survival of granulate-fed males was found to be significantly prolonged with probiotic inoculation and lowering the yeast content of the standard SY granulate (but not with probiotic inoculation of sy). Similarly, males reared on the probiotic and control modified agars (sy) survived significantly longer than those feeding on the standard s agars (inoculated and control). Again, the results obtained in the field were inconsistent, because no differences between treated and control males were found for any of the diets. The findings are discussed in the light of other published studies on adult nutrition and behavioral ecology in C. capitata.

Aromatherapy in the Mediterranean fruit fly (Diptera: Tephritidae): sterile males exposed to ginger root oil in prerelease storage boxes display increased mating competitiveness in field-cage trials

Previous research showed that exposure to ginger root, Zingiber officinale Roscoe, oil increased the mating success of mass-reared, sterile males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This work, however, involved the exposure of small groups of males (n = 25) in small containers (volume 400 ml). Several sterile male release programs use plastic adult rearing containers (so-called PARC boxes; hereafter termed storage boxes; 0.48 by 0.60 by 0.33 m) to hold mature pupae and newly emerged adults before release (approximately = 36,000 flies per box). The objective of the current study was to determine whether the application of ginger root oil to individual storage boxes increases the mating competitiveness of sterile C. capitata males. Irradiated pupae were placed in storage boxes 2 d before adult emergence, and in the initial experiment (adult exposure) ginger root oil was applied 5 d later (i.e., 3 d after peak adult emergence) for 24 h at doses of 0.0625, 0.25, 0.5, 1.0, and 2.0 ml. In a second experiment (pupal-adult exposure), ginger root oil was applied to storage boxes immediately after pupal placement and left for 6 d (i.e., 4 d after peak adult emergence) at doses of 0.25 and 1.0 ml. Using field cages, we conducted mating trials in which ginger root oil-exposed (treated) or nonexposed (control) sterile males competed against wild-like males for copulations with wild-like females. After adult exposure, treated males had significantly higher mating success than control males for all doses of ginger root oil, except 2.0 ml. After pupal-adult exposure, treated males had a significantly higher mating success than control males for the 1.0-ml but not the 0.25-ml dose of ginger root oil. The results suggest that ginger root oil can be used in conjunction with prerelease, storage boxes to increase the effectiveness of sterile insect release programs.

Effects of diet, ginger root oil, and elevation on the mating competitiveness of male Mediterranean fruit flies (Diptera: Tephritidae) from a mass-reared, genetic sexing strain in Guatemala

The release of sterile males is a key component of an areawide program to eradicate the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), from Guatemala and southern Mexico. The objective of our study was to assess the effects of adult diet, exposure to ginger root oil (Zingiber officinale Roscoe), and elevation on the mating competitiveness of the sterile males used in an areawide program. Sterile males were maintained on a protein-sugar (protein-fed) or a sugar-only (protein-deprived) diet and were exposed (for 4 h 1 d before testing) or not exposed to ginger root oil. In field-cage trials conducted at a high (1,500 m) and low (700 m) site, we monitored the influence of these treatments on the mating success of sterile males in competition with wild males (reared exclusively on the protein-sugar diet and without ginger root oil exposure) for wild females. Elevation and ginger root oil exposure had significant effects, with sterile males having higher mating success at the low-elevation site and ginger root oil-exposed males having greater success than ginger root oil-deprived males at both sites. Diet did not have a significant overall effect, and its influence varied with elevation (dietary protein seemed to provide an advantage at the high-elevation site but not at the low-elevation site). Possible implications of these findings for eradication programs against the Mediterranean fruit fly are discussed.

Improving male mating competitiveness and survival in the field for medfly, Ceratitis capitata (Diptera: Tephritidae) SIT programs

The success of the sterile insect technique (SIT) depends critically upon mating between released sterilized males and wild females. In Hawaii, improvements in the efficiency of sterile males were attempted on two separate fronts--mating enhancement and survival improvement. In the former, two methods have been investigated--selective breeding and aromatherapy. In the latter, flies which survived in field cages for several days were selected and bred to produce progeny with enhanced survival ability compared to control flies. Regarding mating selection, standard laboratory-reared males that successfully mated with wild females in field cages were allowed to breed. F1 offspring were inbred, then the selection procedure was repeated for four additional cycles. In the aromatherapy procedure, laboratory-reared males were exposed to ginger root oil for several hours 1 day prior to testing in field cages. Compared to controls, the selected flies improved the mating competitiveness of male flies ca. 3-fold, irradiation reduced this increase to ca. 2.5-fold. Exposing the selected, hybrid strain raised the fitness of the lab males to ca. 9-fold that of wild males. In the ongoing survival selection study, we have obtained lines in which the selected males survived ca. 2-fold better than laboratory control males over several days in an outdoor field cage, with food and water provided. The goal is to combine the traits of higher survival and mating ability into a single strain for SIT release.

Exposure to ginger root oil enhances mating success of irradiated, mass-reared males of Mediterranean fruit fly (Diptera: Tephritidae)

Previous research revealed that exposure to ginger root oil, Zingiber officinale Roscoe, containing the known male attractant (a-copaene) increased the mating success of male Mediterranean fruit flies, Ceratitis capitata (Wiedemann), from a newly established laboratory colony. The goal of the current study was to determine whether exposure to ginger root oil likewise enhanced the mating competitiveness of irradiated C. capitata males from a 5-yr-old mass-reared strain. Mating tests were conducted in field cages containing guava trees (Psidium guajava L.) to monitor the mating frequency of irradiated, mass-reared and wild males competing for wild females. In the absence of chemical exposure, wild males outcompeted the mass-reared males and obtained 74% of all matings. However, following exposure to ginger root oil (20 microl for 6 h), the mating frequencies were reversed. Whether exposed as mature (3-d-old) or immature (1-d-old) adults, mass-reared males achieved approximately 75% of all matings in tests conducted 2 or 4 d following exposure, respectively. Irradiated, mass-reared males prevented from contacting the oil directly (i.e., exposed to the odor only for 6 h) still exhibited a mating advantage over wild males. In an additional study, signaling levels and female arrivals were compared between males exposed to ginger root oil and nonexposed males, but no significant differences were detected. The implications of these findings for the sterile insect technique are discussed.

Male signalling and lek attractiveness in the Mediterranean fruit fly

I tested the null hypothesis that females of the Mediterranean fruit fly, Ceratitis capitata, were equally likely to visit leks composed of males with high versus low mating success. In laboratory trials, the observed distribution of matings among males differed significantly from that expected by chance, owing primarily to the higher than expected numbers of individuals with low (mated 0-1 days over 6 consecutive observation days) or high (mated 4 or more days) mating scores. I termed these two groups as 'low' and 'high' maters, respectively. In the field, greater numbers of female sightings were made at artificial leks of high maters than low maters. This result apparently reflected a greater calling propensity among high maters. Slopes of female sightings versus calling level did not differ significantly between leks of low and high maters, suggesting that the observed relationship between calling activity and female sightings was independent of male mating status. Following the same protocol, I conducted a second experiment to examine whether males used the signals of conspecific males to locate lek sites and, if so, whether signal attractiveness varied with male mating ability. Attraction of males to calling conspecifics was far weaker than that observed for females, and over five different trials a total of only seven male sightings were made at any of the established leks. Copyright 2000 The Association for the Study of Animal Behaviour.

Sexual selection in relation to pest-management strategies

The application of principles derived from the sexual selection literature can assist attempts to subvert the normal mating behavior of pests. Sexual selection encompasses both intermale competition for access to females and female choice of mates. It can operate during long-range attraction and short-range courtship, as well as after copulation. We review the major aspects of sexual selection and illustrate their application to pheromonal and SIT pest-management programs. Pheromones are important both in long-range attraction and in close-range mate choice; parapheromones may be very useful in pest management because of their influence on male mating success. Sexual selection theory provides a scheme for studying the normal mating behavior of a pest species and thus determining which attributes of the mass-reared sterile males are critical to their success with wild females. We hope that our review will suggest novel ways of attacking pests as well as encourage behavioral ecologists to study pest species.

Satellites and Transients: Ecological Constraints On Alternative Mating Tactics in Male Grasshoppers

Abstract

Alternative tactics of male mating behaviour, broadly classifiable as "dominant/ territorial" versus "subordinate/non-territorial", have now been described for numerous species. Furthermore, across diverse taxa the mating tactics of subordinate/non-territorial males often appear as one of two distinct types, satellite or transient behaviour. Despite general recognition of this dichotomy, though, little effort has been made to identify the circumstances under which one of these behaviours is adopted over the other. We compared the mating systems of two congeneric species of desert grasshoppers (genus Ligurotettix) to investigate specifically the role of resource dispersion in shaping the behaviour of subordinate males. The utility of the comparative approach derives from two basic similarities between the species: both Ligurotettix coquilletti and Ligurotettix planum feed almost exclusively on a single host plant species, and the majority of males in both species defend individual host plants to gain access to females. However, the two species are associated with host plants that are dispersed very differently; i.e., L. coquilletti encounter a small number of large plants and L. planum a large number of small ones. In L. coquilletti, subordinate males, individuals noted by their lack of success in aggression and in obtaining matings, were characterized as satellites that remained silent on host plants defended by territorial males. Subordinate males in L. planum, however, were transients that sang regularly but moved frequently among different host plants. We propose that this behavioural discrepancy results from (1) the large difference between the number of potential female encounter sites (i.e., individual host plants) available to the males of the two species and (2) the large difference between the sizes of resource patches defended by the two species, which influences the ability of dominant males to eject subordinates.

Ecological comparisons of robber fly species (Diptera: Asilidae) coexisting in a neotropical forest

Data regarding seasonal abundance, microhabitat preference, and diet were collected over 3 field seasons for adults of 15 robber fly species on Barro Colorado Island, Panama. The species comprised 2 distinct "thermal guilds"; light-seeking (hereafter LS) species foraged in sunlit areas, while shade-seeking (SS) species foraged only in deep shade. All species were rare during the dry season. During the rainy months, most SS species had flight periods of 2-3 months, and no temporal segregation was apparent. In contrast, most LS species had flight periods of only 4-6 weeks, and a distinct sequence of occurrence was evident during 2 years of censusing. Most SS and LS species displayed a pronounced specificity for perches of a particular substrate type. However, the ranges of perching heights utilized varied considerably among species. Dietary comparisons revealed that mean and maximum prey sizes increased with increasing robber fly size, while minimum prey sizes were constant. Robber fly species <20 mg fed primarily upon nematocerous Diptera, whereas larger species generally fed upon a wide variety of prey types. For each thermal guild, the actual mean overlap for a particular niche dimension was compared to mean overlaps generated by randomly assigning species to thermal guilds. No significant differences from the random null hypothesis were found for the SS guild. However, niche complementarity between dietary and spatial overlaps and dietary overlap was apparent among the 5 large LS species.