Todd E. Shelly

Male courtship success and female discrimination in the mediterranean fruit fly (Diptera: Tephritidae)

The mating success of individually marked male Mediterranean fruit flies was monitored over 6 consecutive days in the laboratory. Mating frequency was nonrandom, as the numbers of both males that failed to mate and males that mated many (more than four) times were much higher than expected by chance alone. Differential mating success resulted in part from intermale variation in activity level. Male copulatory success was positively correlated with the numbers of courtships performed, attempted copulations (mountings), and females courted. Male-male aggression, on the other hand, and a negligible effect on male mating success. Female choice also appeared to influence male mating frequency. Fewer than 10% of courtships resulted in mating, and in most cases females terminated courtship by simply moving away from the male. Females that did mate generally selected males having higher copulatory scores than previously rejected males.

Exposure to α-Copaene and α-Copaene-Containing Oils Enhances Mating Success of Male Mediterranean Fruit Flies (Diptera: Tephritidae)

Abstract Previous research revealed that exposure to the synthetic attractant trimedlure increased the mating success of male Mediterranean fruit flies, Ceratitis capitata (Wiedemann). In the current study, I investigated whether a similar effect resulted from male exposure to α-copaene, a naturally occurring compound found in many host plants, and two α-copaene-containing essential oils, angelica seed oil (Angelica archangelica L.) and ginger root oil, (Zingiber officinale Roscoe). For all three substances, mature males were exposed to 20 μl of the attractant over a 6-h period and then held 2 d before testing. In field-cage trials, treated males (exposed to attractants) obtained significantly more matings than control males (no exposure) for all three substances. In an additional experiment with ginger root oil, treated males prevented from contacting the oil directly (i.e., exposed to the odor only) still exhibited a mating advantage over control males. Discussion centers on the influence of α-copaene-bearing plants on the mating system of C. capitata and the possibility of using attractants in prerelease exposure of males to increase the effectiveness of sterile insect release programs.

INFLUENCE OF MALE DIET ON MALE MATING SUCCESS AND LONGEVITY AND FEMALE REMATING IN THE MEDITERRANEAN FRUIT FLY (DIPTERA: TEPHRITIDAE) UNDER LABORATORY CONDITIONS

Abstract The purpose of the present study was to investigate the effect of dietary protein on the mating behavior and survival of male Mediterranean fruit flies (medflies), Ceratitis capitata (Wied.), as a means of enhancing the effectiveness of mass-reared males in sterile release programs to suppress wild populations. Conducted in the laboratory, our study addressed three main questions: 1) Does the inclusion of protein in the adult diet affect mating success of wild and mass-reared males? 2) Are copulation duration and remating tendency of wild females affected by the strain (wild versus mass-reared) and diet (protein-fed versus protein-deprived) of their initial mating partner? 3) Does the inclusion of protein in the adult diet affect the longevity of mass-reared males? In mating trials involving wild flies, protein-fed males had a mating advantage over protein-deprived males. However, the addition of protein to the diet did not boost the mating success of mass-reared males in competition with wild or mass-reared males for wild females. The inclusion of protein in the male diet had no apparent effect on female remating tendency, copulation duration, or male longevity. Independent of male diet, we found no difference between wild and mass-reared males in the duration of copulations with wild females, and wild females mated initially to wild and mass-reared males displayed similar remating propensity. The implications of these findings for SIT are discussed.

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

Abstract 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 (≈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.

Alternative mating strategies in a desert grasshopper: evidence of density-dependence

Field observations revealed that, on a given day, male mating behaviour in a population of the grasshopper Ligurotettix coquilletti ranged from little or no stridulation (inactive) to relatively persistent singing (active signalling). Inactive males were usually located in the territories of active signallers. Actively signalling male achieved more matings, and also more frequently approached and mounted females in incidents terminating in the male departing the female without copulating. Individuals switched between inactive and actively-signalling behaviour during their adult lives, and males that were usually active signallers achieved greater lifetime mating success. Thus, we obtained no evidence to support the hypothesis that variation in mating behaviour was maintained by negative frequency-dependent selection. By comparing the behaviour of males in two field plots maintained at different population densities, however, we found that high density was directly related to a higher incidence of inactive behaviour. Males perched on creosote (Larrea tridentata) bushes (their host plant), and certain bushes. Mating behaviour was independent of body size and, while young (<7 days old) males tended to be inactive, neither age nor the time of adult maturation during the season could fully account for the incidence of inactive behaviour among males. Instead, we suggest that the adoption of inactive behaviour resulted partly from aggressive encounters between males.

Acquisition of female-attracting fragrance by males of oriental fruit fly from a Hawaiian Lei flower, Fagraea berteriana

Males of the Oriental fruit fly, Bactrocera dorsalis, are strongly attracted to and compulsively feed on a fragrant lei flower, Fagraea berteriana. A series of phenylpropanoid components, trans-3,4-dimethoxycinnamyl alcohol, its acetate, and trans-3,4-dimethoxycinnamaldehyde were characterized as male attractants. The alcohol stimulated the same level of feeding activity as methyl eugenol. Males that fed on flowers selectively converted the attractant components into trans-coniferyl alcohol and stored it in rectal glands. Males scented with the phenylpropanoids were more successful in mating than unfed males, indicating the advantage of acquiring the fragrance in mating success.

Flower-feeding affects mating performance in male oriental fruit flies Bactrocera dorsalis

1. Males of the oriental fruit fly Bactrocera dorsalis are attracted to and feed on flowers of the golden shower blossom Cassia fistula. Flowers of this plant contain methyl eugenol, the metabolites of which apparently function in the synthesis of male sex pheromone.

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

Abstract Previous research revealed that exposure to ginger root oil, Zingiber officinale Roscoe, containing the known male attractant (α-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 μl 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 ≈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.

INFLUENCE OF ADULT DIET ON THE MATING SUCCESS AND SURVIVAL OF MALE MEDITERRANEAN FRUIT FLIES (DIPTERA: TEPHRITIDAE) FROM TWO MASS-REARING STRAINS ON FIELD-CAGED HOST TREES

Abstract Using field-caged host trees, this study investigated the influence of adult diet on the mating success and survival of male Mediterranean fruit flies, Ceratitis capitata (Wied.), from two mass-rearing strains. Upon emergence, males from a genetic sexing (temperature sensitive lethal) strain and a bisexual strain were given either a sugar-protein diet (protein-fed) or a sugar-only diet (protein-deprived). Mating trials were conducted using field-caged host trees, and 100 males of a given strain and diet competed with 100 wild males for matings with 100 wild females (all wild flies were given the sugar-protein diet). There was no apparent effect of diet on male mating success for either mass-reared strain. Wild males obtained significantly more matings per replicate than males from either strain on either diet, and the mean number of matings per replicate was similar between protein-fed and protein-deprived males for both strains. In addition, the survival of protein-fed and protein-deprived males was compared over 2- and 4-day intervals on field-caged host trees. Within each mass-reared strain, there was no apparent effect of adult diet on male survival for either test interval. The present findings are compared with similar studies on other mass-reared strains.

Lek behaviour of a Hawaiian Drosophila: male spacing, aggression and female visitation

Abstract Male spacing, aggression and female visitation are described for a large lek of Drosophila confirmis within a mid-elevation rain forest on the island of Hawaii. The lek was located at a single tree of Pisonia umbellifera, and most of the males present defended individual leaves as mating territories. Regular censuses over a 3-week period in April 1985, revealed that the frequency with which males occupied a given leaf was unrelated to either the size or the orientation of the leaf but was related to its height above ground, lower leaves being occupied more frequently than higher leaves. During most censuses, 10–20% of the males were found perching on branches near lower leaves, which they invaded frequently. Males engaged in two types of aggressive interactions, chases and grapples, and both types occurred more frequently on lower leaves than on higher leaves. Both the spacing of males and the outcome of aggressive interactions were strongly size-dependent; larger males tended to occupy the lower leaves nd chase smaller males. Females were observed at the lek only infrequently and only during the middle of the day; between 1000 and 1500 hours, females were sighted approximately once an hour. Most of the leaves visited by females were among the lowest at the lek, and five of the six matings observed occurred on lower leaves. Data regarding male abundance and position and female visitation were also collected at the same lek site in October 1985, and are compared with the findings from April.