Effects of male nutrition on sperm storage and remating behavior in wild and laboratory Anastrepha fraterculus (Diptera: Tephritidae) females

Male physiological condition can affect his ability to modulate female sexual receptivity. Thus, studying this aspect can have biological and practical implications. Here, we examine how male nutritional status affected the amount of sperm stored, remating rate and refractory period of the tephritid fruit fly Anastrepha fraterculus (Wiedemann) females. Both wild and laboratory flies were evaluated. We also examine female sperm storage patterns. Experiments were carried out by manipulating male adult diet and exposing these males to virgin females. Females mated with differently treated males were either dissected to count the amount of sperm stored or exposed to virgin males to determine remating rate and the length of the refractory period. We found that male nutritional status affected the amount of the sperm stored and the renewal of sexual receptivity in wild flies. For laboratory flies, male nutritional status affected the length of the refractory period but not the amount of sperm stored by females. In addition, we report that the ventral receptacle is not an important organ of sperm storage in this species. We conclude that male nutritional condition influences the ability to modulate female sexual receptivity, possibly through a combination of the quantity and quality of the ejaculate. From an applied perspective, providing males with an enriched diet will likely result in increased efficacy of the sterile insect technique.     

Calling behavior of mass-reared and wild Anastrepha serpentina (Diptera: Tephritidae)

The calling behavior of mass-reared and wild males of Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) was studied both in the laboratory and in field cage tests. In the laboratory, density (1, 5, and 10 males per container), age, and hour of day significantly affected calling behavior. Mass-reared males called independently of density, whereas wild males only called at densities of 5 and 10 individuals. Males of both strains started calling when they were 5-7 d old. The daily pattern of male calling was similar in both strains, starting at 0730 hours, and reaching a peak at 1330-1630 hours. Field cage tests showed that mass-reared males started calling when they were 5d old; the period of peak calling was when males were 8-9 d old. In contrast, wild males began calling when they were 10 d old, reaching peaks when males were 13, 15, and 18 d old. Wild males tended to form leks to call during each day of the experiment, whereas mass-reared males only formed leks during 2 d, both strains displaying very low levels. During field cage tests, males, independently of strain, displayed two calling peaks, one peak in the morning and one peak in the afternoon, whereas males observed in the laboratory only showed a single calling peak. The results are discussed in view of the effects of mass rearing A. serpentina males in relation to potential use of the sterile insect technique.     

Function of multiple sperm storage organs in female Mediterranean fruit flies (Ceratitis capitata, Diptera: Tephritidae)

Sperm storage organs allow females to temporally separate insemination from fertilization, manipulate ejaculates and control fertilization. In the reproductive tract of female fruit flies (Diptera: Tephritidae), sperm are found in two different organs--a pair or triplet of spermathecae, and a "fertilization chamber". In order to understand the specific function of each of these organs, we tested the following hypotheses: (1) Sperm are distributed equally amongst the various sperm storage organs; (2) Both organ types maintain sperm viability; and (3) Sperm used in fertilization come from the fertilization chamber. We counted sperm in spermathecae and fertilization chamber of Mediterranean fruit flies (Ceratitis capitata) every 3 days for 18 days following insemination, and used a live/dead staining technique to determine the viability of sperm in these organs. Finally, by extirpating spermathecae from inseminated females and allowing them to oviposit, we were able to identify the fertilization chamber as the source of fertilizing sperm. Numbers of sperm in the spermathecae declined from an average of 3575 on the day of copulation to 649, 18 days later. Conversely, the fertilization chamber maintained a fairly constant level of sperms, ranging between an average of 207 cells on day 3 to 115 sperms on day 18. Throughout the period we monitored, we found high levels of sperm viability in both organs (> 80%). Sperm viability was similarly high in the fertilization chambers of females without spermathecae. However, fertility of eggs laid by these females declined rapidly, as did the number of sperm in the fertilization chamber. We conclude that both the spermathecae and the fertilization chamber are active sperm storage organs, with separate functions: the spermathecae for long-term storage and the fertilization chamber, periodically filled by the spermathecae, a staging point for fertilizing sperm. We suggest that the use of both organs by females results in sperm economy, which adaptively prolongs the intervals between copulations.     

Male and female condition influence mating performance and sexual receptivity in two tropical fruit flies (Diptera: Tephritidae) with contrasting life histories

Recent recognition of widespread polyandry in insects has generated considerable interest in understanding why females mate multiple times and in identifying factors that affect mating rate and inhibit female remating. However, little attention has been paid to understanding the question from both a female and male perspective, particularly with respect to factors that may simultaneously influence female remating rates. Here, we report on a study aimed at ascertaining the possible interactive effects that male and female size and diet, and female access to a host could have on mating latency, probability, and duration and female refractory period using two tropical fruit fly species with contrasting life histories. Of all factors tested, adult diet played the most significant role. Both Anastrepha ludens and Anastrepha obliqua males which had constant access to protein and sucrose mated more often, had shorter copulations and induced longer refractory periods in females than males fed a low quality diet (sucrose offered every third day). Female size and the interaction with male diet determined how quickly female A. ludens mated for the first time. Smaller females mated sooner with low quality fed males than with high quality fed males while there was no difference for large females, suggesting that male choice may be at play if high quality fed males discriminate against smaller females. Copulation duration also depended on both male and female nutritional condition, and the interaction between male diet and female size and diet. Large and high quality fed females had shorter copulations regardless of male condition. Importantly, for A. ludens, female refractory period depended on male size and the nutritional condition of both males and females, which could indicate that for this species, female receptivity does not depend only on the condition of the male ejaculate. For A. obliqua refractory period was associated with the interaction between male size and diet and male diet and host presence. We discuss our results in terms of male ability to inhibit female remating and the relative contribution of female condition to this behavior. We also address the importance of studying effects simultaneously on species with contrasting life histories.     

Male diet and age influence to inhibit female remating in Ceratitis capitata (Diptera: Tephritidae)

This study evaluated the influence of age and adult nutritional status of Ceratitis capitata males on their ability to inhibit female remating. Their roles and that of copula duration on the amount of sperm transferred to female spermathecae were also analysed. After emergence, adults were kept in separate groups according to their diets (either high protein – 6.5 g of brewer’s yeast, or low protein – 3.5 g of brewer’s yeast) and their age at the time of use in experiments (4, 8, 12, 16 and 20 days old). The results demonstrated that: (i) male age was not a factor that influenced remating when females mated with well‐nourished males; however, the youngest males (4 days old) in the low‐protein group were less efficient in preventing female remating; (ii) 12‐ and 16‐day‐old males fed on a high‐protein diet transferred and produced more sperm than males of other groups; (iii) there was no correlation between copula duration and the amount of sperm transferred to the female; the longest copula durations were observed among low‐protein‐diet/20‐day‐old males. These results suggest that age and nutrition influence the ability of the males to inhibit female remating. The sterile insect technique is most effective when females do not remate after coupling with sterile males, and therefore, the capacity to inhibit female remating is an important characteristic of males released in the field.     

Host status of grapefruit and Valencia oranges for Anastrepha serpentina and Anastrepha ludens (Diptera: Tephritidae)

Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) is sporadically captured in the Rio Grande Valley of Texas. Although its preferred hosts are in the Sapotaceae family, several varieties of Citrus, including grapefruit and oranges are listed as alternate hosts. Although Mexican fruit fly, Anastrepha ludens (Loew), is known to be a major pest of Citrus, doubt exists as to the status of Citrus as a breeding host for A. serpentina. To evaluate the host status of commercial Citrus for A. serpentina we compared oviposition and development with that of A. ludens under laboratory conditions with 'Rio Red' grapefruit (Citrus paradisi MacFayden) and 'Valencia' oranges [Citrus sinensis (L.) Osbeck] in different stages of maturity. Both fly species oviposited in early season fruit in which the eggs and larvae died in the fruit albedo. Survival of either species to the adult stage occurred in later season grapefruit. In oranges, no A. serpentina larvae survived compared with 150 A. ludens surviving to adults. Survival on both Citrus species was much lower for A. serpentina, only approximately 5% of eggs eclosed into larvae in grapefruit compared with approximatley 50% for A. ludens. In oranges approximately 16% of A. serpentina eggs eclosed compared with approximately 76% for A. ludens. In grapefruit, only one fourth as many A. serpentina larvae survived to the adult stage compared with A. ludens. Additional experiments were performed in a greenhouse on small, caged trees of la coma (Sideroxylon celastrinum H.B.K.), a Texas species of Sapotaceae. The A. serpentina females readily oviposited into these berries and normal adults emerged. The present low incidence of the adults, coupled with the high mortality during development of the larvae, suggests that Texas citrus is unlikely to support a breeding population of A. serpentina.     

Male courtship song in circadian rhythm mutants of Bactrocera cucurbitae (Tephritidae: Diptera)

Pulse train intervals (PTI) of courtship song were differentiated between circadian clock mutants of the melon fly, Bactrocera cucurbitae (Coquillett) (Tephritidae: Diptera). We analysed the male mating song of B. cucurbitae flies of two mutant strains that differed in circadian locomotor rhythm by a LabVIEW programming system. Flies with a short circadian rhythm (S-strain) had shorter PTI than those with a long circadian rhythm (L-strain) in the two age groups tested, young and old. Young flies showed longer PTI than old flies, but no interaction between strain and age was found in PTI. There was a significant interaction between strain and age for pulse train duration (PTD), whereas no stable difference was found in PTD between S- and L-strains. These results suggest a positive correlation between the length of the circadian locomotor rhythm and PTI of courtship song sounds in B. cucurbitae.     

Effect of emergence time on the reproductive parameters of mass-reared Anastrepha ludens (Diptera: Tephritidae) flies

In the mass rearing of fruit flies, the adult emergence time is gradual, due to factors such as variation in food consumption in the larval phase, the female oviposition behavior and environmental conditions, among others. Here, we investigate the effect of emergence time on sex ratio, fecundity, fertility, body size and mating performance in mass-reared Anastrepha ludens (Diptera: Tephritidae) flies. The results of the study indicated that the emergence of the flies is gradual and lasts approximately 96?h, but the highest proportion of emerged flies was observed at 48?h. The flies emerging at 24 and 48?h showed higher fecundity than those emerging at 72 and 96?h, but there were no significant differences in the sex ratio, fertility and male mating performance. Body size was significant, the flies that emerged at 24, 48 and 72?h were bigger than those emerged at 96?h. The discussion focuses on the effect of emergence time on the rearing processes and release of the Mexican fruit fly.     

Effect of Adult Nutrition on Male Sexual Performance in Four Neotropical Fruit Fly Species of the Genus Anastrepha (Diptera: Tephritidae)

Fruit flies (Diptera: Tephritidae) have been used previously as a model to explore the effect of nutrition on male reproduction. Here we tested the hypothesis that adult feeding history influences male sexual performance in four species of neotropical fruit flies of the genus Anastrepha (A. ludens, A. obliqua, A. serpentina, and A. striata), an approach that allowed us to consider species-specific ecological factors independent of phylogenetic constraints. We fed, from the moment of emergence, four experimental groups of males of each species with either (1) dry sucrose, (2) a mixture of dry sucrose and hydrolyzed protein (enzymatic yeast hydrolyzate), (3) a mixture of dry sucrose and bird feces, or (4) an open fruit [Citrus sinensis (orange), Mangifera indica (mango), Manilkara zapota (chico zapote), and Psidium guajava (guava) for A. ludens, A. obliqua, A. serpentina, and A. striata, respectively]. Cohorts of 12-day-old individuals (28 males [7 of each diet treatment] and 14 females) were released simultaneously into species-specific field cages and the following parameters recorded over a 4-day period (procedure repeated with five different cohorts for each species): number of males involved in calling activities every hour (i.e., pheromone emissions, wing fanning, wing motions, or extensions of the mouthparts), identity of copulating males, and copula duration. In the case of A. obliqua, we also observed separately cohorts of 20-day-old individuals. In A. obliqua, A. serpentina, and A. striata, males fed on a protein-supplemented diet had higher copulatory success when competing against males fed on other diets. Anastrepha serpentina and A. striata were sensitive to diet on all but two of the parameters analyzed (i.e., males with consecutive copulas and copula duration in the case of A. serpentina and males with multiple and consecutive copulas in the case of A. striata). In sharp contrast to this, the male mating performance of A. ludens was not affected by diet. Anastrepha obliqua was sensitive to different parameters depending on age. We discuss our findings and their sexual selection implications in light of each species' habits.     

Prolonged mating in the melon fly,Dacus cucurbitae (Diptera: Tephritidae): Competition for fertilization by sperm-loading

Summary Males of the melon flyDacus cucurbitae mate with females for 10 hours or more, usually starting at dawn and terminating at dusk. We tested the sperm-loading hypothesis (Dickinson, 1986) that males remaining with females for long periods of time benefit by numerically overwhelming the sperm of their competitors. The amount of sperm transferred to a female increased with time after mounting. The number of feamles which laid eggs at least once during experimental periods was positively correlated with mating duration. Oviposition rate was positively correlated with mating duration, as well. Egg hatchability was not influenced by mating duration. Mating duration was a major determinant of paternity when females were doubly mated with one male for 6 hours and another male for 2 hours. Females whose first matings were longer showed first male sperm predominance, while females whose second matings were longer showed last male sperm predominance. The adaptive significance of prolonged mating by male melon flies is discussed.     

Nonhost status of commercial Persea americana 'Hass' to Anastrepha ludens, Anastrepha obliqua, Anastrepha serpentina, and Anastrepha striata (Diptera: Tephritidae) in Mexico

The objective of this study was to determine the host status in Mexico of commercially cultivated and marketed avocado, Persea americana (Mill.), 'Hass' to Anastrepha ludens (Loew), Anastrepha obliqua (Macquart), Anastrepha serpentina (Wiedemann), and Anastrepha striata (Schiner) (Diptera: Tephritidae). Experiments in Michoacán, Mexico, were carried out in six orchards located at three altitudes above sea level during two times (August-October 2001 and April-June 2002). They included choice ('Hass' avocado plus natural host) and no-choice foraging behavior tests on trees under field cages; no-choice, forced infestation trials on caged, fruit-bearing branches in the field, and with individual fruit under laboratory conditions; infestation trials using 'Hass' avocados left unprotected over 1 and 7 d on the ground of orchards; studies to ascertain depth of oviposition and determine egg hatchability; and experiments to determine susceptibility by using time elapsed since removal of fruit from tree as the experimental variable. We trapped adult Anastrepha (n = 7,936) in all orchards and dissected fruit (n = 7,695) from orchards and packing houses (n = 1,620) in search of eggs or larvae. Most (96.7%) A. ludens, A. obliqua, A. striata, and A. serpentina adults were captured in low-elevation orchards. No eggs or larvae were detected in any of the fruit from foraging behavior studies or dissected fruit from orchards or packing houses. Of 5,200 mature, intact fruit on trees in the field forcibly exposed to no-choice female oviposition activity (five females/fruit), we only found four fruit infested by A. ludens but no adults emerged. 'Hass' avocados only became marginally susceptible to attack by A. ludens (but not A. obliqua, A. serpentina, and A. striata) 24 h after being removed from the tree. Fruit placed on the ground in orchards (n = 3,600) were occasionally infested by Neosilba batesi (Curran) (Diptera: Lonchaeidae), a decomposer, but not Anastrepha spp. Based on our results, commercially cultivated and marketed P. americana 'Hass' should not be considered a natural host of A. ludens, A. obliqua, A. striata, and A. serpentina in Mexico.     

Wolbachia in Anastrepha Fruit Flies (Diptera: Tephritidae)

Endosymbiotic bacteria of the genus Wolbachia are widespread among arthropods and cause a variety of reproductive abnormalities, such as cytoplasmic incompatibility, thelytokous parthenogenesis, male-killing, and host feminization. In this study, we used three sets of Wolbachia-specific primers (16S rDNA, ftsZ, and wsp) in conjunction with the polymerase chain reaction (PCR), cloning and sequencing to study the infection of fruit flies (Anastrepha spp. and Ceratitis capitata) by Wolbachia. The flies were collected at several localities in Brazil and at Guayaquil, Ecuador. All of the fruit flies studied were infected with Wolbachia supergroup A, in agreement with the high prevalence of this group in South America. Phylogenetic analysis showed that the wsp gene was the most sensitive gene for studying the relationships among Wolbachia strains. The Wolbachia sequences detected in these fruit flies were similar to those such as wMel reported for other fruit flies. These results show that the infection of Anastrepha fruit flies by Wolbachia is much more widespread than previously thought.     

Methoprene application and diet protein supplementation to male melon fly,Bactrocera cucurbitae,modifies female remating behavior

Methoprene (an analogue of juvenile hormone) application and feeding on a protein diet is known to enhance male melon fly, Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), mating success. In this study, we investigated the effect of these treatments on male B. cucurbitae's ability to inhibit female remating. While 14‐d‐old females were fed on protein diet, 6‐d‐old males were exposed to one of the following treatments: (i) topical application of methoprene and fed on a protein diet; (ii) no methoprene but fed on a protein diet; (iii) methoprene and sugar‐fed only; and (iv) sugar‐fed, 14‐d‐old males acted as controls. Treatments had no effect on a male's ability to depress the female remating receptivity in comparison to the control. Females mated with protein‐deprived males showed higher remating receptivity than females first mated with protein‐fed males. Methoprene and protein diet interaction had a positive effect on male mating success during the first and second mating of females. Significantly more females first mated with sugar‐fed males remated with protein‐fed males and females first mated with methoprene treated and protein‐fed males were more likely to remate with similarly treated males. Females mating latency (time to start mating) was significantly shorter with protein‐fed males, and mating duration was significantly longer with protein‐fed males compared with protein‐deprived males. These results are discussed in the context of methoprene and/or dietary protein as prerelease treatment of sterile males in area‐wide control of melon fly integrating the sterile insect technique (SIT).     

Methoprene application and diet protein supplementation to male melon fly,Bactrocera cucurbitae,modifies female remating behavior

Methoprene （an analogue of juvenile hormone） application and feeding on a protein diet is known to enhance male melon fly, Bactrocera cucurbitae Coquillett （Diptera： Tephritidae）, mating success. In this study, we investigated the effect of these treatments on male B. cucurbitae＇s ability to inhibit female remating. While 14-d-old females were fed on protein diet, 6-d-old males were exposed to one of the following treatments： （i） topical application of methoprene and fed on a protein diet; （ii） no methoprene but fed on a protein diet; （iii） methoprene and sugar-fed only; and （iv） sugar-fed, 14-d-old males acted as controls. Treatments had no effect on a male＇s ability to depress the female remating receptivity in comparison to the control. Females mated with protein-deprived males showed higher remating receptivity than females first mated with protein-fed males. Methoprene and protein diet interaction had a positive effect on male mating success during the first and second mating of females. Significantly more females first mated with sugar-fed males remated with protein-fed males and females first mated with methoprene treated and protein-fed males were more likely to remate with similarly treated males. Females mating latency （time to start mating） was significantly shorter with protein-fed males, and mating duration was significantly longer with protein-fed males compared with protein-deprived males. These results are discussed in the context of methoprene and/or dietary protein as prerelease treatment of sterile males in area-wide control of melon fly integrating the sterile insect technique （SIT）.     

New mariner elements in Anastrepha species (Diptera: Tephritidae)

Mariner-like elements (MLE) are members from class II of transposable elements also known as DNA transposons. These elements have a wide distribution among different groups of organisms, including insects, which can be explained by horizontal and vertical gene-transfer. MLE families have been described in tephritid flies and other genera. During screening for Wolbachia bacteria in fruit flies of the genus Anastrepha, we discovered two sequences related to mariner-like elements. Based on these sequences, we designed primers that allowed us to isolate and characterize two new mariner-like elements (Anmar1 and Anmar2) in Anastrepha flies. These elements, which belong to the mellifera and rosa subfamilies have a low nucleotide diversity, and are probably inactive and acquired by vertical transfer. This is the first report of mariner-like transposons in flies found in South America.     

Anastrepha ludens and Anastrepha serpentina (Diptera: Tephritidae) do not infest Psidium guajava (Myrtaceae), but Anastrepha obliqua occasionally shares this resource with Anastrepha striata in nature

This study examined whether economically important fruit fly species Anastrepha ludens (Loew), Anastrepha serpentina (Wiedemann), and Anastrepha obliqua (Macquart) (Diptera: Tephritidae) may opportunistically exploit guavas, Psidium guajava L. (Myrtaceae), growing near preferred natural hosts. We collected 3,459 kg of guavas and 895 kg of other known host species [sour orange, Citrus aurantium L.; grapefruit, Citrus paradisi Macfadyen; mango, Mangifera indica L.; white sapote, Casimiroa edulis La Llave and Lex.; sapote, Pouteria sapota (Jacq.); sapodilla, Manilkara zapota L.; and wild plum, Spondias purpurea L. and Spondias mombin L.] along an altitudinal gradient over a 4-yr period (2006-2009). Plants were growing in sympatry in 23 localities where the guavas are usually infested in the state of Veracruz, M6xico. The guava samples yielded 20,341 Anastrepha spp. pupae in total (overall mean, 5.88 pupae per kg of fruit). Confirming previous reports, Anastrepha fraterculus (Wiedemann) and Anastrepha striata (Schiner) were found heavily infesting guavas in Veracruz. Importantly, although we did not find evidence that A. ludens and A. serpentina are able to attack this valuable commodity, we document for the first time in the agriculturally important state of Veracruz that P. guajava is an alternative natural host plant of A. obliqua. We recovered two fruit in the mango-growing locality of la Vibora, Tlalixcoyan, that harbored larvae of A. striata and A. obliqua. This finding has important practical implications for management of A. obliqua. Over the entire altitudinal gradient, when individual fruit infestation was examined, a dynamic pattern of species dominance was unveiled with guavas growing below 800 m above sea level mainly attacked by A. striata and a progressive replacement with increasing altitude by A. fraterculus. Interestingly, most individual fruit examined (97%) harbored a single species of fruit fly, a finding that may be taken as evidence of competitive displacement among sympatric species of fruit flies. Based on this study and previously published work by us on this topic, we conclude that literature reports indicating that A. ludens and A. serpentina infest guavas under field conditions should be questioned.     

Pheromone deposition on leaf territories by male Caribbean fruit flies,Anastrepha suspensa (loew) (Diptera: Tephritidae)

Male Caribbean fruit flies apply everted anal membranes associated with pheromone glands to the substrate while on leaf territories. There is a peak in abdominal dipping at the onset of the photoperiod, followed by a decline and then a more extensive period of activity in the second half of the photoperiod. During peak signaling periods, most males had a distinct set of lateral abdominal phermone glands protruded for most of the time. However, the frequency of anal pheromone gland dipping varied considerably over time. Episodes of wing fanning (which may disperse pheromones) and abdomen dipping coincide during a male's tenure on a host leaf. Host-plant leaves were contained for 48 h with signaling males or immature females or kept without insects. Several, though not all, of the constituents of the pheromone were found on leaves within 1 h of removing signaling males. None of these compounds occurred on either type of control leaf. Mature virgin female flies were more likely to be found in contact with host leaves that had been previously exposed for 48 h to the activities of sexually mature males than with unexposed control leaves. There was no difference in the reaction of mature virgin female flies to unexposed control leaves or leaves previously exposed to the activities of other sexually immature female or male flies for 48 h. Presumably, the deposition of pheromones by mature males accounts for the difference in reactions.     

Alcohol dehydrogenase activities and ethanol tolerance in Anastrepha (Diptera, Tephritidae) fruit-fly species and their hybrids

The ADH (alcohol dehydrogenase) system is one of the earliest known models of molecular evolution, and is still the most studied in Drosophila. Herein, we studied this model in the genus Anastrepha (Diptera, Tephritidae). Due to the remarkable advantages it presents, it is possible to cross species with different Adh genotypes and with different phenotype traits related to ethanol tolerance. The two species studied here each have a different number of Adh gene copies, whereby crosses generate polymorphisms in gene number and in composition of the genetic background. We measured certain traits related to ethanol metabolism and tolerance. ADH specific enzyme activity presented gene by environment interactions, and the larval protein content showed an additive pattern of inheritance, whilst ADH enzyme activity per larva presented a complex behavior that may be explained by epistatic effects. Regression models suggest that there are heritable factors acting on ethanol tolerance, which may be related to enzymatic activity of the ADHs and to larval mass, although a pronounced environmental effect on ethanol tolerance was also observed. By using these data, we speculated on the mechanisms of ethanol tolerance and its inheritance as well as of associated traits.     

Reproductive behaviour of the South American fruit fly Anastrepha fraterculus (Diptera: Tephritidae): laboratory and field studies

Abstract. The mate choice, courtship and oviposition behaviour of laboratory-reared and field-collected Anastrepha fraterculus (Wied.) were compared. In laboratory cultures in Southampton the duration of male calling activity in small leks increased gradually from 1-2h at 5 days old to up to 7 h at 10 days. This finding correlates with previous reports on the time at which male salivary glands, which are believed to produce sex pheromone, are fully developed. Wild flies which emerged from infested fruits in Brazil began to oviposit on the day they mated, whereas in laboratory flies oviposition began 1 day following the first mating. Both types of fly usually defended their position on a particular fruit throughout the day, and re-mated with either virgin or mated males. There was no significant difference in mating duration. Females did not copulate before the mean age (±SE) of 16.8±0.9 days. For both types of flies mating initiation occurred in the first 2h of photophase, with virgin females choosing mainly mated males. The average number of matings in the laboratory was three for females and four for males, and the interval between matings in females was significantly increased after the second mating. It is suggested that the tendency of virgin females to mate with mated males will lead to increased fitness, as males are on average 48 days old at their second mating. The potential life span of around 200 days for both sexes would allow adults to bridge the gap between seasonally available fruits in warm-temperate and sub-tropical South America.     

Evidence for an oviposition-deterring pheromone in Tephritis bardanae (Schrank) (Diptera: Tephritidae)

Summary Female Tephritis bardanae (Schrank) exhibit a characteristic ovipositor-dragging behaviour immediately after laying eggs into a flowerbud of Arctium minus (Hill) Bernh. To establish whether this behaviour is associated with an oviposition-deterring pheromone (ODP), female T. bardanae were presented with clean, unattacked flowerbuds and fly activity was monitored using video recording equipment. The distribution of oviposition and fly behaviour were analysed. Avoidance of attacked buds was revealed by the oviposition pattern becoming overdispersed. Spacing out of eggs continued until, on average, each bud contained one egg-batch, after which the distribution became more random or clumped. Analysis of fly behaviour showed that attacked and unattacked buds received similar numbers of visits, but fewer oviposition attempts were made on attacked buds. This behaviour was consistent with use of a contact pheromone deterring repeated oviposition and applied to the bud surface during ovipositor-dragging. Avoidance of attacked buds should increase the efficiency of resource use by T. bardanae populations in the field; however, distributions of egg-batches in flowerhead samples collected from Monks Wood NNR, Cambridgeshire, during 1983–1985, were highly clumped and did not provide supportive evidence. This suggests that the effectiveness of oviposition deterrence in the field is reduced, because the active life of ODP under natural conditions is short, and/or because wild females frequently experience high oviposition drive due to scarcity of suitable flowerbuds.