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Understanding the dynamics of larval habitat utilization by mosquito communities is crucial for the design of efficient environmental control strategies. The authors investigated the structure of mosquito communities found at hotel compounds in Zanzibar, networks of mosquito interactions with larval habitats and robustness of mosquito communities to elimination of larval habitats. A total of 23 698 mosquitoes comprising 26 species in six genera were found. Aedes aegypti (n = 16 207), Aedes bromeliae/Aedes lillie (n = 1340), Culex quinquefasciatus (n = 1300) and Eretmapodites quinquevitattus (n = 659) were the most dominant species. Ecological network analyses revealed the presence of dominant, larval habitat generalist species (e.g., A. aegypti), exploiting virtually all types of water holding containers and few larval habitat specialist species (e.g., Aedes natalensis, Orthopodomyia spp). Simulations of mosquito community robustness to systematic elimination of larval habitats indicate that mosquito populations are highly sensitive to elimination of larval habitats sustaining higher mosquito species diversity. This study provides insights on potential foci of future mosquito-borne arboviral disease outbreaks in Zanzibar and underscores the need for detailed knowledge on the ecological function of larval habitats for effective mosquito control by larval sources management.

Citrus Research International; Hortgro Science; South African Table Grape Industry and National Research Foundation.

The trade-off between lifespan and reproduction is central to our understanding of life-history evolution. Laboratory selection experiments have been a powerful tool for quantifying this trade-off, but these tend to be restricted in taxonomic scope, which may limit our understanding. In addition, research often focuses on the trade-off between lifespan and reproductive effort in females, and far less data test how lifespan trades off with different aspects of male reproduction (e.g. pre- and post-copulatory reproductive investment). Here, we examined the trade-off between lifespan and reproduction in females and males of the marula fruit fly, Ceratitis cosyra (Walker) (Diptera: Tephritidae). To do so, we selected downward or upward on age of peak female egg laying in C. cosyra for twenty generations. In multiple generations, we measured female and male lifespan and body size, female daily and lifetime fecundity, male courtship and mating success, as well as the number of sperm transferred at different ages and sperm storage asymmetry in spermathecae. Our selection regime appeared to achieve its aim; egg laying peaked earlier in females from downward selected lines than upward selected lines. The number of sperm transferred by males decreased in the upward selected flies, but other male reproductive traits remained the same across selection regimes. In contrast, with the wider literature, upward selection did not extend the lifespan of females or males after ten generations of selection. While lifespan in both sexes responded to selection on female egg laying schedules, it did not do so in a straightforward way. Moreover, male investment in reproductive traits was largely independent of selection regime. These counter-intuitive findings highlight the importance of working with a broad range of species and of considering the trade-off between reproduction and lifespan in both sexes. The trade-off between lifespan and reproduction has been extensively studied in model species using various types of laboratory selection. A limited number of species have been considered using this approach, and the majority of the studies have focused on female, rather than male, reproductive effort. Here, we selected downwards and upwards on age of female reproduction in the marula fruit fly and measured survival, female fecundity, reproductive schedule, as well as male sperm transfer, sperm storage asymmetry, mating and calling success. We found a moderate trade-off between lifespan and early fecundity in downward selected flies, whereas no obvious trade-off was observed in upward selected lines. Regardless of the selection regime, reproductive scheduling was affected in females but not in males, while lifespan was affected in both sexes. Our results show that the timing of reproduction can evolve independently across the sexes, highlighting the importance of studying both females and males.

Oviposition site selection by gravid female insects is an important determinant in species distribution, abundance, and population dynamics. Females may assess the suitability of a potential oviposition substrate by using cues from conspecific or heterospecific individuals already present. Here, we assessed whether the presence of conspecific or heterospecific larvae and parasites influenced oviposition decisions by the stable fly, Stomoxys calcitrans (Linneaus). Using dual and multiple-choice oviposition bioassays, we found that gravid female S. calcitrans avoided substrates with conspecific larvae, the larvae of house flies, Musca domestica (Linneaus), and the mite Macrocheles muscaedomesticae (Scopoli). Avoidance of conspecific and heterospecific larvae persisted in the dark, suggesting that this behaviour is mediated by chemical rather than visual cues. When we reared S. calcitrans in the presence of conspecific larvae and the larvae of house flies at different densities we found that this negatively affected emergence time, larval weight, larval survival, pupal weight, pupal survival, and adult weight. We also demonstrated that individuals of S. calcitrans developed in the presence of mites exhibited low egg hatchability, and poor larval and adult survival. Our study provides additional support for the “preference-performance” hypothesis in S. calcitrans, with gravid females preferring to lay eggs on a substrate that will enhance offspring fitness. We recommend that the chemical cues involved in avoidance by gravid female S. calcitrans of substrates with conspecific and heterospecific larvae should be elucidated. This could lead to the discovery of repellent chemicals important for S. calcitrans management.

Start-up funds were provided to CWW by the University of Pre-toria in the form of a Research Development Programme grant. Further research funding, as well as a Grant Holder-Linked Masters Scholarship to PDR, was also provided by the South African National Research Foundation through a Competitive Programme for Rated Researchers grant (Grant No: 93686) to CWW and CRA.

Markets importing citrus fruit including lemons, Citrus limon (L.) Burman f., from South Africa require that the fruit be free of fruit fly pests (Diptera: Tephritidae). Historically there has been no fruit fly infestation recorded on lemons destined for export from South Africa. In this study, we assessed the host status of commercial export grade Eureka lemons, Citrus limon (L.) Burmanf. cv. Eureka, for four fruit fly pest species of economic importance in South Africa: Ceratitis capitata (Wiedemann), Ceratitis rosa Karsch, Ceratitis quilicii De Meyer, Mwatawala & Virgilio, and Bactrocera dorsalis (Hendel). Trapping was conducted in 10 Eureka lemon orchards in two major citrus production regions over two citrus seasons between 2016 and 2017 to determine the level of fruit fly abundance in the sampled orchards. Lemons were collected at harvest over the two seasons in the same orchards where trapping was conducted. Fruit fly infestation of the sampled lemons was determined by dissection. Additionally, infestation of lemons was determined under forced exposure to mature mated females of C. capitata and B. dorsalis. Trapping data showed the presence of adults of all four fruit fly species in the sampled lemon orchards. No fruit fly infestation was detected in 43 222 Eureka lemons sampled at harvest. There was also no infestation of lemons under forced exposure conditions. The results of this study provide evidence with 99.99 % efficacy and a 99%confidence level that SouthAfrican commercial export grade Eureka lemon fruit is not a host for C. capitata, C. rosa, C. quilicii or B. dorsalis.

Daylight fluorescent pigment powders are frequently used to self-mark tephritid flies that are released in sterile insect technique programmes and for studies on their population ecology, movement and behaviour. This study was conducted to determine the effects of pigment colour and dose in marking the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). Six pigment colours (Astral Pink 1, Blaze 5, Stellar Green 8, Lunar Yellow 27, Comet Blue 60 and Invisible Blue 70) were applied to pupae at doses of 0, 2, 4, or 6 g/l. Under laboratory conditions, pigment colour had a small but significant effect on the number of partially emerged and deformed adults; the fewest of these were observed when flies were marked with Astral Pink 1. Pigment concentration, on the other hand, had no effect on adult emergence, partial emergence, deformed adults and mortality on the last day of eclosion. There was no significant effect of pigment colour on adult survival under laboratory and semi-field conditions. Under laboratory conditions, however, there was an effect of pigment concentration on adult survival depending on pigment colour. Visibility under an ultraviolet light and persistence of marks was significantly affected by pigment colour and concentration when observed under laboratory conditions, but not under semi-field conditions. Regardless of colour or dose, pigments used in the study were visible for at least 14 days, but began to fade by 21 days after adult eclosion. To mark B. dorsalis under temperate, warmsummer African conditions, all pigment colours tested in this study may be applied at 2–4 g/l pupae. Recaptures of marked and released flies may be underestimated as the flies age.

Adult holometabolous insects may derive metabolic resources from either larval or adult feeding, but little is known of whether adult diets can compensate for deficiencies in the larval diet in terms of stress resistance. We investigated how stress resistance is affected and compensated for by diet across life stages in the marula fruit fly, Ceratitis cosyra (Walker) (Diptera: Tephritidae). Larvae were fed diets containing either 8% torula yeast, the standard diet used to rear this species, or 1% yeast (low protein content similar to known host fruit). At emergence, adults from each larval diet were tested for initial mass, water content, body composition, and desiccation and starvation resistance or they were allocated to one of two adult diet treatments: sucrose only, or sucrose and yeast hydrolysate. The same assays were then repeated after 10 days of adult feeding. Development on a low protein larval diet led to lower body mass and improved desiccation and starvation resistance in newly emerged adults, even though adults from the high protein larval diet had the highest water content. Adult feeding decreased desiccation or starvation resistance, regardless of the diet provided. Irrespective of larval diet history, newly emerged, unfed adults had significantly higher dehydration tolerance than those that were fed. Lipid reserves played a role in starvation resistance. There was no evidence for metabolic water from stored nutrients extending desiccation resistance. Our findings show the possibility of a nutrient-poor larval environment leading to correlated improvement in adult performance, at least in the short term.

The five-spotted fruit fly, Ceratitis quinaria (Bezzi) (Diptera: Tephritidae), is distributed in parts of eastern and western Africa, northern Africa and southern Africa (including South Africa). The species also occurs outside of Africa, in Yemen. The host range of C. quinaria is narrow, with Mangifera indica L. being the main host of commercial importance. Ceratitis quinaria was claimed to be associated with citrus in Sudan although this claim was never substantiated and there has never been any confirmed reared record of C. quinaria on citrus despite numerous surveys of citrus across Africa. In order to verify the type of association that C. quinaria has with citrus, field surveys were carried out in South Africa to determine the distribution and seasonal occurrence of C. quinaria in commercial citrus orchards and the possible natural infestation of citrus by this species. Surveys on distribution of C. quinaria across South Africa were carried out in 1999 and 2000 by trapping with Ceratitislure (containing protein hydrolysate and β-caryophyllene). The seasonal occurrence of C. quinaria in the northern areas of South Africa was determined over two years between 2015 and 2017 by trapping with Enriched Ginger Oil (EGO), a male lure containing α-copaene. In the same trapping period, citrus and other fruit were sampled to determine infestation by C. quinaria. Additionally between 2009 and 2018, citrus fruit was sampled from the trees and ground in other commercial and non-commercial areas in the north of South Africa. All fruit samples collected were incubated for at least five weeks to allow rearing of flies to the pupal and adult stages. Trapping surveys conducted between 1999 and 2000 showed the presence of C. quinaria only in the northern areas of South Africa. Catches of C. quinaria males in EGO-baited traps were low in commercial citrus orchards (peak of catches being lower than 0.05 flies/trap/day). Catches of C. quinaria were mainly recorded outside of the citrus ripening period. No C. quinaria was reared from any of the citrus fruit sampled, even in those areas where the presence of the species was demonstrated by catches in EGO-baited traps. The fruit surveys therefore demonstrated the absence of natural infestation of citrus with C. quinaria in South Africa and supported existing biological information that citrus is not a host for C. quinaria.

Post-teneral dietary supplements have been found to improve mating performance of male Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (Q-fly) and show considerable promise for enhancement of sterile insect technique (SIT) programmes even when applied within the current 48 h pre-release holding period. However, Q-flies are released as a bisexual strain, and the positive effects of a diet including yeast hydrolysate for males may also boost reproductive development and sexual performance of females. Increased prevalence of mature sterile females can substantially dilute SIT efficacy as mating capacity of sterile males is largely depleted by sterile females rather than the relatively rare wild females. Here, we demonstrate that providing yeast hydrolysate for 48 h after adult emergence, emulating the current pre-release holding period of Q-fly SIT, leads to a significant increase in reproductive development and sexual performance in male Q-flies. In contrast, female Q-flies with access to yeast hydrolysate for 48 h had ovaries that were poorly developed and, particularly at younger ages, were less likely to mate and remate than females with continuous, ad libitum access to yeast hydrolysate. Our findings suggest that addition of yeast hydrolysate into the pre-release diet of Q-flies could be a cost-effective means of releasing a bisexual strain with competitive males but with sexually immature females, thereby rendering it operationally more similar to a unisexual strain.

Diet has a profound influence on the fitness of adult tephritid flies. Mass-reared flies are provided yeast hydrolysate as a rich source of nutrition that supports rapid sexual development and mating success. In contrast, wild tephritid flies often live in environments where food may be hard to find, and these are the conditions that sexually immature mass-reared sterile males encounter when released into the field during sterile insect technique campaigns. The effect of natural food sources (bat guano, bird droppings, citrus pollen, and wheat pollen) on the sexual development of adult mass-reared fertile, mass-reared sterile, and wild male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), was determined by measuring ejaculatory apodeme size. Inclusion of yeast hydrolysate in the adult diet was associated with faster growth of the ejaculatory apodeme in comparison with all other diets. Effects of diet were far less pronounced in mass-reared males, which may indicate reduced nutritional requirements, whereas the ejaculatory apodeme of wild males fed on natural sources of food or sucrose alone did not increase in size over the first 20 days of adult life.

Desiccation resistance is important for the survival of adult insects, although this key physiological trait has rarely been studied in tephritid flies. In the present study, desiccation resistance of female and male adult Queensland fruit flies Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) is determined with respect to age after adult eclosion. Resistance to acute starvation is measured over the same period to disentangle the competing roles of water loss and food deprivation. Survival of adult B. tryoni subjected to conditions of low humidity and starvation is reduced considerably compared with adults that are subjected to starvation alone. Desiccation resistance of adult female B. tryoni is generally lower than that of adult males. Desiccation resistance of adult B. tryoni declines in a continuous and regular manner over the first 20 days after adult eclosion. The regular pattern of declining resistance to desiccation with age in B. tryoni indicates that this reduction is not associated with the onset of maturity and maintenance of reproductive structures, nor with sexual activity. By contrast, resistance to starvation is similar at 0 and 6 days after adult eclosion, and declines thereafter. Survival under starvation and water stress is not related to wing length, which is a standard measure of fly size.

Mass-reared sterile tephritid flies released in sterile insect technique (SIT) programmes exhibit behaviour, physiology and longevity that often differ from their wild counterparts. In the present study, video recordings of flies in laboratory cages are used to determine whether the sequential processes of mass-rearing and sterilization (using gamma radiation) that are integral to SIT affect general activity patterns of male and female Queensland fruit flies Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (‘Q-flies'). Compared with wild flies, mass-reared flies exhibit a marked reduction in overall activity, and further reduction is found after sterilization. In terms of the frequency of activities, both fertile and sterile mass-reared Q-flies fly less often and exhibit more bouts of inactivity and grooming than wild Q-flies. In addition, in terms of the duration of activities, fertile and sterile mass-reared Q-flies spend less time flying and more time walking, grooming and being inactive than wild Q-flies. Although fertile and sterile mass-reared flies are similar in other regards, sterile mass-reared flies spend more time being inactive than fertile mass-reared flies. These findings raise new questions about how changes in behaviour and activity levels may influence the performance of mass-reared sterile Q-flies in the field, as well as the physiological and metabolic processes that are involved. The frequency and duration of inactivity could provide a simple but powerful and biologically relevant test for quality in mass-rearing and SIT programs.

Male insects that are unable to replenish sperm supplies between matings can suffer fitness costs either because their mates are more likely to accept subsequent suitors, or because their sperm are outnumbered when females do remate. We assessed the ability of fertile and sterile (irradiated) male Queensland fruit flies, Bactrocera tryoni (‘Q-flies’), to have sperm stored by five sequential mates as well as the association between sperm depletion and female remating tendency. Sequential mates of fertile males stored similar numbers of sperm, indicating ample ability to replenish and maintain constant supplies between their once-daily mating opportunities. In contrast, sequential mates of sterile males stored progressively fewer sperm, with only trivial numbers of sperm stored by females mated by sterile males that had mated with two or more females previously. Despite the massive reduction in sperm storage by sequential mates of sterile males, fertile and sterile males were similar in their ability to induce sexual inhibition in their mates (to at least 30 days) and neither showed any decline in this ability across sequential matings. The ability of multiple-mated sterile males to induce sexual inhibition in their mates despite near or complete absence of sperm provides compelling evidence that sperm abundance plays no role in the induction of sexual inhibition in this species.

Recent laboratory studies of mass-reared flies in small cages have found that periods of just 24- or 48-h access to yeast hydrolysate can substantially enhance mating performance of mass-reared male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) ('Q-flies'). Using field cage tests that provide a better approximation of nature, we here investigated whether access to yeast hydrolysate for 48 h after adult emergence improves the ability of male and female mass-reared, sterile Q-flies to compete sexually with wild-type flies that had been provided continuous access to yeast hydrolysate. Mating probability of sterile males was significantly increased by 48-h access to yeast hydrolysate; sterile males provided 48-h access to yeast hydrolysate had mating probability similar to that of wild males provided continuous access to yeast hydrolysate, whereas sterile males deprived of access to yeast hydrolysate had much lower mating probability. Unlike males, access to yeast hydrolysate for 48 h did not increase mating probability of sterile female Q-flies. We instead found that wild females provided continuous access to yeast hydrolysate had higher mating probability than sterile females that did or did not have 48-h access to yeast hydrolysate. This result raises the possibility that a bisexual Q-fly strain might operate essentially as a male-only release when the flies are given access to yeast hydrolysate during a 48-h pre-release holding period. Sterile males given access to yeast hydrolysate for 48 h mated significantly earlier in the evening than wild males and, as in other recent studies, this tendency was associated with an increased tendency to mate on the trees rather than the cage walls. There was no evidence of sexual isolation in this study, as wild and sterile mass-reared flies showed no evidence of preferential mating with their own kind. Further studies are now needed to assess the potential for pre-release access to yeast hydrolysate to improve sexual performance and longevity of sterile, mass-reared, Q-flies in the field.

Feeding on yeast hydrolysate (a source of nitrogen) has a strong influence on the physiology and behaviour of the Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), affecting longevity, sexual maturation, oogenesis, and mating performance. In this study, we demonstrate that access to yeast hydrolysate also influences the development of attraction to cue-lure in Q-flies. We provided virgin Q-flies various periods of access to yeast hydrolysate (continuous, 48 h, 24 h, or deprived). Attraction of males to cue-lure was increased and occurred at an earlier age when they were fed yeast hydrolysate. Males given continuous access were strongly attracted to cue-lure at a younger age (8 days after emergence), but by 12 days after emergence attraction of males given access to yeast hydrolysate for 48 h did not differ from males given continuous access. Attraction by males deprived or given just 24 h access to yeast hydrolysate was always significantly lower than those of males with continuous access. Male attraction to cue-lure was highest in the early morning. While cue-lure is most often thought of as a male attractant, virgin female Q-flies were caught in cue-lure traps at dusk at ages when they are known to be sexually mature. We suggest that cue-lure or similar natural chemicals play a role in the Q-fly mating system. γ-Irradiation used to induce sterility had no significant effect on attraction to cue-lure by Q-flies.

The mating performance field cage test is a required periodic quality-control assessment for factory-reared fruit flies used for the sterile insect technique. The FAO/IAEA/USDA guidelines for assessing fly quality state that if during tests a large proportion of flies call and mate on cage walls, away from host trees, then environmental conditions within the cage need to be adjusted and tests repeated. Here we test effects of cage design, specifically mesh colour (green, white) and addition of supplementary shade, on the mating behaviour of Queensland fruit fly (Q-fly), Bactrocera tryoni Froggatt (Diptera: Tephritidae). Observations were made over a 4-h period at dusk when these flies mate. Changes in environmental conditions in each cage over the dusk period varied with cage design. We recorded the highest proportion of matings taking place on trees as opposed to cage walls (>90%) in the unshaded white cage, the shaded white and un-shaded green cages being intermediate (ca. 70%), and the shaded green cage had the least (ca. 40%). The effects of field cage colour and supplementary shade on mating behaviour are discussed. We recommend that Q-fly field cage tests should be conducted in cages with a light coloured mesh, and that supplementary shading should only be applied if there is a need to adjust temperature and light within the cage.

Dispersal of immature male and female Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), was assessed over a period of 1 week from a single release point on three separate occasions using an array of Lynfield traps baited with cue-lure and odouriferous yellow or black sticky spheres baited with food lure (protein autolysate). Lynfield traps recaptured males; yellow or black spheres recaptured both sexes in approximately equal proportions, although at a much lower rate. As a percentage of the recapture rate for males by Lynfield traps, the mean recapture rate for yellow spheres ranged from 1.0% to 7.5% for males and 0.7% to 4.0% for females, whereas the recapture rates for black spheres ranged from 0.4% to 3.6% and 0.6% to 1.8%, respectively. The rate of recapture of sterile male flies was greater than that of unsterilised flies; this may have been due to a faster maturation rate in sterile males or because a greater proportion of them remained within the trap array rather than dispersing. There was no significant trend in recapture rate with distance from the release point to the edge of the array (88 m), except in the case of females on sticky traps where no trend was detected between 19 and 88 m. These results lend support to assumptions made about the distribution of males and females with respect to the minimum breeding density of fruit fly propagules invading a fly-free zone, and the method chosen to distribute sterile B. tryoni for the sterile insect technique.

The importance of male aggregation size for female visitation and initiation of male pheromone-calling was investigated in Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) using artificial male aggregations in large laboratory cages. Female B. tryoni visited the largest aggregation more frequently than single males in association with a higher proportion of calling males, but there was no correlation between aggregation size and female visitation. Female B. tryoni had a limited capacity to perceive a difference between the number of calling males. Calling propensity of male B. tryoni was increased by the presence of conspecific males. Increased calling propensity in larger groups of male B. tryoni may be due to social facilitation of male calling behaviour. Female visitation at aggregations was only weakly associated with male calling, suggesting that aggregation size and the number of pheromone-calling males are not the only factors important in locating mates in B. tryoni, and it is possible that low-density populations could persist so long as females can encounter single males.

Background The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is a highly invasive species now with an almost cosmopolitan distribution. Two other damaging, polyphagous and closely-related species, the marula fruit fly, Ceratitis cosyra (Walker), and the Natal fly, Ceratitis rosa Karsch, are not established outside of sub-Saharan Africa. In this study, adult water balance traits and nutritional body composition were measured in all three species at different temperatures and levels of relative humidity to determine whether tolerance of water stress may partially explain their distribution. Results Adult C. capitata exhibited higher desiccation resistance than C. rosa but not C. cosyra. Desiccation resistance of C. capitata was associated with lower rates of water loss under hot and dry conditions, higher dehydration tolerance, and higher lipid reserves that were catabolised during water stress. In comparison with C. capitata, C. cosyra and C. rosa lost water at significantly higher rates under hot, dry conditions, and did not catabolise lipids or other sources of metabolic water during water stress. Conclusions These results suggest that adult physiological traits permitting higher tolerance of water stress play a role in the success of C. capitata, particularly relative to C. rosa. The distribution of C. cosyra is likely determined by the interaction of temperature with water stress, as well as the availability of suitable hosts for larval development. Electronic supplementary material The online version of this article (doi:10.1186/s12983-016-0147-z) contains supplementary material, which is available to authorized users.

Macroinvertebrate assemblages can vary with season as a result of changing environmental conditions and phenology of individual species. The objective of this study was to determine whether results from the South African Scoring System version 5 (SASS5) are affected by season. The standard SASS5 protocol was used to sample three sites on the Skeerpoort River, South Africa, in autumn, winter and spring 2013, and summer 2014. At each site, stream morphology was characterised and physico-chemical variables were measured. Two-way analysis of variance (ANOVA) was used to compare SASS indices in relation to site and season, and a one-way ANOVA was used to test the effect of season using both current and historical data. Macroinvertebrate assemblage similarity of sites was determined using non-metric multidimensional scaling ordination, followed by analysis of similarity. Whilst macroinvertebrate assemblages differed between seasons and sites, there was no seasonal variation in the values of SASS indices, but they did differ between sites. SASS5 appears to be robust to seasonal variation in macroinvertebrate assemblage and seems suitable for use throughout the year in a perennial river draining the South African highveld region. Keywords: aquatic macroinvertebrates, bioassessment, seasonal variation, water quality African Journal of Aquatic Science 2014, 39(4): 369–376

The effects of domestication and irradiation on the mating behaviour of males of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) were investigated by caging wild, laboratory-domesticated and sterile (laboratory-domesticated, gamma-irradiated) males with wild females. Mating behaviour of mass-reared males was different from that of wild males, although behaviour of wild and sterile males was similar. Mass-reared males engaged in mounting of other males much more frequently than wild and sterile males, and began calling significantly earlier before darkness. Unnatural selection pressures imposed in mass-rearing conditions may explain these changes in mass-reared male behaviour. Male calling did not appear to be associated with female choice of mating partners, although this does not exclude the possibility that calling is a cue used by females to discriminate among mating partners. Despite differences in behaviour, frequency of successful copulations and mating success were similar among wild, mass-reared and sterile males.