Performance and feeding behavior of Ceratitis capitata: comparison of a wild population and a laboratory population

Experiments were carried out to test the performance and some aspects of feeding behavior in two populations of Ceratitis capitata (a population reared in the laboratory for 16 years, i.e., approximately 160 generations, and a wild one obtained from infested coffee, Coffea arabica grains). Two types of food were used in the experiment: an artificial yeast diet used for laboratory rearing and papaya (Carica papaya), a natural host of the fly. The performance parameters tested were percent emergence, time to emergence, adult female size, and egg production during the pre-oviposition phase (first five days of adult life). The behavioral aspects tested were food preference by newly hatched larvae, induction, estimated ingestion of the two diets, whether the larvae placed on one diet stayed there or moved to the other diet, and acceptance of food for oviposition. The results indicated that the performance of the wild population was superior when the flies fed on papaya, whereas the performance of the laboratory population was similar with the two diets; the wild population showed a strong preference for papaya in all choice experiments, whereas the laboratory population showed no diet preference; the females of the wild population only oviposited on pieces of papaya that had not been peeled, and did not oviposit in the artificial diet; the females of the laboratory population oviposited indiscriminately on unpeeled and peeled papaya and on the artificial diet.     

Protein: carbohydrate ratios promoting sexual activity and longevity of male Queensland fruit flies

Nutrition is commonly a powerful determinant of sexual performance in insects, and recent studies have found this to be the case in Queensland fruit flies (Tephritidae: Bactrocera tryoni Froggatt; 'Q-flies'); male Q-flies allowed to self-regulate intake of yeast hydrolysate, a rich source of amino acids and vitamins used in most mass-rearing programmes (protein) and sucrose (carbohydrate), had greatly enhanced sexual performance compared with males provided only sucrose. While some yeast hydrolysate is clearly beneficial for the sexual performance of adult male Q-flies, the questions of what proportion of yeast hydrolysate in the diet is sufficient to yield full benefits, or is too much, have not yet been addressed. To address these questions, the present study assessed sexual performance and longevity of adult male Q-flies maintained on diets containing various proportions of yeast hydrolysate and sucrose. Male Q-flies maintained as adults on dry mixtures containing 9%, 17% or 25% yeast hydrolysate had mating probability, mating latency, copula duration and longevity similar to those provided yeast hydrolysate and sucrose in separate dishes and allowed to self-regulate intake. As in previous studies, while longevity was unaffected we found a marked reduction in sexual performance when the flies were completely denied access to yeast hydrolysate, and the few that did mate had relatively short copulations. At the other extreme, flies receiving diets with high levels of yeast hydrolysate (50%, 75%, 83% and 91%) suffered marked reductions both in longevity and in mating performance.     

Nutrient balance in medfly, Ceratitis capitata, larval diets affects the ability of the developing insect to incorporate lipid and protein reserves

The Mediterranean fruit fly [Ceratitis capitata Wiedemann (Diptera: Tephritidae)], or medfly, is mass produced in many facilities throughout the world to supply sterile flies for sterile insect technique programs. Production of sterile males requires large amounts of larval and adult diets. Larval diets comprise the largest economic burdens in the mass production of sterile flies, and are one of the main areas where production costs could be reduced without affecting quality and efficacy. The present study investigated the effect of manipulating diet constituents on larval development and performance. Medfly larvae were reared on diets differing in the proportions of brewer's yeast and sucrose. We studied the effect of such diets on the ability of pupating larvae to accumulate protein and lipids, and on other developmental indicators. Except for diets with a very low proportion of brewer's yeast (e.g., 4%), pupation and adult emergence rates were in general high and satisfactory. The ability of pupating larvae to accumulate lipid reserves and proteins was significantly affected by the sucrose and yeast in the diet, and by the proportion of protein to carbohydrates (P/C). In contrast to previous nutritional studies conducted with other insects, low P/C in medfly larval diets (with excess dietary carbohydrates) resulted in pupating medfly larvae having a relatively reduced load of lipids; medfly larvae protein contents in these diets were, as expected, relatively low. Similarly, high P/C ratios in the diet produced larvae with high protein and lipid contents. Differences with other insects may be due to differential post‐ingestion regulation where a high dietary carbohydrate diet reduces the lipogenic activity of the larvae, and induces a shift from lipid to glucose oxidation. Larvae reared on low P/C diets spent more time foraging in the diet than larvae maintained on a high P/C diet, suggesting a compensatory mechanism to complement nutrient intake. The results suggest that the content of brewer's yeast, the most expensive diet component, could be fine‐tuned without apparently affecting fly quality.     

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

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

Trends in lipid and protein contents during medfly aging: an harmonic path to death

Survival and egg-laying trends were investigated in Mediterranean fruit flies (Ceratitis capitata) adults maintained on a sucrose-only diet, or on a full diet that consisted of a 3:1 sucrose and yeast hydrolizate mixture. In addition, we followed the total individual lipid and protein contents of aging flies in a cohort. Survival trends and life expectancy parameters at eclosion for males and females on full diet and for males on sucrose only were very similar. In contrast, the mortality of females on sucrose only was high early in life, but then slowed down. Egg-laying was ten times greater in female flies on full diet than in flies on sucrose only. Lipid contents in males and females on both types of diets were very similar, and harmonically oscillated with an amplitude of approximately 10 days. Successive crests of lipids tended to be smaller with the ageing of the cohort, and lipids contents significantly dropped at very advanced ages and close to the maximal age of the whole cohort. Protein contents of flies maintained on a full diet were high and stayed at a constant level throughout the entire life of the cohort. Protein levels in males and females on sucrose only dropped drastically during the first days of adult life, but then stayed stable at a low level until advanced ages. We propose that the synchronous rhythmic oscillation in lipid contents of male and female flies seems to be independently set by an internal clock. Protein reserves are allocated according to the access to protein food sources and these levels of protein are closely associated to egg production and mortality. Our results are discussed in view of resource allocation during reproduction and senescence.     

Sexual development of wild and mass‐reared male Queensland fruit flies in response to natural food sources

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.     

Rearing of the pupal parasitoid Brachymeria intermedia on veal homogenate-based artificial diets: evaluation of factors affecting effectiveness

The pupal parasitoid Brachymeria intermedia (Nees) was reared from egg to fecund adult on various veal homogenate-based artificial diets. For every replicate 12.12 ml of each diet were used. Four diets were tested first. Two media, one devoid of and one supplemented with 1 ml Galleria mellonella pupal extract, contained 0.19 g wheat germ and 0.19 g yeast extract each. The other two, one added with and the other devoid of host extract, contained 0.38 g yeast extract each and no wheat germ. All diets also contained chicken egg yolk (1.1 and 0.8 ml in the diets without and with host extract, respectively). The amount of yeast extract was seen to have no significant effect on any of the developmental parameters considered. The replacement of wheat germ with yeast extract was therefore not convenient, considering that the former is far more economical than the latter. Pupal extract was instead found to have a significant effect on pupal and adult yields. The highest adult yield (= 53.2%) was obtained on the diet supplemented with 0.38 g yeast extract and containing host pupal extract. A further four media, each comprising a different kind of material derived from G. mellonella, were subsequently tested. Adult yields were such as to suggest the possibility of replacing pupal with larval extract in the diets as the latter is easier to prepare since there are no cocoons to be removed. In contrast, when the diets were supplemented with larval or pupal homogenate, adult yields dramatically dropped. When B. intermedia was reared in groups rather than individually, most larvae died before attaining maturity. Only two parasitoids, in two different replicates, emerged as adults.     

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

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

Nutritional balancing in fruit flies: performance of wild adult females of Anastrepha obliqua (Diptera: Tephritidae) fed on single-food or food-pair treatments

The aim of the present study was to investigate the effects of different artificial diets, in which sucrose and brewer's yeast were offered separately (food-pair treatment) or mixed (single-food treatment), on the regulation of nutrient ingestion and the performance of wild adult females of Anastrepha obliqua. The amount of diet consumed by females of A. obliqua increased as the concentration of yeast in the diet increased, revealing a phagostimulant effect of yeast. The amount of sucrose ingested was constant in all groups, showing that these flies regulate the ingestion of sucrose. Longevity and production of eggs/female were similar in both groups. Our results suggest that A. obliqua females regulate the ingestion of nutrients to obtain an adequate performance. Dietary self-selective behavior was more efficient for the females of A. obliqua than feeding on a single-food, because the self-selecting flies ingested less food and had a similar performance as the ones fed on the single-food treatment.     

Amino acids in nectar enhance longevity of female Culex quinquefasciatus mosquitoes

Culex mosquitoes feed on a wide range of nectars consisting of mostly carbohydrates and amino acids, however, little is known about the utilization and effects of these different carbohydrates and their accompanying amino acids on longevity. Culex quinquefasciatus larvae were reared on low- and high-quantity food diets to produce adults that were nutritionally representative of wild-caught and laboratory-reared mosquitoes. Emerging adults reared on low- or high-quantity food diets as larvae were then provided Lantana camara nectar mimics containing mixtures of carbohydrates and amino acids to evaluate effects of nectar amino acids on longevity. Carbohydrates (with or without amino acids) were a critical component of the adult diet, and in their absence, adult mosquitoes died within 3-5 days. The nectar mimic that contained both carbohydrates and amino acids did not increase adult longevity of males originating from either poorly or well-fed larvae. However, females receiving adult diets containing both carbohydrates and amino acids lived 5% longer than females fed adult diets with only sugar.     

Pre-release feeding on yeast hydrolysate enhances sexual competitiveness of sterile male Queensland fruit flies in field cages

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.     

Dietary glycerol and adult access to water: effects on fecundity and longevity in the almond moth

The quality of food eaten by larval insects will affect traits such as gamete production, fat reserves, muscle bulk and body size in the adult. Moreover, larvae also depend on high moisture content in the diet for survival. The almond moth (Ephestia cautella) (W.) (Lepidoptera; Pyralidae) does not feed as an adult although it continues to drink water. We tested the idea that an almond moth could compensate for a low-water diet as a larva by increasing its water intake as an adult. We reared larvae on two different food sources with different moisture regimes; standard laboratory diet with glycerol (relatively wet) and standard diet without glycerol (relatively dry). Half the adult moths from each treatment were given water to drink before their first and only mating. Our results show that wet larval diets (i.e. containing glycerol) significantly decreased fecundity (total number of eggs laid and the proportion of hatched larvae), whilst it significantly increased male and female longevity. The interaction effect of water access for adult males and females was significant, independent of the glycerol in the larval diet. Longevity in females that were not presented with water as adults was slightly higher if mated with a male that had had access to water, suggesting a mating donation of water. However, females that received water as adults showed a decreased longevity if mated with a male who had also had access to water as an adult, indicating a negative effect of water if received by both males and females. In addition, when the larval diet included glycerol, increased number of eggs laid decreased female longevity, whilst an absence of glycerol in the larval diet resulted in low female longevity that was unlinked with fecundity. Glycerol is used in many artificial insect diets and the fact that it shows a strong effect on key life-history traits (reproductive output and longevity in this species), merits careful re-examination of its effects on these important traits in other laboratory models. We also discuss the possibility that larval diet can affect female reproductive decisions.     

Development, long-term survival, and the maintenance of fertility in Neoseiulus californicus (Acari: Phytoseiidae) reared on an artificial diet

The effectiveness of non-prey food items, such as pollen, honeydew, and microbes, in maintaining phytoseiid mite populations is widely accepted. However, the availability of such naturally occurring non-prey foods varies with the season and surrounding environment; thus, it is difficult to manipulate and maintain supplies of these food sources. A great deal of research has examined the development and reproduction of phytoseiid mites on artificial diets. Although phytoseiid mites frequently develop, several studies have detected low fecundities of adult females reared on artificial diets. Therefore, the use of artificial diets for commercial propagation is often difficult. However, the potential of artificial diets to maintain phytoseiid mite populations has not yet been evaluated. In this study, we investigated the developmental success and survival of Neoseiulus californicus (McGregor) on an artificial diet. This mite may be one of the most effective phytoseiid species used in agricultural systems for the control of spider mites. N. californicus successfully developed on the artificial diets: 93.5-100% of individuals reached adulthood 4-7 days after hatching. The survival rates of gravid adult females maintained on the AD-1 artificial diet composed of yeast components, saccharides, and egg yolk at 25 degrees C were 100, 80, and 48.9% over 36, 60, and 90 days, respectively. Moreover, >80% of the surviving females maintained on AD-1 for 36 or 60 days laid eggs after being switched to a diet of the spider mite Tetranychus urticae Koch, although they had laid few eggs during the maintenance periods on the artificial diet. Our results indicate that artificial diets can serve as a potentially useful food source for the long-term maintenance of N. californicus populations.     

Nutrients, not caloric restriction, extend lifespan in Queensland fruit flies (Bactrocera tryoni)

Caloric restriction (CR) has been widely accepted as a mechanism explaining increased lifespan (LS) in organisms subjected to dietary restriction (DR), but recent studies investigating the role of nutrients have challenged the role of CR in extending longevity. Fuelling this debate is the difficulty in experimentally disentangling CR and nutrient effects due to compensatory feeding (CF) behaviour. We quantified CF by measuring the volume of solution imbibed and determined how calories and nutrients influenced LS and fecundity in unmated females of the Queensland fruit fly, Bactocera tryoni (Diptera: Tephritidae). We restricted flies to one of 28 diets varying in carbohydrate:protein (C:P) ratios and concentrations. On imbalanced diets, flies overcame dietary dilutions, consuming similar caloric intakes for most dilutions. The response surface for LS revealed that increasing C:P ratio while keeping calories constant extended LS, with the maximum LS along C:P ratio of 21:1. In general, LS was reduced as caloric intake decreased. Lifetime egg production was maximized at a C:P ratio of 3:1. When given a choice of separate sucrose and yeast solutions, each at one of five concentrations (yielding 25 choice treatments), flies regulated their nutrient intake to match C:P ratio of 3:1. Our results (i) demonstrate that CF can overcome dietary dilutions; (ii) reveal difficulties with methods presenting fixed amounts of liquid diet; (iii) illustrate the need to measure intake to account for CF in DR studies and (iv) highlight nutrients rather than CR as a dominant influence on LS.     

Rearing ofChaetorellia australis (Dipt., Tephritidae) on an artificial diet

Larvae of the tephritid flyChaetorellia australis Hering, which infests flowerheads of the yellow starthistleCentaurea solstitialis L. (Asteraceae), and which is a candidate species for biological control, of that weed, were reared for the first time and for two consecutive generations on an artificial diet. At a density of 0.5 eggs per g diet a yield of 18.5% F₁ adults (over hatched eggs), was obtained. When the density of eggs per g diet increased, the yield decreased. At 25°C the duration of development from egg to adult was 20–25 days for both generations. F₁ adults reared on artificial diet had an average longevity of 32.0 days for males and 34.9 days for females. The fecundity was 53.3 eggs per female and the egg hatchability 88.8%. These and other biological parameters are similar to those of wild flies.      

Behavioral, physical, and demographic changes in Drosophila populations through dietary restriction

Dietary restriction (DR) is a valuable experimental tool for studying the aging process. Primary advancement of research in this area has relied on rodent models, but attention has recently turned toward Drosophila melanogaster. However, little is known about the baseline effects of DR on wild-type Drosophila and continued experimentation requires such information. The findings described here survey the effects of DR on inbred, wild-type populations of Canton-S fruit flies and demonstrate a robust effect of diet on longevity. Over a circumscribed range of dietary conditions, healthy lifespan varies by as much as 121% for wild-type Drosophila females. Significant differences are also observed for male flies, but the magnitude of the DR effect is less robust. Mortality analyses of the survivorship data reveal that this variation in lifespan can be attributed to a modulation of the rate parameter for the mortality function - a change in the demographic rate of aging. Since the feeding of fruit flies is less easily controlled than that of rodents, this research also addresses the validity of applying a DR model to Drosophila populations. Feeding and body weight data for flies given the various dietary conditions surveyed indicate that Drosophila on higher-calorie diets consume a similar volume of food to those on a low-calorie diet, resulting in different levels of calorie intake. Fertility and activity levels demonstrate that the diets surveyed are comparable, and that increasing the calorie content of laboratory food up to twice the normal concentration is not pathologic for experimental fly populations.     

Additive and interactive effects of nutrient classes on longevity, reproduction, and diet consumption in the Queensland fruit fly (Bactrocera tryoni)

Insect lifespan is often closely linked to diet, and diet manipulations have been central to studies of ageing. Recent research has found that lifespan for some flies is maximised on a very low yeast diet, but once all yeast is removed, lifespan drops precipitously. Although effects of yeast availability on lifespan are commonly interpreted in terms of protein, yeast is a complex mix of nutrients and provides a rich source of vitamins, minerals and sterols. Elucidating which components of yeast are involved in this lifespan drop provides insights into more specific nutritional requirements and also provides a test for the commonplace interpretation of yeast in terms of protein. To this end, we fed Queensland fruit flies (Bactrocera tryoni) one of eight experimental diets that differed in the nutrient group(s) found in yeast that were added to sucrose: none, vitamins, minerals, amino acids, cholesterol, vitamin+mineral+cholesterol (VMC), vitamin+mineral+cholesterol+amino acids (VMCA), and yeast. We measured survival rates and egg production in single sex and mixed sex cages, as well as nutrient intake of individual flies. We found that the addition of minerals increased lifespan of both male and female flies housed in single sex cages by decreasing baseline mortality. The addition of just amino acids decreased lifespan in female flies; however, when combined with other nutrient groups found in yeast, amino acids increased lifespan by decreasing both baseline mortality and age-specific mortality. Flies on the yeast and VMCA diets were the only ones to show significant egg production. We conclude that the drop in lifespan observed when all yeast is removed is explained by missing micronutrients (vitamins, minerals and cholesterol) as well as the absence of protein in females, whereas minerals alone can explain the pattern for males. These results indicate a need for caution when interpreting effects of dietary yeast as effects of protein.     

Development of probiotic diets for the olive fly: evaluation of their effects on fly longevity and fecundity

One possible control strategy against the olive fly, Bactrocera oleae, the most serious olive crop pest, is the Sterile Insect Technique (SIT) application. However, a number of problems associated with this method remain that decrease the effectiveness of SIT, including the quality of reared insects. Taking the importance of the relationship between the olive fly and bacteria into consideration, the effects of probiotic diets enriched with Pseudomonas putida on B. oleae longevity and fecundity were evaluated. First, we found that the probiotic bacterium, P. putida, is conveyed from diets to the oesophageal bulb as well as to the fly midgut after feeding on the probiotic diet. Subsequently, B. oleae adults fed on either: (a) a standard full protein and sugar diet; (b) a sugar only diet; (c) a probiotic standard full protein and sugar diet; or (d) a probiotic sugar diet. Flies fed on probiotic diets were supplied with an inoculated gel containing P. putida; non‐inoculated gel was provided to the flies fed on non‐probiotic diets. B. oleae males and females that fed on sugar diets did not survive as long as those that fed on protein diets. A comparison of the longevity of adults fed on full diet and sugar with their respective probiotic diets revealed no significant difference. Males fed on the sugar only diet survived longer than males fed on probiotic sugar diet, and females fed on the full protein and sugar diet survived much longer than females fed on the full probiotic diet. As regarding fecundity, both full diets resulted in a higher number of eggs laid per female. Females fed on the probiotic sugar diet laid a higher number of eggs than females that fed on sugar only. The inoculated gel of the probiotic sugar diet contained a significantly higher quantity of leucine, isoleucine and proline than the non‐inoculated gel of the sugar only diet. The possible role of dietary bacteria in relation to functional aspects of olive fly physiology is discussed.     

Evaluation of yeasts in gel larval diet for Queensland fruit fly,Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (“Q‐fly”), is Australia’s most economically important insect pest of horticultural and commercial crops especially in the eastern regions. The sterile insect technique (SIT) has been adopted as an environmentally benign and sustainable approach for management of Q‐fly outbreaks. High‐performance larval diets are required to produce the millions of flies needed each week for SIT. Yeast products contribute amino acids (protein) to fruit fly larval diets, as well as carbohydrate, fat and micronutrients, but there can be substantial variation in the nutritional composition and suitability of yeast products for use in larval diets. Gel larval diets have recently been developed for large‐scale rearing of Q‐fly for SIT, and composition of these diets requires optimization for both performance and cost, including choice of yeast products. We assessed performance of Q‐flies reared on gel larval diets that contained debittered brewer’s yeast (Lallemand LBI2240), hydrolysed yeast (Lallemand FNILS65), inactivated brewer’s yeast (Lallemand LBI2250) and inactivated torula yeast (Lallemand 2160‐50), including blends. Q‐flies performed poorly when reared on diets containing only or mostly hydrolysed yeast in terms of pupal number, pupal weight and percentage of fliers. Performance was also poor on diets containing high proportions of torula yeast. Overall, debittered brewer’s yeast is recommended as the best option for Q‐fly gel larval diet, as it is cheap, readily available, and produces flies with good performance in quality control assays. Inactivated brewer’s yeast produced flies of comparable quality with only a modest increase in cost and would also serve as an effective alternative.     

Biology and life table studies of the oriental tobacco budworm,Helicoverpa assulta (Lepidoptera: Noctuidae), influenced by different larval diets

Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper (Capsicum frutescens L.), and tobacco (Nicotiana tobacum L.). We found that the average developmental time of immature stages was longest on tobacco (36.2 d), intermediate on pepper (34.4 d), and shortest on artificial diet (33.5 d). Immature survival from egg to pupa varied from 31% on tobacco, 43% on pepper, and 74% on artificial diet. Pupal weight ranged from 197.4 mg/pupa on tobacco, 233.1 mg/pupa on pepper and 253.4 mg/pupa on artificial diet. The average numbers of eggs laid by adults reared as larvae on the artificial diet, pepper, or tobacco were 614, 421 and 334 eggs/female, respectively. Numbers of remaining eggs in ovaries of the adult females reared as larvae on the artificial diet, pepper, or tobacco were 16, 26, and 42 eggs/female, respectively. The longevity of adult females developed from larvae reared on the three diets was not significantly different, whereas the longevity of male adults from the larvae reared on artificial diet was longer (16.8 d) than that for males reared on tobacco (13.8 d) and pepper (13.3 d). The intrinsic, finite, gross, and net rates of increase were highest for females reared as larvae on artificial diet, lowest for females emerging from larvae reared on tobacco, and intermediate for females emerging from larvae reared on pepper. Generation times and doubling time of H. assulta were shortest for larvae fed artificial diet, intermediate from larvae reared on pepper, and longest from larvae reared on tobacco. We concluded that the artificial diet was the most suitable larval diet of H. assulta followed by pepper, and tobacco.