Laboratory environment effects on the reproduction and mortality of adult screwworm (Diptera: Calliphoridae)

The New World screwworm, Cochliomyia hominivorax Coquerel, is mass reared for screwworm eradication initiatives that use the sterile insect technique. New methods for rearing have helped to reduce the cost of the eradication program. We examined the effect and interaction of three temperatures (24.5, 29.5 and 34.5 degrees C), two diets (2% spray-dried blood plus 0.05% vitamins and corn syrup carrageenan) and three population densities (300, 400, and 500 flies/cage) on egg production, egg hatch, number of observable fertilized eggs, mortality (male and female) and ovarian development. The three population densities did not affect any of the parameters monitored. Using the protein diet increased egg production at all temperatures. Diet did not affect egg hatch or female mortality. Male mortality was significantly greater when fed the protein diet and reared at 24.5 degrees C and 34.5 degrees C. Egg hatch was significantly less when the flies were reared at 34.5 degrees C. When exposed to high temperatures (37 degrees C and 40 degrees C) egg production, egg hatch, fertility and mortality were adversely affected. At the higher temperatures, yolk did not adequately form during oogenesis. When compared to the normal rearing photoperiod (12 L:12 D), short photoperiod (1 L:23 D) increased egg production, egg hatch and fertility but lowered mortality.     

THE INFLUENCE OF DIETARY α‐SOLANINE ON THE WAXMOTH Galleria mellonella L

Plant allelochemicals are nonnutritional chemicals that interfere with the biology of herbivores. We posed the hypothesis that ingestion of a glycoalkaloid allelochemical, α‐solanine, impairs biological parameters of greater wax moths Galleria mellonella. To test this idea, we reared wax moths on artificial diets with 0.015, 0.15, or 1.5 mg/100 g diet of α‐solanine. Addition of α‐solanine to the diet affected survival of seventh‐instar larvae, pupae, and adults; and female fecundity and fertility. The diet containing the highest α‐solanine concentration led to decreased survivorship, fecundity, and fertility. The diets supplemented with α‐solanine led to increased malondialdehyde and protein carbonyl contents in midgut and fat body and the effect was dose‐dependent. Dietary α‐solanine led to increased midgut glutathione S‐transferase activity and to decreased fat body glutathione S‐transferase activitiy. We infer from these findings that α‐solanine influences life history parameters and antioxidative enzyme activities in the midgut and fat body of G. mellonella.     

Dietary complementation across life stages in the polyphagous lady beetle Coleomegilla maculata

We investigated the life history consequences of changes in diet between larval and adult life stages in the polyphagous lady beetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae). Beetles were reared on three larval diets: greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae), eggs of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), and bee pollen. The reproductive performance of females was then evaluated on an adult diet of either greenbug or moth eggs. Moth eggs appeared to be the most suitable diet for larvae, yielding the largest adults, and pollen the least suitable, resulting in the smallest adults and greatly extended developmental time. Pollen‐reared beetles tended to have lower fecundity and fertility than those reared on animal protein, regardless of adult diet. Female fitness was generally increased by a change in diet upon emergence to the alternative source of animal protein, suggesting that dietary complementation occurred across life stages. Among females reared on greenbug, a change of diet to moth eggs reduced the period required for production of 12 clutches and increased egg fertility compared to continued feeding on greenbug. Among females reared on moth eggs, a change of diet to greenbug increased fecundity compared to continued feeding on moth eggs. Among females fed an adult diet of greenbug, those fed moth eggs as larvae had faster production of 12 clutches and higher fecundity. We discuss these novel results in the context of coccinellid life history and ecology and their potential implications for other insects that are predatory as both larvae and adults.     

THE EFFECTS OF XANTHOTOXIN ON THE BIOLOGY AND BIOCHEMISTRY OF Galleria mellonella L. (LEPIDOPTERA: PYRALIDAE)

The effects of a dietary plant allelochemical, xanthotoxin (XA), on survivorship, development, male and female adult longevity, fecundity, and hatchability of the greater wax moth Galleria mellonella L. were investigated. Oxidative stress indicators, the lipid peroxidation product, malondialdehyde (MDA), and protein oxidation products, protein carbonyl (PCO) contents, and activities of a detoxification enzyme glutathione S‐transferase (GST) activity were determined in wax moth adults. The insect was reared from first‐instar larvae on an artificial diets containing XA at 0.001, 0.005, or 0.1% to adult stage in laboratory conditions. Relative to the controls, the diets containing XA concentrations led to decreased survivorship in seventh instar, pupal, and adult stages. Compared to control diet (77.7%), the highest dietary XA concentration decreased survivorship to adulthood to 11.0%. The highest XA concentration (0.1%) reduced female longevity from 10.4 to 5.7 days and decreased egg numbers from 95.0 to 33.5 and hatchability from 82.7 to 35.6%. The lowest XA concentration (0.001%) led to about a sixfold increase in MDA content. XA at high concentrations (0.005 and 0.1%) increased MDA (by threefold) and protein carbonyl (by twofold) contents decreased GST activity. The highest dietary XA concentration decreased GST activity from 0.28 ± 0.025 to 0.16 ± 0.005 μmol/mg protein/min. We infer from these findings that XA‐induced oxidative stress led to decreased biological fitness.     

Linking larval nutrition to adult reproductive traits in the European corn borer Ostrinia nubilalis

Throughout an organism's lifetime, resources are strategically allocated to many different functions, including reproduction. Reproduction can be costly for both sexes; females produce nutrient‐rich eggs, whereas males of many species produce large and complex ejaculates. In capital breeding insects, nutrients are mainly acquired during the larval period, yet allocation decisions impact the reproductive fitness of adults. The present study examines the effect of larval dietary nitrogen on both male and female reproductive traits in the European corn borer moth Ostrinia nubilalis Hübner, whose adults do not feed and whose males transfer a large, nitrogen‐rich spermatophore. One day post‐eclosion, O. nubilalis adults reared on one of three different diets (3.0%, 1.6%, or 1.1% nitrogen) are mated and two experiments are undertaken: one to measure nitrogen and carbon content of male ejaculates, and the other to determine female fecundity and fertility. Although male larval diet does not alter the percentage nitrogen content of adult somatic tissue, males reared on the higher nitrogen diet (3.0%) produce spermatophores with increased nitrogen relative to somatic nitrogen. Furthermore, females raised on the 3.0% nitrogen diet receive spermatophores with lower carbon : nitrogen ratios and thus more nitrogen. Overall, females lay more eggs as their larval dietary nitrogen increases, although they lay fewer eggs when their mates are raised on the higher (3.0%) nitrogen diet. This suggests that O. nubilalis females may use male‐derived nitrogen not to supplement egg production, but rather for somatic maintenance. Overall, the present study furthers our understanding of how larval diet can affect adult fitness in Lepidoptera.     

Mating behaviour in Oncopeltus fasciatus (Dallas): effects of diet, photoperiod, juvenoids and precocene II

ABSTRACT. When adults of the large milkweed bug, Oncopeltus fasciatus (Dallas) were starved or fed non-host seeds, their mating activity during the 30 days following emergence was reduced by c. 50%. Topical applications of a juvenoid to adults fed non-host seeds usually increased mating activity, sometimes to near the level of milkweed-fed controls. An optimal juvenoid dose applied to adults reared and fed on sunflower seeds increased mating activity by only 9% to 28% from that of controls reared and fed on milkweed. Rearing and maintenance of the sexes on separate diets before pairing indicated that both the juvenoid-restored and non-restored milkweed stimulatory effects on mating probably acted exclusively on the males. Topical application of the anti-allatotropic agent precocene II to milkweed-fed males reduced mating activity by 75%. Simultaneous juvenoid treatment prevented most, but not all, of the precocene II effect. Juvenoid treatment completely prevented the depressed mating activity under short days. Rearing and maintenance of the sexes under different photo-periods before pairing under short days showed that photoperiod acted solely on the males. It is postulated that JH and one or more photosensitive and diet-sensitive factors in males regulate mating activity, JH being stimulatory but nonessential. A partial dietary control over mating may optimize male activity according to the population density and female reproductive activity.     

Reproductive responses to photoperiod and temperature by diapausing and nondiapausing populations of Sesamia nonagrioides Lef. (Lepidoptera − Noctuidae)

Abstract.  The influence of long- and short-day cycles on ovipostion and egg hatch of the corn stalk borer, Sesamia nonagrioides were investigated at a range of temperatures. Oviposition was suppressed when insects are exposed to long days through their immature stages and then transferred to short days after mating. Moreover, mean oviposition and egg hatch increased from 15 to 27.5 °C, whereas oviposition declined significantly at 30 °C at both photoperiodic regimes. Females derived from a diapausing population exposed to long days after mating showed a significantly higher egg production compared to females derived from a nondiapausing population. However, when females from a diapausing population were left to oviposit under short days, fewer eggs were produced compared to those exposed to long days after mating. Thus, photoperiod appears to affect reproductive traits of this species in a quantitative manner. Larval diapause duration is positively correlated with fecundity of the adults. There is also a positive correlation between pupal weight of individuals derived from a diapausing population and the postdiapause fecundity of adults.     

Seminal fluid causes temporarily reduced egg hatch in previously mated females

In Drosophila, male accessory gland fluid (seminal fluid) has multiple effects on the female's reproductive efficiency. Here, we show the effect of seminal fluid on rate of egg hatch immediately following mating. Singly mated females were remated to two classes of sterile males, one with seminal fluid and one without seminal fluid. Transfer of seminal fluid results in a strong reduction in egg hatch shortly after the mating. Also, it is shown that remating with normal males causes an immediate reduction of egg hatch followed by recovery to normal egg hatch. In all cases, unhatched eggs contained no sperm. These results are consistent with a role for seminal fluid in sperm competition, mediated by incapacitation or inefficient use of resident sperm.     

Oil-soluble dyes incorporated in meridic diet of Diatraea grandiosella (Lepidoptera: Crambidae) as markers for adult dispersal studies

Mark-release-recapture experiments to study insect dispersal require the release of marked insects that can be easily identified among feral conspecifics. Oil-soluble dyes have been used successfully to mark various insect species. Two oil-soluble dyes, Sudan Red 7B (C.I. 26050) and Sudan Blue 670 (C.I. 61554), were added to diet of the southwestern corn borer, Diatraea grandiosella Dyar, and evaluated against an untreated control diet. Survival, diet consumption, larval and pupal weight, development time, fecundity, longevity, and dry weight of the adults were measured. Adults reared on the three diets were also tested for mating success. Some minor effects were observed for southwestern corn borers reared on the marked diets. Eggs, larvae, pupae, and adults were all reliably marked and readily identifiable. Adults retained color for their entire life span. Adults from each diet mated successfully with adults from the other diets. F1 progeny from the different mating combinations survived to the second instar but tended to lose the marker after 3-4 d on untreated diet. Both Sudan Red 7B and Sudan Blue 670 can be used to mark southwestern corn borer adults and thus should be useful for mark-release-recapture dispersal studies. The dyes will also be useful for short-term studies with marked larvae and oviposition behavior.     

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.     

Sterilisation of the potato moth, Phthorimaea operculella (Lepidoptera: Gelechiidae) by fumigation with thiotepa

The chemosterilant thiotepa was used in fumigation chambers for sterilisation of male and female potato moths. Its effectiveness was registered by recording egg production, egg hatch, longevity of moths, and mating frequency. Also studied was the effect on the persistence of the chemical of temperature, exposure time and concentration. The tests showed that it was possible to sterilise fully male and female moths with thiotepa without adverse effects on mating and longevity. Generally, males were more susceptible to sterilisation than females. No definite relationship was found between dosage and egg production, longevity and mating frequency of moths. The compound did not lose its sterilising activity when used successively up to five times during the same day or once weekly for a total of 4 wk. The sterilising activity was related to temperature, exposure time, concentration and rates of airflow of the circulatory fumigation chambers. Some reduction of fertility occurred when F, adults paired with untreated moths.     

Effect of plant oils on quality parameters of Bactrocera tryoni (Froggatt) reared on liquid larval diet

Liquid larval diets have been developed for several tephritid fruit flies including Queensland fruit fly, Bactrocera tryoni (Frogatt) (Q‐fly). In liquid diets, wheat germ oil (WGO) is usually added to improve performance in some quality parameters of reared flies, especially flight ability. However, for some flies, other plant oils may be more readily available, cheaper or produce flies of superior performance. In the present study, four alternative types of plant oils – rice bran, canola, vegetable, and sesame – were incorporated into a fruit fly liquid larval diet to replace the currently used wheat germ oil and their efficacy on the quality parameters of reared Q‐fly was compared to diets containing wheat germ oil or no oil. The quality parameters included: total pupal yield (N), pupal recovery (%), larval duration (days), pupal weight (mg), adult emergence (%), adult fliers (%), rate of fliers (%), sex ratio (%), F₁ egg/female/day and egg hatching (%). There were significant differences among treatments in performance of Q‐fly. Vegetable oil appeared better in terms of total pupal yield, percentage of pupal recovery, percentage of adult emergence, percentage of fliers, mean egg/female/day and % F₁ egg hatch compared with other oil treatments, especially from that of WGO treated diet. The result suggests that WGO can be substituted with rice bran and vegetable oil to improve the liquid larval diet for rearing of B. tryoni, with vegetable oil being the best replacement.     

Disparity in sexual behaviour between wild and mass‐reared Mexican fruit flies

The sterile insect technique (SIT) is currently used to control Mexican fruit fly Anastrepha ludens Loew (Diptera: Tephritidae). However, mass‐rearing can alter the quality of released males. If males that are mass‐reared have behaviours different from those of their wild counterparts, then this may diminish the effectiveness of SIT. Questions remain as to whether wild females may be able to detect the male condition before, during and/or after copulation with a mass‐reared male. In the present study, copula duration, female remating, female fecundity and fertility of both mass‐reared and wild A. ludens are evaluated. Marked differences are found between mass‐reared and wild females. Specifically, mating latency is longer and copula duration is shorter for wild females compared with mass‐reared females. Importantly, there are no significant differences in mating latency, copula duration or remating probability between wild females paired with either mass‐reared or wild males. All mass‐reared females remate, whereas only approximately half of the wild females remate after first mating with either a wild or mass‐reared male. Fecundity of wild females mated to either wild or mass‐reared males is approximately one‐third lower than that of mass‐reared females, confirming that mass‐reared females may have been selected for high fecundity and are adapted to laboratory conditions. Fertility of females that mate with a wild male for only 10 min is not significantly different from that achieved via a full‐length copulation. By contrast, females mating with mass‐reared males need copulation durations of at least 40 min to achieve fertility comparable with that achieved via a full‐length copulation. The findings of the present study have important implications for A. ludens controlled through SIT and broaden our understanding on the copulatory and post‐copulatory behaviours between wild females and mass‐reared males.     

Wheat germ oil and its effects on a liquid larval rearing diet for oriental fruit flies (Diptera: Tephritidae)

Wheat germ oil was added to a larval liquid diet for rearing Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) to optimize fruit fly quality. Effects of various concentrations of wheat germ oil at 0.04, 0.07, 0.15, 0.30, and 0.66% and their possible mode of action were evaluated. Results suggest that addition of wheat germ oil does not affect pupal weight, larval developmental period, adult emergence, mating ability, or peak time for egg production. But there was a significant increase in pupal recovery, percentage of adult fliers, egg production, or egg hatch for larvae fed the diet with wheat germ oil compared with those reared on the liquid diet without wheat germ oil. The increase in egg hatch and fliers was dose dependent. Therefore, addition of wheat germ oil to fruit fly rearing diet is a novel way to improve fruit fly quality, especially in egg hatch, fliers, egg production, and pupal recovery.     

Ingestion of the anti‐bacterial agent,gemifloxacin mesylate,leads to increased gst activity and peroxidation products in hemolymph of Galleria mellonella l. (lepidoptera: pyralidae)

Gemifloxacin mesylate (GEM) is a synthetic, fourth‐generation fluoroquinolone antibacterial antibiotic that has a broad spectrum of activity against bacteria. GEM inhibits DNA synthesis by inhibiting DNA gyrase and topoisomerase IV activities. Recent research into insect nutrition and mass‐rearing programs, in which antibiotics are incorporated into the culture media to maintain diet quality, raised a question of whether clinical antibiotics influence the health or biological performance of the insects that ingest these compounds. Because some antibiotics are pro‐oxidant compounds, we addressed the question with experiments designed to assess the effects of GEM (mesylate salt) on oxidative stress indicators, using Galleria mellonella larvae. The insects were reared from first‐instar larvae to adulthood on artificial diets amended with GEM at 0.001, 0.01, 0.1, or 1.0%. Feeding on the 1% diets led to significantly increased hemolymph contents of the lipid peroxidation product, malondialdehyde and protein oxidation products, protein carbonyl. All GEM concentrations led to increased hemolymph glutathione S‐transferase activity. We inferred that although it was not directly lethal to G. mellonella larvae, dietary exposure to GEM exerts measurable oxidative damage, possibly on insects generally. Long‐term, multigenerational effects remain unknown.     

Effect of mating on survival at low temperature in females of the Japanese common grass yellow,Eurema mandarina

1. In some insects that overwinter as adults, mating occurs both before and after overwintering. Two hypotheses have been proposed to explain the adaptive significance of pre‐overwintering copulation of females. One is the bet‐hedging hypothesis, which explains pre‐overwintering copulation as a preparation for less chance of mating in the following spring. The other is the nuptial gift hypothesis, which states that secretions derived from males increase overwintering success of females. 2. In Eurema mandarina, both diapause autumn‐ and non‐diapause summer‐form male adults emerge with autumn‐form female adults in the last generation in a year. Most autumn‐form females mate with summer‐form males before winter, and re‐mate with autumn‐form males in the following spring. Because autumn‐form females have sufficient chances for mating after overwintering, the nuptial gift hypothesis has been regarded as the more probable hypothesis. 3. To test the nuptial gift hypothesis, the survival period was compared under short‐day conditions at 10 °C between mated and unmated females that had been reared on sucrose solution at 25 °C for 15–21 days. The mated females had significantly greater longevity than the unmated females, supporting the nuptial gift hypothesis. Body size also affected the survival period. 4. The results suggest that the nuptial gift is an important factor for the evolution of pre‐overwintering copulation in species in which females mate both before and after overwintering.     

Exuviae eating: a nitrogen meal?

Many insects eat their cast cuticle (exuviae) after moulting. The functional significance of this behaviour has not been addressed experimentally. I tested the hypothesis that exuviae eating constitutes a meal, so the animal recycles its nitrogen content. Nitrogenous compounds (protein and chitin) are major components of the cuticle in Periplaneta americana, accounting for as much as 87% of the total weight. It was found that insects almost invariably ate their exuviae during their larval life. The frequency of the behaviour decreased in newly emerged adults and varied between the sexes, males eating their exuviae less frequently than females. This may be due to the extra nitrogen endowment which females need for reproduction. Aposymbiotic animals, which lack the supply of essential amino acids from endosymbiotic bacteria, always ate their exuviae regardless of sex. When animals were reared on different diets throughout their larval life protein level in the diet correlated with exuviae eating. Animals reared on a low protein diet showed the highest levels of exuviae eating; animals reared on a high protein diet showed the highest levels of exuviae rejection. Analysis of the frass produced after exuviae meals showed that over 58% of the nitrogen present in the exuviae was recycled. This demonstrated that cockroaches digested nitrogenous compounds contained in the cuticle. The possibility that the exuviae meal has other functions is discussed, although the evidence supports a nutritional role.     

Life‐history trade‐offs under different larval diets in Drosophila suzukii (Diptera: Drosophilidae)

Most larval drosophilids eat the microorganisms that develop in rotting fruit, a relatively protein‐rich resource. By contrast, the spotted‐wing Drosophila suzukii Matsumara (Diptera: Drosophilidae) uniquely develops in ripening fruit, a protein‐poor, carbohydrate‐rich resource. This shift in larval nutritional niche has led to D. suzukii being a significant agricultural pest in the U.S.A. and Europe. Although occupying a new niche may benefit a species by reducing competition, adaptation in host use may generate trade‐offs affecting fitness. To test the hypothesis that fitness trade‐offs will change with adaptation to novel larval diets, D. suzukii larval development on either a diet of a fresh, ripe blueberry (a natural host) or standard artificial Drosophila media (protein‐rich) is compared and the effect of diet on development time from egg to adult, adult body size and male wing spot area, and female fecundity is assessed. Larval development time differs, with larvae on the blueberry emerging as adults earlier than those on the artificial medium, although other fitness measures do not vary between the two diets. In addition, the faster development time on a blueberry does not trade off with body size as expected, although early fecundity is delayed in females that develop on blueberries. Thus, adaptation to a novel larval diet environment does not come at a cost to the ability to develop in protein‐rich resources.