Quantitative dietary requirements of the saw-toothed grain beetle,Oryzaephilus surinamensis,for l-leucine

Larvae of the saw-toothed grain beetle, Oryzaephilus surinamensis, were reared individually on meridic diets from hatching to adult emergence at 32±0·25°C and 75% r.h. These larvae developed little, if at all, and failed to carry out larval-pupal ecdysis on a diet devoid of leucine. Survival increased as the concentration of dietary l-leucine increased from 0·0 to 3·0 mg/g and rate of development, as l-leucine increased to 8·0 mg/g. With concentrations of dietary l-leucine greater than 8·0 mg/g, the rate of development of Oryzaephilus surinamensis decreased.     

Impact of live food on survival and growth of hatchery‐reared sea trout (Salmo trutta trutta L.) parr in the wild

Survival rates and growth parameters of hatchery‐reared sea trout (Salmo trutta trutta L.) fry were determined after stocking in the wild. The larvae were hatchery‐reared for 12 weeks in two groups: fry were fed either on live zooplankton and live chironomidae larvae (LFG), or fed a pellet diet (PFG). The survival rate and specific growth rates were higher in the LFG than in the PFG group. Most effective for hatchery‐reared fish intended for stocking was the natural, live feed. The mean number of chironomid larvae found in the stomachs of fish that were initially captured in the wild was significantly higher in the LFG than in the PFG group. The live diet supplied in the rearing period had a positive impact on the foraging skills of the sea trout fry and their survival in the wild after their release on 24 April 2010.     

Comparative food utilization of coffee bean weevil larvae on a new freeze-dried diet and green coffee beans

A meridic diet for culturing the coffee bean weevil, Araecerus fasciculatus was formulated and freeze-dried into pellets. When exposed to an atmosphere of 80 ± 5%r.h. the diet reached a moisture equilibrium that invoked oviposition and was satisfactory for growth and development of the insect. Larvae ingested larger amounts of the freeze-dried diet than of the natural food, green coffee beans, reaching equivalent weight and pupation in 31.8 ± 0.4 days on the diet as compared to 46.8 ± 0.8 days on the coffee beans. Approximate digestibilities of the two foods were not significantly different. However, the coffee beans were converted more efficiently to body mass than was the diet. Faeces of larvae on the diet contained more uric acid than those of larvae on coffee beans. Continuous culture and mass rearing of A. fasciculatus on the diet is possible.     

Fatty acid profile of the cabbage looper, Trichoplusia ni, and the effect of diet and rearing conditions

The fatty acids, palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (18:1), linoleic (18:2), and linolenic (18:3) were measured by GLC in Trichoplusia ni (Hübn.) from larvae reared on three different diets. The effect of rearing temperature and humidity on the levels of these fatty acids in pupae and pharate adults was determined. T. ni tended to accumulate 18:3 somewhat in proportion to its level in the diet. The respective levels (relative percentage) of this fatty acid in the diet and in the pupae were: bean leaves, 73·6 and 56·7; the diet based on lima beans, 10·2 and 3·5; and a meridic diet containing wheatgerm oil, 5·6 and 1·8. Pupae from larvae reared on a diet marginal in 18:3 content produced adults with deformed wings when reared at 30°C and normal wings when reared at 23 or 24°C, but there was no difference in their tissue level of 18:3. The phospholipids of last instar larvae, pharate pupae, pupae, pharate adults, and emerged adults are made up mostly of 18:0, 18:2, and 18:3 while the triglycerides of these stages contain relative large quantities of 16:0, 16:1, and 18:1. Pupal rearing temperature did not appear to influence the level of 18:3 in these two fractions enough to account for the degree of deficiency expressed as adult wing deformity. Both high (95%) and low (20%) relative humidity have an adverse effect on wing development but this effect can be overcome by 18:3 supplementation of the larval diet.     

Polyunsaturated fatty acid and sterol requirements of the southwestern corn borer, Diatraea grandiosella

The southwestern corn borer, Diatraea grandiosella, was reared on a meridic diet and its lipid requirements were determined. A dietary supplement of wheat germ oil was found to contain factors which were essential for larval growth and normal wing development. An investigation into the nature of these factors showed that linoleate or linolenate promoted normal wing development whereas β-sitosterol enhanced the larval growth rate.     

Selective Feeding of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hübner) and <Emphasis Type="Italic">Spodoptera litura</Emphasis> (Fabricius) on Meridic Diet with <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Toxins

Laboratory experiments were conducted to evaluate the behavior of Helicoverpa armigera (Hübner) and Spodoptera litura (Fabricius) larvae on meridic diet with different concentrations of Bt spray formulation Delfin or isolated Cry1Ac protein or the foliage and bolls from transgenic cotton, Bollgard hybrid RCH-317 Bt. Both insect species selectively fed on nontreated diet compared with the diet treated with Delfin. While H. armigera exhibited concentration response with Cry1Ac, this protein did not affect S. litura larvae. In general Helicoverpa selected diet with low concentrations (EC₂₀ and EC₅₀ levels) of Cry1Ac compared with higher concentrations of Cry1Ac. In order to develop appropriate management strategies, a thorough understanding of the behavioral mechanisms leading to the responses of insects to the proteins in transgenic varieties is required. Thus, based on results of the insects fed individually on the leaf discs or bolls from transgenic cotton plants alone or under choice situation with meridic diet revealed that H. armigera larvae preferred meridic diet to transgenic leaves or bolls expressing Cry1Ac protein. H. armigera larvae preferred meridic diet to plant material; more than 70% larvae were seen on the meridic diet, and average larval weight gain was in the range of 121.7–130.5 mg. However, in case of S. litura the larvae showed no significant discrimination between meridic diet and the leaf discs. In fact more than 60% larvae preferred leaf discs for feeding, though Cry1Ac expression in leaf discs was in the range of 0.9–2.18 μg/g. Thus differences in behavioral response could potentially impact the level of efficacy of crop cultivars that have been genetically engineered to produce these proteins.     

Photoperiodic response of larvae of the yellow-spotted longicorn beetle Psacothea hilaris after removal of the stemmata

The role of the stemmata in photoperiodism has been examined in holometabolic insects, but the only reliable results in Coleoptera have been obtained in Leptocarabus kumagaii (Carabidae), the larvae of which do not respond to photoperiod without stemmata. In the present study, photoperiodism was examined in another coleopteran, Psacothea hilaris (Pascoe) (Cerambycidae), after surgical removal of the stemmata. Larvae reared under short-day conditions and transferred to long-day conditions on day 2 of the 5th instar pupated without further larval molts, whereas those continuously reared under short-day conditions underwent supernumerary molts and did not pupate. When the stemmata were removed on day 2 of the 5th instar, the larvae pupated under long-day conditions but did not do so under short-day conditions. However, under long-day conditions some underwent supernumerary molts before pupation. Larvae from which the sensilla trichodeum were removed showed a similar response to that of stemmata-deficient larvae, and larvae from which stemmata were removed at a younger stage (day 2 of the 4th instar) responded to photoperiod similarly to intact larvae. Thus, supernumerary molts under long-day conditions after removal of the stemmata were attributed to injury due to surgery, rather than a change in photoperiodic photoreception. Therefore, we conclude that larvae of P. hilaris show a photoperiodic response after removal of stemmata, in contrast to larvae of L. kumagaii.     

Studies on the group effect in Acheta domesticus (L.) using artificial diets

Larvae of Acheta domesticus were reared on artificial diets both singly and in groups of six. The growth of group-reared larvae was significantly faster, and survival of singly reared larvae was greatly reduced. Survival of singly reared larvae was raised to that of grouped larvae when 1% wheat-germ oil was added to the diet. Wheat-germ oil also improved the growth of grouped larvae and of singly reared female larvae. The fatty acid composition of body lipid was similar, except for linolenic acid, whether the larvae were singly or group-reared, or whether wheat-germ oil was fed or not. These results are discussed from the point of view of the mechanism of the group effect.     

Starvation resistance of gypsy moth,Lymantria dispar (L.) (Lepidoptera: Lymantriidae): tradeoffs among growth,body size,and survival

Summary Survival and body composition of starving gypsy moth larvae initially reared on aspen foliage or artificial diet differeing in nitrogen (N) and carbohydrate concentration were examined under laboratory conditions. Diet nitrogen concentration strongly affected starvation resistance and body composition, but diet carbohydrate content had no effects on these. Within any single diet treatment, greater body mass afforded greater resistance to starvation. However, starving larvae reared on 1.5% N diet survived nearly three days longer than larvae reared on 3.5% N diet. Larvae reared on artificial diet survived longer than larvae reared on aspen. Differences in survival of larvae reared on artificial diet with low and high nitrogen concentrations could not be attributed to variation in respiration rates, but were associated with differences in body composition. Although percentage lipid in larvae was unaffected by diet nitrogen concentration, larvae reared on 1.5% N diet had a higher percentage carbohydrate and lower percentage protein in their bodies prior to starvation than larvae reared on 3.5% N diet. Hence, larger energy reserves of larvae reared on low nitrogen diet may have contributed to their greater starvation resistance. Whereas survival under food stress was lower for larvae reared on high N diets, growth rates and pupal weights were higher, suggesting a tradeoff between rapid growth and survival. Larger body size does not necessarily reflect larger energy reserves, and, in fact, larger body size accured via greater protein accumulation may be at the expense of energy reserves. Large, fast-growing larvae may be more fit when food is abundant, but this advantage may be severely diminished under food stress. The potential ecological and evolutionary implications of a growth/survival tradeoff are discussed.     

Interactions between Nosema pyrausta (Microsporidia: Nosematidae) and Bacillus thuringiensis subsp. kurstaki in the European corn borer (Lepidoptera: Pyralidae).

Larval susceptibility to Bacillus thuringiensis was determined for Nosema pyrausta-infected and uninfected European corn borers, Ostrinia nubilalis (Hübner), in bioassays using a commercial formulation of B. thuringiensis subsp. kurstaki, Dipel ES, incorporated into diet. LC50 values for N. pyrausta-infected larvae were significantly lower (P<0.0001) than for uninfected larvae and declined with increasing levels of infection. LC50 values for a 15-d bioassay using field-colony first instars were 0.006 and 0.027 mg of Dipel ES/kg of diet for larvae moderately infected by N. pyrausta and uninfected larvae, respectively. Nosema pyrausta-infected larvae reared on Dipel ES-amended diets produced 70-fold fewer spores (P<0.0001) than larvae reared on standard diet. For example, 15 d after placement as first instars on standard diet, infected field-colony larvae produced 7.6-8.7 million N. pyrausta spores per larva; similar larvae placed on diet containing 0.09 mg of Dipel ES/kg of diet produced 85-103 thousand spores per larva. Infected larvae also weighed less and failed to mature on Dipel ES-amended diets. Increased susceptibility of N. pyrausta-infected larvae to Dipel ES and reduced N. pyrausta spore production in larvae feeding on diet containing Dipel ES suggest that Bt corn will have a direct adverse effect on the survival and continual impact of N, pyrausta as a regulating factor on European corn borer populations.     

Interactive effect of diet and temperature on instar numbers in Spodoptera litura,with reference to head capsule width and weight

The effects of diet and temperature on instar numbers and head capsule width in Spodoptera litura F. were compared among individuals reared on an artificial diet, lettuce and perilla leaves at 25 and 30 °C. The number of instars that the insect completed varied as diet and temperature were changed. All the larvae developed through seven instars at 25 °C regardless of diet, but at 30 °C, the number of instars varied depending on the diet. All larvae fed on lettuce leaves had six instars, while larvae fed on the artificial diet passed through seven instars. On perilla, 52% of larval individuals had six instars, and the rest had seven instars. Head capsule width could be used effectively to determine the developmental stage of individual larvae. The frequency distribution of head capsule width showed six or seven distinct peaks, depending on diet and temperature conditions. The relationship between mean head capsule width and weight of larvae was described using an exponential model.     

Effect of rearing Cactoblastis cactorum on an artificial diet on the behaviour of Apanteles opuntiarum

Cactoblastis cactorum's unintended arrival to Florida and its expansion in North America represent a threat to Opuntia-based agriculture and natural ecosystems in the United States and Mexico. Apanteles opuntiarum attacks C. cactorum and is a potential biocontrol agent due to its specificity, wide distribution and occurrence. Laboratory rearing methods using excised cladodes for C. cactorum as host larvae of A. opuntiarum were developed, but require a continuous supply of cactus with a risk of microorganisms compromising the rearing. Host cues —including odour of host metabolic subproducts like faeces and chemicals emitted by the attacked plant— are the most important signals that help a parasitoid locate a host. Little attention has been paid to behavioural differences of parasitoids in the presence of hosts reared on artificial diet. Thus, the aims of the present work were to determine the effect of meridic diet for C. cactorum on parasitoid behaviour and to determine whether prior experience (previous exposure to stimuli) influences the response of A. opuntiarum towards hosts. Parasitism rates were assessed using cladodes or meridic diet as larvae food source. Behavioural experiments also evaluated the effect of prior experience (larvae or frass from larvae fed on cactus or diet) on host searching, encounter and attack of different stimulus (larvae or frass from larvae fed on cactus or diet). Parasitism behaviour of A. opuntiarum was negatively affected by the use of meridic diet to feed host larvae. Presenting parasitoids with larvae rather than their frass influenced excitatory behavioural responses in terms of contact, probing and stinging in A. opuntiarum females, whereas the effect of prior experience on the behaviours was not quite consistent. For laboratory mass-rearing procedures of A. opuntiarum, we recommend previous contact of females with frass from cactus-fed larvae and a piece of cactus, which showed enhanced parasitism rates.     

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.     

The regulation of development during diapause in Ephestia elutella (Hübner) by temperature and photoperiod

Diapausing larvae of Ephestia elutella reared at 20°C in short photoperiods (LD 11:13), and then maintained 12 weeks or longer at 5–15°C before transfer to 20 or 25°C, pupated sooner than unchilled controls. At 25°C, all samples kept in long photoperiods (LD 15:9) survived better and pupated faster than similarly treated samples held in short photoperiods (LD 9:15). Samples kept at 20°C after chilling pupated much slower than those at 25°C, and, except after exposure at 5°C, pupated at similar rates at LD 11:13 or 15:9, although mortality was higher at the shorter photoperiod. After exposure at 5°C, larvae required increased day-length as well as increased temperature to hasten pupation whereas after exposure at 10°C most responded to increased temperature only.For samples maintained in slightly heated or unheated outbuildings, the summer emergence was poorly synchronized and males on average emerged ahead of females. Samples moved from the unheated outbuilding to 25°C and long days in the laboratory in early spring, however, pupated quickly and males and females emerged together. A late phase of diapause development thus exists requiring both high temperature and long photoperiods to ensure a prompt resumption of morphogenesis. Spring temperatures in the United Kingdom are seldom high enough to synchronize the completion of diapause.     

Life Cycle of the Mulberry Longicorn Beetle,Apriona germari Hope on an Artificial Diet

Mulberry longicorn beetle, Apriona germari, was reared on an artificial diet to investigate its life cycle. Average egg period was 17.95 days. Most larvae pupated at the 8th (33.3%) or 9th (33.3%) instars, but others emerged from the 7th to the 11th instars. The total duration of larval stage from the 1st to the end of the 9th and the 11th instars were 176.2 and 251.5 days, respectively. For terminatiopn of diapause and acceleration of pupation, low temperature treatment at 5°C for 60 days was highly effective. Average pupal period for female and male was 19.3 and 18.4 days, respectively. Average longevity of adults was similar with 40.5 days for female and 44.3 days for male. Mating had occurred from about 10 days after the adult emergence, and then a female adult laid one or two eggs per day. Average number of eggs oviposited by a female was approximately 47.7. Total life span of A. germari, when reared on an artificial diet in the laboratory, ranged broadly from 197.5 days to 331.5 days mainly depending on the larval period.     

Developmental changes in urea concentrations in the haemolymph of Daizo (T), an original strain of the silkworm,Bombyx mori reared on an artificial diet and on fresh mulberry leaves

Urea concentrations in the haemolymph of Daizo (T), an original strain of the silkworm, Bombyx mori, reared on an artificial diet and on fresh mulberry leaves were determined by a urease-indophenol method during the larval-pupal-adult development. Urea concentrations in the fourth and fifth instar larvae reared on an artificial diet (diet I) were between 0.10 and 0.15 mg urea N/ml haemolymph, and increased during the larval-pupal transformation to reach 0.33 mg/ml at the larval-pupal ecdysis. A further increase was observed during pupal-adult development and finally reached 0.48 mg/ml at day 7 pharate adult. In the fourth and fifth instar larvae reared on fresh mulberry leaves, the concentrations were low (0.05 mg/ml). From the larval-pupal ecdysis until day 8 pharate adult, further low urea concentrations (0.04 mg/ml) were observed. By starvation from 72 hr of the fifth instar larvae reared on another artificial diet (diet II), the elevation of urea concentrations (between 1.4- and 3.0-fold against the controls) was observed from just after starvation until day 1 spinning. From day 5 pupae, both the starved and the control insects showed a marked elevation of urea concentrations in the haemolymph, which was never observed on animals reared on diet I.     

Growth and development of the knapweed root weevil,Cyphocleonus achates,on a meridic larval diet

Cyphocleonus achates, the knapweed weevil, is an effective biological control agent of the invasive weed, Centaurea maculosa Lam. A meridic diet was developed and tested for the rearing of the larval stage of this insect. Using this diet, C. achates was reared for over three generations, with the adults being offered knapweed plants for feeding and oviposition in greenhouse conditions. Slight or no differences were seen between insects reared on a standard meridic diet formulation and one containing knapweed tissues. The following life history parameters were monitored over the three generations: percent egg hatch (ranging from 42.9 to 59.1%), time to egg hatch (20.0–23.2 days), time to adult emergence (52.0–54.1 days), adult weights 3 days post-eclosion (101.9–117.0 mg), percent adult emergence (48.3–58.6%), and percent mortality/deformity in the different stages (with mortality occurring primarily in the early larval stages). Additionally, a study involving low temperature and short day conditions suggested that C. achates could be maintained for longer periods of time in larval diet cells when placed in growth-retarding conditions, although percent adult emergence was lower. External morphology was also studied in order to distinguish between the sexes to ensure that each adult cage had a similar ratio of females to males. Abdominal features were found to be the most dependable characteristics for use when determining the sex of adult C. achates.     

Bioassay of a β-exotoxin of Bacillus thuringiensis against Heliothis zea larvae

A β-exotoxin of Bacillus thuringiensis was bioassayed on 1st-, 3rd-, and 4th-instar Heliothis zea larvae. Larvae were fed continuously on diet incorporated with concentrations of 1–700 μg AI/ml diet. Larval and/or pupal death was the measured response criterion. Dosage-mortality responses were determined at two evaluation times, 7 days post-initiation and after the entire larval-pupal development period, using probit analysis procedures. The LC₅₀ values for 1st-, 3rd-, and 4th-instar larvae at these two evaluation times were 4.9, 134.6, and 286.2 μg AI/ml diet, and 4.0, 17.6, and 66.4 μg AI/ml diet, respectively. Differences in responses between instars were more pronounced at 7 days than after the entire development period. The LT₅₀ values for 1st-, 3rd-, and 4th-instar larvae decreased from 7.1 to 3.1, 12.7 to 5.4, and 11.6 to 5.2 days post-initiation, respectively, as dosages were increased. The toxin did not act as a feeding deterrent, as all increases in dosage caused increases in mortality. Nineteen and 38% of those 3rd- and 4th-instar larvae, respectively, which survived β-exotoxin intoxication pupated later than untreated cohorts.     

Inorganic ion composition of haemolymph of the cecropia silkmoth: changes with diet and ontogeny

The levels' of sodium, potassium, magnesium, calcium, chloride, trehalose, and osmotic pressure in haemolymph were studied during ontogeny in the silkmoth Hyalophora cecropia, reared on either foliage or an artificial diet. Potassium and calcium in haemolymph changed little with ontogeny or diet, and averaged 35 and 10 m-equiv/l., respectively. The haemolymph levels of sodium and chloride were greater in larvae fed on artificial diet than in those on foliage, reflecting the levels in the respective diets; after cessation of feeding, the levels in haemolymph of the two groups approached common values (sodium 1–2 m-equiv/l.; chloride 20 m-equiv/l.). Magnesium was higher in haemolymph of foliage-fed larvae (100 m-equiv/l.) than in diet-fed larvae (65 m-equiv/l.), and in both groups declined after spinning to an average level of 40 m-equiv/l.Haemolymph from fifth instar Manduca sexta larvae reared on an artificial diet had ion levels very close to those in Cecropia similarly reared. Haemolymph of Danaus plexippus at three stages of development was also similar, but showed some quantitative differences from the other species.     

Bionomics of the parasitoid Apanteles taragamae as influenced by different diets fed to its host,Maruca vitrata

The parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) has been introduced into Benin by the International Institute of Tropical Agriculture (IITA-Benin station) from Taiwan in an attempt to control the cowpea pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a serious pest of flowers and pods of cowpea Vigna unguiculata Walp. (Leguminosae: Fabaceae). Both the pest and its parasitoid are currently mass-reared using a cowpea and maize flour-based meridic diet. In this study, the suitability of germinating seeds from three cowpea varieties, Kpodji-guèguè, Tawa and TVX3236, as substrates, was tested for rearing A. taragamae under laboratory conditions. The seeds that were soaked for 48 h were the most suitable for M. vitrata larval rearing with up to 87 % survival. The highest parasitism rate of M. vitrata larvae by A. taragamae was observed on the local variety Tawa. Compared to meridic diet, the development cycle of the parasitoid was shorter on Tawa sprouts which also lead to the highest lifetime fecundity. The parasitoid sex ratio varied significantly between feeding substrates with a higher proportion of female wasps on the improved varieties TVX2336 and local variety Kpodji-guèguè. Rearing M. vitrata larvae on germinating cowpea grains is 4.38 times cheaper than on meridic diet. The data are discussed with emphasis on the effects of feeding substrates quality on life history parameters of insect pests and their parasitoids.