Greenhouse Evaluation of Dose– and Time–Mortality Relationships of Two Nucleopolyhedroviruses for the Control of Beet Armyworm, Spodoptera exigua, on Chrysanthemum

Dose– and time–mortality relationships of baculoviruses in pest insects are important for the determination of effective spraying regimes. A series of experiments with Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) and Spodoptera exigua MNPV (SeMNPV) against synchronized populations of S. exigua larvae in greenhouse chrysanthemum was conducted. Dose– and time–mortality relationships of different virus concentrations and S. exigua target stages were determined and the area foliage consumption was measured. Crop injury was greatly reduced when S. exigua were controlled as second or third instar larvae, whereas virus applications against fourth instar larvae could not prevent considerable crop injury, even at high concentrations. SeMNPV was approximately 10 times as infectious as AcMNPV when applied on greenhouse chrysanthemum. The relative virulence of AcMNPV and SeMNPV corresponded reasonably well with previously published laboratory bioassay data. SeMNPV killed second and fourth instar S. exigua larvae approximately 12 h faster than did AcMNPV in chrysanthemum, but no difference in speed of action was found for third instar larvae. The relative speed of action of AcMNPV and SeMNPV determined in chrysanthemum and in laboratory bioassays did not correspond for third instar S. exigua larvae; laboratory bioassay data can therefore not simply be extrapolated to the crop level.     

Validation of a Comprehensive Process-Based Model for the Biological Control of Beet Armyworm,Spodoptera exigua,with Baculoviruses in Greenhouses

This paper describes the validation and sensitivity analysis of a process-based simulation model (BACSIM) for the control of beet armyworm, Spodoptera exigua, with baculoviruses. Model predictions are compared to results of independent greenhouse experiments in which second, third, or fourth instar larvae of S. exigua in chrysanthemum plots are treated with different concentrations of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) and S. exigua MNPV (SeMNPV), two viruses with distinct differences in infectivity and mean time to kill. BACSIM provides robust predictions for the control of S. exigua populations in greenhouse chrysanthemum with both AcMNPV and SeMNPV. Mortality levels caused by AcMNPV and SeMNPV were generally predicted within a 25% margin of error compared to the observed values. None of the deviations was higher than 40%. All values of simulated foliage consumption, caused by S. exigua populations treated with AcMNPV or SeMNPV applications, fell within 95% confidence intervals of measurements. Simulated time to kill was, in general, lower than the measurements. This discrepancy may be caused by the behavior of S. exigua larvae which feed on the underside of chrysanthemum leaves where they are protected from polyhedra. This suggests that the larval foraging behavior may play an important role in the efficacy of baculovirus applications and should be further studied experimentally. This validated model can be used for the pretrial evaluation of the efficacy of genetically modified baculoviruses as biological control agents and for the optimization of spraying regimes in chrysanthemum cultivation.     

Effect of tinopal LPW on the insecticidal properties and genetic stability of the nucleopolyhedrovirus of Spodoptera exigua (Lepidoptera: Noctuidae)

The influence of an optical brightener, Tinopal LPW, on the activity of a purified genotype of the nucleopolyhedrovirus (SeMNPV) of the beet armyworm, Spodoptera exigua (Hübner), was determined in second to fifth instar (L2-L5) S. exigua. When mixed with viral occlusion bodies (OB) 1% Tinopal LPW significantly reduced the median lethal dose (LD50) of the virus in all instars compared with insects treated with SeMNPV alone. Levels of enhancement, as determined by LD50 values, ranged from 2.6- to 580-fold, depending on the instar. The greatest enhancement occurred on the two later instars, L4 (70-fold) and L5 (580-fold), which show a much higher resistance to SeMNPV infection than earlier instars. The median time to death (MTD) values were not significantly different in any instar among larvae treated with SeMNPV + Tinopal LPW and those treated with SeMNPV alone. Larval development in SeMNPV + Tinopal LPW treated larvae was retarded, in second and fourth instars, compared with controls or larvae treated with SeMNPV alone. The OB yields from SeMNPV treated larvae were almost 1.6-fold greater in second instars (9.3 x 10(6) OBs/larvae), and 1.9-fold greater in fourth instars (1.9 x 10(8) OBs/larvae), than those obtained in larvae treated with SeMNPV + Tinopal LPW. The addition of 1% Tinopal LPW to the virus suspension did not alter the genotypic composition of viral progeny during four successive passages of the virus.     

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.     

Development and feeding efficiency of Malacosoma neustrium larvae reared with Quercus spp. leaves

Observations on larval development of Malacosoma neustrium were conducted both in a cork oak stand and in the laboratory by using leaves of different host trees (cork oak, holm oak and downy oak) as food source. Instars were determined using head capsule and frass measurements. In the field the larvae progressed up to the fifth instar before pupating, and the increase in head capsule width followed Dyars Rule with a rate of increase (R.I.) value of 1.74. The same number of instars was determined for the larvae reared with cork oak (R.I. = 1.73) and holm oak (R.I. = 1.70) leaves. The caterpillars reared with downy oak foliage completed larval development in five, six and seven instars and the R.I. values obtained were 1.60, 1.52 and 1.44 respectively. A lower mortality was recorded for the larvae reared on holm oak. Growth and feeding indices were determined for the larvae from the third up to the last instar. The highest leaf consumption was detected for the fifth instar larvae reared on holm oak. For the caterpillars which completed five instars before pupating, the relative consumption rate (RCR) decreased from the third up to the fifth instar: from 4.8 to 1.7 (cork oak), from 7.4 to 3.3 (holm oak) and from 14.3 to 2.1 (downy oak). The relative growth rate (RGR) was highest during the fourth stadium (0.24, 0.27 and 0.33 for larvae reared with cork oak, holm oak and downy oak leaves respectively) and decreased in the fifth instar (0.09, 0.14 and 0.14 for larvae reared with cork oak, holm oak and downy oak leaves respectively), probably because of greater expense of energy due to the approach of maturity. Feeding and growth indices could be useful to define a defoliation prediction model.     

Temperature and food quality effects on growth,consumption and post-ingestive utilization efficiencies of the forest tent caterpillar Malacosoma disstria (Lepidoptera: Lasiocampidae)

Temperature and food quality can both influence growth rates, consumption rates, utilization efficiencies and developmental time of herbivorous insects. Gravimetric analyses were conducted during two consecutive years to assess the effects of temperature and food quality on fourth instar larvae of the forest tent caterpillar Malacosoma disstria Hübner. Larvae were reared in the laboratory at three different temperatures (18, 24 and 30 degrees C) and on two types of diet; leaves of sugar maple trees Acer saccharum Marsh. located at the forest edge (sun-exposed leaves) or within the forest interior (shade-exposed leaves). In general, larvae reared at 18 degrees C had lower growth rates and lower consumption rates than larvae reared at the warmer temperatures (24 and 30 degrees C). Moreover, the duration of the instar decreased significantly with increasing temperatures. Type of diet also affected the growth rates and amount of food ingested by larvae but did not affect the duration of the instar. Larvae fed sun-exposed leaves consumed more food and gained higher biomasses. Values of approximate digestibility and efficiency of conversion of ingested food were also higher when larvae were fed sun-exposed leaves. Higher growth rates with increasing temperatures were primarily the result of the shorter stadium duration. The higher growth rates of larvae fed sun-exposed leaves were possibly the result of stimulatory feeding and consequently greater food intake and also a more efficient use of food ingested. This study suggests that the performance of M. disstria caterpillars could be enhanced by warmer temperatures and higher leaf quality.     

Nutrient utilization by caterpillars of the generalist beet armyworm, Spodoptera exigua

Abstract.  Beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), caterpillars are destructive crop pests responsible for considerable annual economic losses. These generalist herbivores are challenged with a diversity of dietary choices that can impact their survival, development and fecundity. In the present study, dietary choices of S. exigua caterpillars, based on the protein to digestible carbohydrate (P : C) ratio of the food, and the impact of nutritionally unbalanced foods on caterpillar performance are assessed. In choice experiments, individual third-instar caterpillars are offered simultaneously a P-biased and a C-biased food until pupation. Caterpillars feed nonrandomly and select a slightly P-biased diet (22P : 20C). In no-choice experiments, second instar caterpillars are reared until pupation on diets ranging in P : C ratio from extremely P- to extremely C-biased. High mortality and delayed development are observed on the C-rich, P-poor diets, highlighting the potential deleterious effects of excess carbohydrates and the importance of protein for growth and development. Diet-dependent differences in pupal weight or pupal lipid reserves are not observed. This contrasts with closely-related Spodoptera species where pupal mass and lipid stores increase on C-rich, P-poor diets. On the extremely P-biased diet, performance is similar to that of individuals reared on the self-selected diet, suggesting that these caterpillars may efficiently be deaminating excess amino acids to generate carbon skeletons, which are shunted into lipid biosynthesis. Spodoptera exigua caterpillars exhibit flexible and efficient pre-ingestive nutrient intake regulation and post-ingestive utilization, allowing these generalist feeders to cope with the heterogeneous diets they may encounter.     

Leaf toughness changes the effectiveness of larval aggregation in the butterfly Byasa alcinous bradanus (Lepidoptera: Papilionidae)

Two subspecies of the papilionid butterfly Byasa alcinous , B. a. bradanus and B. a. alcinous , have varying degrees of larval aggregation. Early instar larvae of ssp. bradanus always occur in aggregations. To determine the functions of larval aggregation in this subspecies, we examined the effects of leaf toughness on larval performance when caterpillars were reared alone and in aggregations. Newly hatched larvae were reared either individually or in groups of 10 and were fed either tough or tender leaves of Aristolochia debilis . When fed tough leaves, more gregarious larvae survived the first instar. This difference between solitary and aggregated larvae did not occur when caterpillars were fed soft leaves. The effects of aggregation on larval weight and duration were not significant between leaf-toughness treatments. Larval aggregation of B. a. bradanus improves larval survivorship in early instars that use host plants with tough leaves.     

Phenology of nutritional differences between new and mature leaves and its effect on caterpillar growth

Abstract. 1. We determined the phenology of the shrub Spiraea latifolia Ait. Bork. (Rosaceae), which has indeterminate shoot growth, and the effects of phenological changes in leaf quality on growth rate of the early-spring feeding buckmoth caterpillars, Hemileuca lucina Hy. Edw. (Saturniidae).
2. Leaves, regardless of whether they were newly expanded or several weeks old, were tougher later in the growth season (mid-June) than similarly aged leaves collected earlier; correspondingly, water and nitrogen content for leaves of all ages declined through the larval period. By July, newly expanded leaves had no more nitrogen than mature leaves.
3. Relative growth rate of third instar larvae fed new leaves or a mixture of new and mature leaves in early June was higher than that of those fed mature leaves, and efficiency of conversion of digested food to biomass was higher for larvae fed new leaves than for those fed mature leaves or a mixture.
4. In another experiment, larvae were reared on new leaves through the fourth instar and then fed a diet of new, mature or a combination of new and mature leaves, a regimen that was similar to the phenologies of both plants and caterpillars in the field. There was no difference in time to pupation or pupal weights among these treatments.     

The causes of colour and colour change in caterpillars of the poplar and eyed hawkmoths (Laothoe populi and Smerinthus ocellata)

Caterpillars of the poplar and eyed hawkmoths (Laothoe populi and Smerinthus ocellata respectively) were reared under different conditions in order to determine why final instar caterpillars vary in colour. Poplar hawkmoth caterpillars normally rest on the undersides of leaves. Dull green and redspotted caterpillars are genetically determined polymorphisms. Caterpillars that are not dull green, however, can become white when fed on Populus alba or yellow-green when fed on Salix fragilis. Experiments showed that it is the reflective qualities of the leaves that determines which colour the caterpillar develops: if the young larva sees white then it becomes white, but if it sees green, grey or black then it becomes yellow-green. Young eyed hawkmoth larvae always developed into grey-green final instar caterpillars under our rather poorly-illuminated rearing conditions, but when reared on wild plants in white muslin sleeves they became whitish-green. In this species also it appears that colour of the final instar is determined by the reflectance of the substrate perceived by the young caterpillar.     

The lethal plant defense paradox remains: inducible host-plant aristolochic acids and the growth and defense of the pipevine swallowtail

Toxic plants with sequestering specialists are presented with a problem because plant derived toxins protect herbivores against natural enemies. It has been suggested that early induction of toxins and later relaxation of these defenses may help the plant resolve this problem because neonate caterpillars incur the physiological cost of dealing with toxins in early life, but are denied toxins when they are able to sequester them efficiently. In California, the pipevine swallowtail, Battus philenor L. (Lepidoptera: Papilionidae), feed exclusively on Aristolochia californica Torrey (Aristolochiaceae), an endemic vine that contains toxic alkaloids called aristolochic acids that caterpillars sequester to provide chemical defense in immature and adult stages. In a field experiment, the concentration of aristolochic acids doubled in the plant following leaf damage and returned to constitutive levels after six days. Neonate pipevine swallowtail caterpillars showed no aversion to high levels of aristolochic acid in a preference test. Caterpillars reared on leaves with supplemented aristolochic acid showed no physiological cost or increased mortality compared to caterpillars reared on un-supplemented leaves. Searching efficiency and capture rate of lacewing larvae (Chrysoperla), a common predator of first instar caterpillars, was compromised significantly after feeding on caterpillars reared on leaves with supplemented concentrations of aristolochic acid compared to caterpillars feeding on control plants. Additionally, mortality of lacewings increased when they were provided with a diet of B. philenor caterpillars reared on supplemented leaves compared to caterpillars reared on control leaves. Thus, the induction of aristolochic acids in the plant following leaf damage does not resolve the problem confronted by the plant and may confer benefits to this sequestering specialist.     

Susceptibility of Spodoptera littoralis caterpillars to entomopathogenic nematode Steinernema feltiae after consumption of non-specific transgenic plants

Spodoptera littoralis caterpillars were transferred from an artificial diet to potato leaves at the start of the third or fifth instar and exposed to the infective juveniles of the nematode Steinernema feltiae since the beginning of the sixth instar until the start of pupation. Leaves were taken from the control potatoes or from genetically modified potatoes expressing either Cry3Aa toxin of Bacillus thuringiensis (Bt) or Galanthus nivalis agglutinin (GNA) which are mainly non-specific to S. littoralis larvae. The nematodes killed all the caterpillars within seven days compared with the starved larvae in the same period of exposure. The average time to death and the number of nematodes successfully invaded the larvae were affected by the period of feeding on potato leaves. In the non-starved caterpillars, which received potato leaves throughout the whole period of exposure to the nematodes, the type of potato leaves had no effect on the number of nematodes inside cadavers (p = 0.352 and F = 1.070) and also on the effect on the length of survival after exposure to the nematodes (p = 0.7892 and F = 0.596). No hazardous effect on the development and survival of entomopathogenic nematode S. feltiae which successfully invaded larvae fed on modified potato (Bt or GNA) was reported.     

Biochemical ecology of the forest tent caterpillar: responses to dietary protein and phenolic glycosides

Summary Interactions between quaking aspen (Populus tremuloides) and the forest tent caterpillar (Malacosoma disstria) are likely to be influenced by leaf protein and phenolic glycoside levels, and insect detoxication activity. We investigated the direct and interactive effects of dietary protein and phenolic glycosides on larval performance and midgut enzyme activity of forest tent caterpillars. We conducted bioassays with six artificial diets, using both first and fourth stadium larvae. Four of the diets comprised a 2×2 factorial design-two levels of protein, each with and without phenolic glycosides. Additionally, we assayed high protein diets containing S,S,S-tributylphosphorotrithioate (DEF, an esterase inhibitor) and DEF plus phenolic glycosides. Enzyme solutions were prepared from midguts of sixth instars and assayed for -glucosidase, esterase and glutathione transferase activities. First instar mortality and development times were higher for larvae on diets low in protein or containing phenolic glycosides. Effects of phenolic glycosides were especially pronounced at low protein levels and when administered with DEF. Fourth instar development times were prolonged, and growth rates reduced, in response to consumption of low protein diets. Effects of phenolic glycosides on growth were less pronounced, although the effect for larvae on the low protein diet was nearly significant. Activity of each of the enzyme systems was reduced in larvae reared on low protein diets, and esterase activity was induced in larvae fed phenolic glycosides. Our results suggest that larval performance may be strongly affected by levels of protein and phenolic glycosides commonly occurring in aspen foliage, and that these factors may play a role in differential defoliation of aspen by forest tent caterpillars.     

Experience-based behavioral and chemosensory changes in the generalist insect herbivore Helicoverpa armigera exposed to two deterrent plant chemicals

Behavioral and electrophysiological responses of larvae of the polyphagous moth species Helicoverpa armigera to two plant-derived allelochemicals were studied, both in larvae that had been reared on a diet devoid of these compounds and in larvae previously exposed to these compounds. In dual-choice cotton leaf disk and pepper fruit disk arena assays, caterpillars reared on a normal artificial diet were strongly deterred by strychnine and strophanthin-K. However, caterpillars reared on an artificial diet containing strychnine were insensitive to strychnine and strophanthin-K. Similarly, caterpillars reared on an artificial diet containing strophanthin-K were also desensitized to both deterrent chemicals. Electrophysiological tests revealed that the deterrent-sensitive neurons in taste sensilla on the maxillae of caterpillars reared on each deterrent-containing diet displayed reduced sensitivity to the two chemicals compared with the caterpillars reared on normal diets. We conclude that the experience-dependent behavioral plasticity was partly based on the reduced sensitivity of taste receptor neurons and that the desensitization of taste receptor neurons contributed to the cross-habituation to the two chemicals.     

A granulosis virus,possible biological agent for control of Adoxophyes orana (Lepidoptera: Tortricidae) in apple orchards: I. Mass production

Young larvae of Adoxophyes orana (apple race) were infected with a granulosis virus by feeding them artificial diet containing the virus suspension. The susceptibility decreased remarkably after the fourth to fifth instar. Infected larvae survived the end of the fifth (last) instar, even when they were infected at an early developmental stage. Inoculation of egg masses by dipping them into a virus suspension gave a high percentage of infection when larvae were reared en masse.     

The effect of prey size and prey density on the functional response,survival, growth and development of a predatory pentatomid bug,Podisus maculiventris say

Two experiments on the nymphal predation of Podisus maculiventris were conducted using Spodoptera litura larvae as prey. First experiment: The predator nymphs divided into three groups were reared individually from second instar to adult in a small vessel. Each nymph in the groups 1, 2 and 3 was allowed to attack the serially growing larvae (these were supplied at the rate of one per day) from 3-, 5- and 7-day old after hatching, respectively. The first prey used for the group 1 was so small that it was not only insufficient to satiate the predator but also was difficult to be searched out. But these disadvantages were soon recuperated due to the rapid growth of the prey and all nymphs could survive to adults. The survival rate of third and fourth instar nymphs in the group 3 was severely affected by vigorous counterattack of older prey larvae. Second experiment: The predator nymphs were individually reared either in a small vessel or in a large one at various rates of food supply (the prey larvae of 7-day old were used). The functional response curves obtained for each instar of the predator took a saturation type within a certain range of the prey density. The saturation level specific to each instar was generally higher for the predator reared in the large vessel than in the small one. The functional response of fourth and fifth instar nymphs was accelerated at a high prey density, viz. 16 larvae per vessel. Even at the low rate of food supply, viz. one larva per day per predator, the predator nymphs could survive to adults, but the size of resultant adults were abnormally small.     

A new cell line (NTU-SE) from pupal tissues of the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is highly susceptible to S. exigua multiple nucleopolyhedrovirus (SeMNPV) and Autographa californica MNPV (AcMNPV)

A new continuous cell line, NTU-SE, was established from the pupal tissues of an economically important pest, the beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae). This cell line contains four major morphologic types: round, polymorphic, spindle-shaped, and comma-shaped cells. The population doubling time of this new line in TNM-FH medium supplemented with 8% fetal bovine serum (FBS) at 28°C is 35.5h. The chromosomal spread from NTU-SE cells is typical to the chromosomal morphology of lepidopteran cell lines. Confidently, NTU-SE cell line is a new cell line that exhibits distinct isozyme patterns of esterase, lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) from those of the other insect cell lines. In addition, the DNA sequence of the nuclear ribosomal internal transcribed spacer (ITS) region of NTU-SE cells is above 96% identical to that sequence of S. exigua larvae, as compared to only 66% identical to that of S. litura larvae. The NTU-SE cell line is highly susceptible to S. exigua multiple nucleopolyhedrovirus (SeMNPV) and Autographa californica MNPV (AcMNPV). Therefore, a highly virulent SeMNPV strain, SeMNPV-1, had been successfully isolated and propagated in NTU-SE cells. We conclude that the NTU-SE cell line will be a useful tool for the selection and mass production of highly virulent SeMNPV strains for the S. exigua biocontrol and the baculovirus based recombinant protein expression systems.     

Patterns and mechanisms of growth of fifth-instar Manduca sexta caterpillars following exposure to low- or high-protein food during early instars.

For many insect herbivores, variation in protein availability is a pervasive part of the environment. I explore how variable protein availability affects growth rates of fifth-instar Manduca sexta caterpillars and how growth is related to behavior and physiology. Groups of larvae were reared on low- or high-protein artificial diets (5.9% and 17.7% casein by dry weight, respectively) and then transferred in the fifth instar to the same or opposite diet. During or after the 24-h period following transfer, I measured growth rate, consumption rate, growth efficiency, midgut proteolytic activity, and masses of midgut contents and tissues. Fifth-instar caterpillars reared in earlier instars on high-protein diet grew about 20% more rapidly over 24 h than did caterpillars reared on low-protein diet. This growth pattern appears to be caused by differences in consumption and growth efficiency: caterpillars reared on high protein consumed more food, and used it more efficiently, than did caterpillars reared on low-protein diet. Over the short term (24 h), in contrast, fifth instars that received low-protein diet grew as rapidly as caterpillars that received high-protein diet. Increased (compensatory) consumption appears to be the primary mechanism by which caterpillars consuming low-protein food maintained growth rates.     

Direct and indirect effects of predatory wasps (Polistes sp.: Vespidae) on gregarious caterpillars (Hemileuca lucina: Saturniidae)

Summary We examined how predation by vespid wasps,Polistes dominulus andP. fuscatus, affected the behavior, growth rate and survivorship of aggregated caterpillars ofHemileuca lucina (Saturniidae). Although these larvae can exhibit a variety of defense and escape behaviors, in general larvae reacted to wasp attacks by clinging to the hostplant. Neighboring larvae in the aggregation responded by leaving the feeding site and moving to the interior or base of the plant. To determine wheter wasp attack affected the behavior and growth of the caterpillars that escaped, a field experiment was conducted with treatments of: 1) larvae exposed to wasps, 2) larvae protected from wasps, and 3) larvae protected from wasps but with the attack of wasps simulated (=harassment). Over just one instar, protected larvae gained significantly more weight than the harassed larvae, which in turn weighed significantly more than the larvae that escaped the wasps. The behavior of attacked and harassed larvae differed from that of the protected larvae; the disturbed larvae often fed in smaller groups and in shaded portions of the plant where only mature leaves were available. A laboratory experiment showed that at 35° C (daytime temperature) larvae had significantly higher relative growth rates and significantly shorter instar duration than larvae reared at 25° C. Our results suggest that wasps, in addition to killing caterpillars, indirectly affect larval fitness by slowing larval growth, at least in part by forcing larvae into cooler microhabitats where leaves are of lower quality.     

Rearing the 28-spotted ladybird beetle,Henosepilachna vigintioctopunctata (Coleoptera: Coccinelidae), with a switchover from host plant leaves to artificial diet

In this study, I tested an artificial diet, Insecta LFS, for rearing the 28-spotted ladybird beetle, Henosepilachna vigintioctopunctata (Fabricius). H. vigintioctopunctata larvae could not be reared through all of the larval stages on the artificial diet. However, initially they could be reared on tomato leaves up to the second or third instar, and thereafter exclusively on the artificial diet. The larval and pupal periods were not significantly different from those reared only on tomato leaves. For females reared by the diet-switching method, the preoviposition period was significantly longer and the number of eggs laid significantly lower than for those on tomato leaves. However, these differences did not become a hindrance to laboratory rearing. This rearing method saves labor involving obtaining fresh plant leaves and produces a reliable supply of the insects.