Stem-boring Diptera in perennial ryegrass in relation to fertiliser. I. Nitrogen level and form

The effects of applying nitrogen to a perennial ryegrass sward were studied in relation to the size and nature of populations of dipterous stem-bores. Two levels of both ammonium sulphate and calcium nitrate were applied to the sward. Larvae were more numerous in the plots treated with high levels of nitrogen regardless of the form applied. Also, there were more larvae in the plots treated with ammonium sulphate than in those treated with calcium nitrate. A limited range of stem-borer species predominated. These were Oscinella vastator, two forms of O. frit and Geomyza tripunctata. Stem-borer species were distributed differently between plots receiving high and low nitrogen levels; G. tripunctata occurred almost exclusively on plots receiving high nitrogen applications while O. vastator was more frequent in those receiving low levels of nitrogen.     

Patterns of infestation by stem-borers (Chloropidae and Opomyzidae) in grassland

The colonisation of a newly sown field of perennial ryegrass (Lolium perenne L.) by stem-boring dipterans was studied. Overall there were significantly more stem-borer larvae close to the edge of the field (within 15 m) than in the middle. Oscinella vastator Curtis and to a lesser extent O. frit L. (aberrant form) mainly colonised the edge of the field while O. frit and Geomyza tripunctata Fallén colonised the whole field more evenly. The results have implications for control strategies of the stem-borer complex.

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Résumé L'étude porte sur la colonisation d'une prairie nouvellement semée en ray-gras anglais (L. perenne) par des diptères Chloropidae et Opomyzidae. La proportion de talles contenant des larves atteignait 10% en octobre, mais avait diminué à la fin de novembre. Il y avait significativement plus de larves près de la périphérie du champ (jusqu'à 15 m de la bordure) qu'au centre. La densité des larves semble être influencée par la nature des cultures avoisinantes. Oscinella vastator et, dans une moindre mesure, O. frit (forme aberrante) colonisant principalement les bordures du champ, ce qui indique une migration principalement locale. O. frit et Geomyza tripunctata sont répartis d'une façon plus uniforme dans le champ, peut-être parce que ces espèces sont plus migratices. Ces résultats ont une influence dans la mise au point d'un système de protection contre ces espèces.

     

Estuarine gradients and the growth and development of Agapanthia villosoviridescens, (Coleoptera), a stem-borer of the salt marsh halophyte Aster tripolium

Summary Phytophagous insects of estuarine salt marshes which live inside their host plants are not directly exposed to estuarine gradients. Host plant quality, however, may change along the estuary as a result of the direct effects of these gradients; as a consequence growth and development of endophagous insects may be influenced. The results of a study of the life cycle of Agapanthia villosoviridescens (Coleoptera, Cerambycidae), a stem-borer of the halophyte Aster tripolium, on three salt marshes along the Westerschelde estuary (the Netherlands) are in line with this hypothesis. It was shown that in upstream direction (1) mean larval weights were consistently higher during the entire period of larval development; (2) the percentage of late instars on a given sampling date generally was higher; (3) the percentage of larvae which underwent successful metamorphosis increased. Furthermore, (4) dry weight of the imagos was highest on the least saline marsh. The effects of estuarine gradients on the Aster host plants was indicated by differences in growth and chloride content between the populations of the three marshes. The non-overlapping geographic distribution of Agapanthia villosoviridescens and its host plant Aster tripolium on the Westerschelde salt marshes may be related to the effects of estuarine gradients on the suitability of the host plant.     

The performance of the leaf mining microlepidopteran Bucculatrix maritima (Stt.) on the salt marsh halophyte,Aster tripolium (L.), exposed to different salinity conditions

Summary The performance of phytophagous insects is influenced by the nutritional quality of the food plant, which may vary with environmental conditions. Hardly any information exists on food-plant mediated effects of variable soil salinity on the performance of phytophagous insects. Conspicuous differences in salinity levels, however, are found in soils of intertidal wetlands such as salt marshes and mangroves. The growth of larvae of Bucculatrix maritima, a leaf miner of the salt marsh halophyte Aster tripolium, was studied on the host plant along the salinity gradient of the Westerschelde estuary (S.W. Netherlands). In addition, its performance on A. tripolium grown on low or high salinity culture medium was investigated experimentally. Although salinity conditions significantly influenced the chemistry of the host plants, insect performance seemed almost unaffected, although near the mouth of the estuary high environmental salinities may have caused some inhibition of larval growth. The results contrast with our previous studies on the stem-borer Agapanthia villosoviridescens, which showed that growth and development was conspicuously influenced by the changing characteristics of Aster tripolium along the estuarine salinity gradient. The location-dependent qualities of halophytes in an estuary thus appear to have species-specific effects on insect performance. We hypothesize that this phenomenon contributes to the existence of non-identical distribution patterns of phytophagous insects associated with the same halophyte in an estuary.     

Abundances of five parasitoids attacking the scale insect <Emphasis Type="Italic">Nipponaclerda biwakoensis</Emphasis> on morphologically changed reed shoots due to damage by a stem-boring caterpillar

Abundances of the scale insect Nipponaclerda biwakoensis and its five parasitoids per shoot of the common reed, Phragmites australis, were compared between shoots damaged by a stem-boring caterpillar and undamaged shoots. Reed shoots that were damaged by the stem-borer in spring change morphologically during summer, inducing tillers from the nodes beneath the damaged part. The number of female scales per shoot did not differ significantly between damaged and undamaged shoots in the second scale generation (September), but was significantly lower on damaged shoots in the third generation (November). Three parasitoid species attacking the scale exhibited different responses to the shoot damage, with the response by each parasitoid being constant in the two scale generations: the parasitism rate by Aprostocetus sp. per shoot was higher on damaged shoots, whereas that by Astymachus japonicus was lower on damaged shoots, and no difference was detected for Boucekiella depressa. In the third scale generation, the parasitism rate by Encyrtidae sp. 1 showed no difference, with respect to shoot damage, whereas that by Encyrtidae sp. 2 was lower on damaged shoots. In three dominant parasitoids, shoot damage had no effect on the number of emerging adults per host, and the sex ratio and body size of the adults. The number of emerging adults per shoot differed significantly between damaged and undamaged shoots for four parasitoids, except B. depressa. These results suggest that shoot damage by the stem-borer exerts a delayed negative impact on the scale numbers and affects the parasitism rate of the scales by three parasitoids and the emerging adult numbers of four parasitoids.     

咖啡旋皮天牛幼虫蛀道及蛀道行为的空间特征分析(英文)

研究了咖啡旋皮天牛Acaloleptacervinus (Hope)韧皮部蛀道和木质部蛀道的空间特征 ,揭示了其幼虫的蛀道行为特性。结果显示 ,钻蛀孔集中分布于咖啡树径 4cm处 ,当钻蛀孔处树径大于 4cm时 ,木质部蛀道大多向上发展 ,当小于 4cm时则向下发展 ;钻蛀孔在树干上的垂直分布则显示钻蛀孔多分布于靠近树干基部的区域 ;钻蛀孔多紧临树干上的凸起物旁 ,如侧枝基部、瘤凸旁等 ;较多数的钻蛀孔位于树干的南面。以上结果说明咖啡旋皮天牛幼虫的钻蛀行为具有很强的位置选择性。这一研究有助于我们进一步理解咖啡旋皮天牛幼虫的钻蛀行为 ,进而找到具有针对性的防治措施。     

Susceptibility of Eldana saccharina (Lepidoptera: Pyralidae), Busseola fusca and Sesamia calamistis (Lepidoptera: Noctuidae) to Bacillus thuringiensis Cry toxins and potential side effects on the larval parasitoid Cotesia sesamiae (Hymenoptera: Braconidae)

Laboratory trials were conducted to determine the efficacy of four Bacillus thuringiensis (Bt) Cry toxins at five different concentrations (0.016, 0.08, 0.4, 2, 10 μg/mL) for controlling three lepidopteran stem-borer species (i.e., the pyralid Eldana saccharina and the noctuids Busseola fusca and Sesamia calamistis) as well as to evaluate their indirect effect on the braconid larval parasitoid Cotesia sesamiae. In addition, larvae from the treatments above, after having been parasitized, were either fed a contaminated (group 1) or a toxin-free (group 2) diet and compared with a control (i.e., parasitized larvae which have never fed on Bt-toxin). All Bt Cry toxins induced larval feeding inhibition. Compared with the control, significant mortality resulted at all concentrations and for all species of Lepidoptera. Cry1Ab was the most toxic with 10 days post treatment mortalities ranging from 81% in B. fusca and S. calamistis to 100% in E. saccharina. In contrast, Cry1Ac had comparatively low toxicity particularly for B. fusca and S. calamistis (e.g., respectively, 54 and 74% mortality at 10 days at the highest concentration). In the toxin-treated group 1, percentages of C. sesamiae cocoon-producing moth larvae were higher compared to group 2 and the control, whereas clutch size was higher than in group 2 but similar to the control. In both groups, 0.016, 0.08 μg/mL CrylAc yielded lower female-biased sex ratios than the control. It was suggested that paralyses of the moth larvae caused by the toxin may have facilitated parasitization leading to higher parasitism and clutch size.     

Factors affecting parasitism of stem-borer larvae in Italian ryegrass (Lolium multiflorum)

Factors affecting parasitism of stem-boring larvae which attack Italian ryegrass were studied. Stem-boring larvae dissected out of tillers from a range of Italian ryegrass cultivars showed parasitism of between 10–65%. However, the level of attack by Chasmodon apterus Nees, a ground-dwelling braconid which dominated the parasitoid complex, did appear to be affected by the plant cultivar, independently of the level of stem-borer infestation.Italian ryegrass cultivars, newly-sown on land previously sown to barley and which had received conventional seed-bed cultivations showed low levels of attack by C. apterus, but increased levels of attack by Halticoptera circulus Walker. The use of the pesticide phorate adversely affected parasitism by c. apterus.

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Résumé L'étude porte sur les facteurs influençant le parasitisme par des hyménoptères des larves mineuses des tiges du ray-gras Italien. Le niveau du parasitisme dans les larves extraites des talles de 13 cultivars différents du ray-gras Italien est identique. Toutefois, le niveau d'attaque par Chasmodon apterus, majoritaire dans le complexe des parasites, semble être affecté par le cultivar, quel que soit le niveau d'infestation par les mineuses des tiges. Les effectifs des larves de mineuses des tiges et de C. apterus semblent augmenter parallèlement, le maximum étant atteint avec le cultivar Tiara. Bien que la densité des mineuses soit plus importante pour d'autres cultivars, le niveau de parasitisme y est moindre. Les cultivars de ray-gras Italiens semées après une culture d'orge, et recevant une fertilisation conventionnelle au semis, sont peu attaqués par C. apterus, probablement parce que ce parasite colonise les champs lentement; par contre le niveau d'attaque dû à Halticoptera circulus est accru. Les traitements pesticides à base de phorate affectent négativement le parasitisme par C. apterus.

     

Endophytic Colonisation of Opium Poppy, Papaver somniferum, by an Entomopathogenic Beauveria bassiana Strain

Beauveria bassiana strain EABb 04/01-Tip isolated from stem-borer larvae of Timaspis papaveris (Hymenoptera: Cynipidae), a serious pest of opium poppy in Spain, was shown to be able to become established endophytically in this pharmaceutical crop. Microbiological, molecular and light and electron microscopic methods were used to study fungal colonisation and to describe its mode of penetration. After inoculation with a foliar spray of conidia, microbiological methods showed 100% of plants examined 24, 48, 72 and 144 h after treatment to be colonised endophytically by the fungus, although the percentage of previously surface sterilised leaf pieces showing fungal growth was 100% at 24 and 48 h, and 80 and 75% at 72 and 144 h after treatment, respectively. The fungus was also observed in leaf pieces obtained from newly formed leaves, indicating that it could spread from treated leaves to leaves formed after fungal application. For molecular studies, a polymerase chain reaction (PCR) protocol was used to amplify the ITS1-5.8S-ITS2 regions of the rDNA of the plant and the fungus. This procedure allowed the detection of the fungus on the surface of the leaves and also endophytically, but only at 72 h after treatment. A nucleotide BLAST search revealed that the ITS1-5.8S-ITS2 sequence of strain EABb 04/01-Tip showed 100% homology with a similar sequence from Cordyceps bassiana. SEM images revealed that although numerous conidia were observed on the leaf surface, few germinated and penetrated. Intracellular colonisation by B. bassiana was not observed, but hyphae were detected growing into the xylem vessels. The fungus was found to colonise 40.5 ± 4.3% of seedlings (with two cotyledons and the two first real leaves) from seeds dressed with a fungal spore suspension. These results may have implications in the biological control of T. papaveris, including the possible systemic protection of the plant against this cynipid.     

Influence of toxic and non-toxic phytoplankton on feeding and survival of Dreissena polymorpha (Pallas) larvae

Grazing and survival of larvae of the zebra mussel, Dreissena polymorpha, on a green alga and cyanobacteria were studied in laboratory experiments. Clearance rates of the larvae were determined for Chlamydomonas reinhardtii (green alga), two non-toxic and two toxic Microcystis aeruginosa strains (Cyanobacteria). Clearance rates of larvae on non-toxic Microcystis were significantly higher than on toxic Microcystis. The clearance rate on Chlamydomonas reinhardtii was in between the clearance rates on toxic and non-toxic Microcystis strains and not significantly different from them. Effects of toxicity of Microcystis on the survival of zebra mussel larvae was investigated in a short-term experiment. Survival of larvae fed toxic Microcystis was lower than that of larvae fed non-toxic Microcystis, but higher than that of starved larvae. This may imply that, for survival of zebra mussel larvae, it is better to have bad quality (toxic) food than no food.     

Functional response of Chrysoperla carnea (Neuroptera: Chrysopidae) to Helicoverpa armigera (Lepidoptera: Noctuidae): Effect of prey and predator stages

Abstract Understanding predator–prey interactions has a pivotal role in biological control programs. This study evaluated the functional response of three larval instars of the green lacewing, Chrysoperla carnea (Stephens), preying upon eggs and first instar larvae of the cotton bollworm, Helicoverpa armigera Hübner. The first and second instar larvae of C. carnea exhibited type II functional responses against both prey stages. However, the third instar larvae of C. carnea showed a type II functional response to the first instar larvae of H. armigera, but a type III functional response to the eggs. For the first instar larvae of C. carnea, the attack rate on H. armigera eggs was significantly higher than that on the larvae, whereas the attack rate of the second instar C. carnea on H. armigera larvae was significantly higher than that on the eggs. For the third instar larvae of C. carnea, the attack rate on the larvae was 1.015 ± 0.278/h, and the attack coefficient on the eggs was 0.036 ± 0.005. The handling times of the third instar larvae on larvae and eggs were 0.087 ± 0.009 and 0.071 ± 0.001 h, respectively. The highest predation rate was found for the third instar larvae of C. carnea on H. armigera eggs. Results of this study revealed that the larvae of C. carnea, especially the third instar, had a good predation potential in controlling H. armigera eggs and larvae. However, for a comprehensive estimation of the bio‐control abilities of C. carnea toward H. armigera, further field‐based studies are needed.     

Susceptibility of Meligethes spp. and Dasyneura brassicae to entomopathogenic nematodes during pupation in soil

The susceptibility of pupating larvae of pollen beetles, Meligethes spp. Stephens (Coleoptera: Nitidulidae) and brassica pod midges, Dasyneura brassicae Winnertz (Diptera: Cecidomyidae) to entomopathogenic nematodes (Nematoda: Rhabditida) was studied in the laboratory. The results showed that brassica pod midge larvae were almost unaffected by the tested nematodes (Steinernema bicornutum, S. feltiae and Heterorhabditis bacteriophora) whereas successful pupation of pollen beetle larvae was reduced with increasing number of nematodes (S. bicornutum, S. carpocapsae, S. feltiae and H. bacteriophora). The exposed larvae had been collected in the field and some of the pollen beetle larvae were parasitised by parasitoid wasps. It appeared that parasitised larvae were less affected by nematodes than non-parasitised larvae.     

Larval interactions in aphidophagous predators: effectiveness of wax cover as defence shield of Scymnus larvae against predation from syrphids

Small-sized predators in the aphidophagous guild of Aphis gossypii Glover colonies on hibiscus trees in Japan exploit aphids at low prey abundance. Scymnus (Pullus) posticalis Sicard beetles were the first predatory species to attack aphids in the spring, and their larvae co-occurred with larvae of Eupeodes freguens (Matsumura) syrphids in aphid-infested leaves of hibiscus for 3 weeks in absence of large-sized coccinellid predators. Larval interaction between Scymnus and syrphid predators was examined in relation to effectiveness of wax cover of Scymnus against predation from syrphids. Waxless first instar larvae were not protected but wax-covered larvae of second, third and fourth instars were protected from predation by syrphid larvae. The protection was lower in the second instar which has a thin wax cover and significantly higher in the third and fourth instars having a thick wax cover. In addition, larvae from which the wax was removed were significantly more vulnerable to predation. Vulnerability of Scymnus larvae to predation from syrphids was directly related to the thickness of wax cover. Results suggest that the wax cover of Scymnus larvae act as an effective defence mechanism against predation from syrphid larvae.     

油茶新害虫南方锦天牛形态特征和生物学特性研究(英文)

南方锦天牛Acalolepta speciosa属鞘翅目天牛科沟胫天牛亚科锦天牛属昆虫,是近年在油茶Camellia oleifera上新出现的一种蛀干害虫.本文首次对该天牛的形态特征,包括雌雄生殖器结构进行了详细的描述,以期为该虫的鉴定提供可靠的依据,并首次报道了该虫生物学特性.     

Dynamic changes of gut bacterial communities present in larvae of Anoplophora glabripennies collected at different developmental stages

The Asian long-horned beetle, Anoplophora glabripennies (Motschulsky), is a destructive wood-boring pest that is capable of killing healthy trees. Gut bacteria in the larvae of the wood-boring pest is essential for the fitness of hosts. However, little is known about the structure of the intestinal microbiome of A. glabripennies during larval development. Here, we used Illumina MiSeq high-throughput sequencing technology to analyze the larval intestinal bacterial communities of A. glabripennies at the stages of newly hatched larvae, 1st instar larvae and 4th instar larvae. Significant differences were found in larval gut microbial community structure at different larvae developmental stages. Different dominant genus was detected during larval development. Acinetobacter were dominant in the newly hatched larvae, Enterobacter and Raoultella in the 1st instar larvae, and Enterococcus and Gibbsiella in the 4th instar larvae. The microbial richness in the newly hatched larvae was higher than those in the 1st and 4th instar larvae. Many important functions of the intestinal microbiome were predicted, for example, fermentation and chemoheterotrophy functions that may play an important role in insect growth and development was detected in the bacteria at all tested stages. However, some specific functions are found to be associated with different development stages. Our study provides a theoretical basis for investigating the function of the intestinal symbiosis bacteria of A. glabripennies.     

Overwintering strategy of endoparasitoids in Chilo suppressalis: a perspective from the cold hardiness of a host

Although parasitoids ultimately kill their host, koinobiont parasitoids must protect not only themselves but also their hosts against extreme environments. In this study, the parasitism rate of Chilo suppressalis Walker (Lepidoptera: Pyralidae) was investigated, and the average body weights, supercooling points, and concentrations of glycerol (acting as a cryoprotectant) in the hemolymph were compared between parasitized and non‐parasitized larvae. Five species of koinobiont endoparasitoids parasitized the overwintering C. suppressalis larvae and the total parasitism rate was 47.6% (n = 1 537). Average body weight of parasitized larvae was significantly lower than that of non‐parasitized larvae, and the parasitism rate of the lighter group (20–30 mg) was highest. The supercooling point of parasitized C. suppressalis larvae (?15.7 ± 0.3 °C) was significantly lower than that of the non‐parasitized larvae (?14.3 ± 0.2 °C). In addition, supercooling points were not correlated with body weights between parasitized and non‐parasitized larvae, indicating that cold hardiness of parasitized larvae was enhanced by endoparasitoids. Furthermore, the concentration of glycerol in the hemolymph was significantly higher in parasitized larvae (205.0 ± 7.1 μmol ml^?1) than in non‐parasitized larvae (169.8 ± 14.4 μmol ml^?1), which suggests that the mechanism that decreases the supercooling point of parasitized larvae was associated with glycerol. All these results indicated that the cold hardiness of parasitized C. suppressalis larvae was enhanced by their endoparasitoids, which benefitted overwintering endoparasitoids.     

Effects of spatio-temporal intervals between newly-hatched larvae on larval survival and development inMonochamus alternatus (Coleoptera: Cerambycidae)

The effects of distance between hatching larvae on survival and development were investigated inMonochamus alternatus. Two newly-hatched larvae were inoculated intoPinus densiflora bolts at a distance of 2.5 cm or 10 cm, simultaneously or at an interval of 2 weeks. Some larvae were inoculated singly as a control. When larvae were inoculated simultaneously, mortality of the closely-inoculated larvae was significantly higher than that of distantly-inoculated larvae. Such high mortality was identified as due to conspecific bites. When the two larvae were inoculated asynchronously, the first-inoculated larvae killed some second-inoculated larvae but were never killed by them. Consequently, mortality was higher in second-inoculated larvae than in first-inoculated larvae. In particular, there was a significant difference in mortality between them when the larvae had been inoculated closely. The mortality of second-inoculated larvae was higher in the closely-inoculated group than in the distantly-inoculated group although there was no significant difference between them. In the case of two simultaneously-inoculated larvae, the initial distance between them had no significant effect on the development and growth in the early larval stage. When the larvae were inoculated asynchronously, the first-inoculated larvae grew more quickly than singly-inoculated control larvae.     

Ecosystem engineering and manipulation of host plant tissues by the insect borer Oncideres albomarginata chamela

Ecosystem engineering by insect herbivores occurs as the result of structural modification of plants manipulated by insects. However, only few studies have evaluated the effect of these modifications on the plant responses induced by stem-borers that act as ecosystem engineers. In this study, we evaluated the responses induced by the herbivory of the twig-girdler beetle Oncideres albomarginata chamela (Cerambycidae: Lamiinae) on its host plant Spondias purpurea (Anacardiaceae), and its relationship with the ecosystem engineering process carried out by this stem-borer. Our results demonstrated that O. albomarginata chamela branch removal induced the development of lateral branches increasing the resources needed for the development of future insect generations, of its own offspring and of many other insect species. Detached branches represent habitats with high content of nitrogen and phosphorous, which eventually can be incorporated into the ecosystem, increasing nutrient cycling efficiency. Consequently, branch removal and the subsequent plant tissue regeneration induced by O. albomarginata chamela represent key mechanisms underlying the ecosystem engineering process carried out by this stem-borer, which enhances arthropod diversity in the ecosystem.     

Effect of hunger on the allocation of time among pea plants by the larvae of an aphidophagous hover fly,Eupeodes corollae [Dipt: Syrphidae]

We observed the movement of predatory larvae of the syrphid flyEupeodes corollae (F.) (formerlyMetasyrphus corollae) among small pea plants with and without aphids. Starved larvae spent longer time than well-fed larvae on similar plants and both groups of larvae stayed longer on plants with aphids than on plants without aphids. On plants with aphids, larvae which failed to capture prey left the plant sooner than those which captured aphids. The capture of at least one aphid on a plant increased the persistence of syrphid larvae. The average rate of energy gain was higher for well-fed larvae than for starved larvae because starved larvac stayed on plants even when their rate of return was lower. When larvae that had captured aphids left plants, their rate of energy gain, tended to be lower than at any time following capture of the 2^nd, aphid. The 1^st aphid was captured in less time than similar larvae spent on plants without aphids. Time between captures of aphids by well-fed larvae was less than the time such larvae spent on plants without aphids. Among starved larvae, the intercatch intervals were similar to the time on plants without aphids. We discuss the significance of these results relative to current predator foraging theory and the efficiency ofE. corollae as a biological control agent.      

Nondevelopment ofCotesia kariyai(Hymenoptera: Braconidae) in Entomopoxvirus-Infected Larvae ofPseudaletia separata(Lepidoptera: Noctuidae)

Interaction between an entomopoxvirus (PsEPV) and a gregarious braconid endoparasitoid,Cotesia kariyai,inPseudaletia separatalarvae showed that infection of larvae with PsEPV was deleterious to the development and survival ofC. kariyai.The survival and development ofC. kariyaiin PsEPV-infectedP. separatalarvae depended on the length of time between parasitization and viral infection. No parasitoid larvae emerged from PsEPV-infected hosts when host larvae were exposed simultaneously to parasitization and PsEPV inoculation whereas more than 80% of the hosts produced parasitoids when PsEPV was administered 5 days postparasitization.C. kariyailarvae in PsEPV-infected hosts showed a retarded development, shrank, and died about 8 days after viral exposure. Virion-free plasma from PsEPV-infectedP. separatalarvae was toxic to the parasitoid larvae even up to a dilution level of 32 when it was injected intrahemocoelically into the host larvae. Development of parasitoids in hosts that were simultaneously parasitized and injected with the virion-free plasm never progressed beyond the egg stage. The parasitizedP. separatalarvae injected with the virion-free plasma did not pupate and died within 30 days after injection.