In vitro rearing of Campoletis sonorensis, a larval endoparasitoid of Heliothis virescens from egg to third instar in an artificial medium devoid of insect sources

Campoletis sonorensis is a solitary larval endoparasitoid of several Heliothis spp. pests. This study was carried out to develop media devoid of insect sources for in vitro rearing the parasitoid. Trehalose, lysine, threonine, asparagine, glutamine, hydroxyproline, serine, bovine serum albumin, and lactalbumin were beneficial to C. sonorensis. Addition of fresh chicken egg yolk at a low level improved the artificial media. Addition of 20-hydroxyecdysone increased the molting rate, reduced the critical size at molt and decreased development time. Parasitoid development in vitro was dependent on eggs that had been in the host for at least 22 h. Luminosity was also critical for the development of C. sonorensis in vitro. Optimal development occurred in a L14:D10 photoperiod at 43 Lux light intensity. Utilizing the best media and conditions, 100% of the parasitoid larvae reached the second instar and over 37% molted to the third instar. However, no further development occurred.     

Interaction of a solitary larval endoparasitoid, Microplitis mediator, with its host, Mamestra brassicae: host acceptance and host suitability

Abstract:  Microplitis mediator (Haliday) (Hym., Braconidae) is an important parasitoid of early instar larvae of the European cabbage moth, Mamestra brassicae L. (Lep., Noctuidae). In the laboratory, we examined attack responses of female M. mediator to the first three larval instars of M. brassicae . Females were presented with M. brassicae larvae either one individual at a time in a no-choice experiment, or three individuals, one from each instar, simultaneously in a choice experiment. Whether or not there was choice, naïve female parasitoids attacked a high proportion of larvae and did not discriminate among instars. In the no-choice experiment, attacked larvae were reared, and parasitoid cocoons were produced from about 76% of larvae attacked as first and second instars, but from only 19% of larvae attacked as third instars. Dissections of attacked larvae from the choice experiment showed that about 79% of attacks on first and second instars resulted in oviposition compared with only 49% for third instars. When given choice, frequency and number of attacks on first instar larvae increased with increasing parasitoid experience. Our results suggest that first and second instar larvae of M. brassicae are suitable hosts for M. mediator , but that third instar larvae are suboptimal both because oviposition attempts were frequently unsuccessful and because immature parasitoids failed to complete development. Nevertheless, naïve attacking parasitoids exhibited minimal discrimination among instars, although experienced parasitoids most frequently attacked first instar larvae. The host selection behaviour of M. mediator is discussed in the context of optimal foraging theory and implications for biological control.     

Reproductive biology and small-scale rearing of cherry bark tortrix and its candidate biological control agent

Abstract:  The larval parasitoid, Campoplex dubitator (Hym.,: Ichneumonidae), is under consideration as an agent for classical biological control of cherry bark tortrix (CBT), Enarmonia formosana (Lep.,: Tortricidae), in North America. A comprehensive risk analysis of the candidate agent will require prosperous cultures of both the pest and its parasitoid. We present a rearing method for small-scale production of both species using a bean-based artificial diet, with additional information on the reproductive biology of C. dubitator . Based on estimated survivorship probabilities, a CBT egg had a 70% chance of developing completely to the adult stage under this system. The success of parasitism, however, was very dependent on the instar of the CBT host larva at the time of oviposition. All parasitised first instar larvae died shortly after the attack, rendering them unsuitable for oviposition, while 50% of parasitised second instar larvae died prematurely. In contrast, early mortality was 15–30% for larvae parasitised in the third to fifth instars. Regardless of the instar at oviposition, approximately 90% of the surviving hosts yielded parasitoids, showing a high acceptance by C. dubitator of second to fifth instars for oviposition.     

Influence of generation and photoperiod on larval development of Lobesia botrana (Lepidoptera: Tortricidae)

The influence of generation (under field conditions) and photoperiod (under laboratory conditions) on Lobesia botrana larvae development was studied. Some larvae were collected during three annual generations in two grape-growing areas of northeastern Italy, and others were individually reared in the laboratory from egg to pupa on an artificial diet under two different photoperiod conditions (respectively, daylight 16 h/d [long day {LD}] and 14 h/d [short day {SD}]). The mandible lengths of collected larvae were measured and the data analyzed morphometrically to determine the number of larval instars. In the laboratory study, the number of larval moultings, the mandible length of each instar, the development time from hatching larva to pupa, and the pupal weight were considered. The measurement of mandible lengths of larvae collected in the field indicated the existence of five larval instars in all three annual generations, but the size of the two oldest larval instars was significantly higher for third-generation larvae than for the previous generations. Under laboratory conditions, the larvae usually exhibited five instars, but the mandible lengths of larvae and the pupa size were greater for individuals reared under SD. These also took a greater number of days to develop from hatching larvae to pupae. Because a larger size of the final larval instar occurs in individuals that produce diapausing pupae under SD in both the laboratory and the field, a positive association between larval size and the probability of surviving the winter can be inferred.     

Biosteres longicaudatus: Developmental dependence on host (Anastrepha suspensa) physiology

Larvae of Anastrepha suspensa that were in the first day of the third instar were parasitized by females of the solitary endoparasitoid, Biosteres longicaudatus. At the end of the 6-hr oviposition period, larvae were ligated posterior to the ring gland so that some larvae had parasitoids anterior to the ligature while in others, the parasitoids were in the abdomen, posterior to the ligature. Ninety-two percent of the parasitoids anterior to the ligature hatched to the first through third instars. Parasitoids posterior to the ligature had a 75% egg hatch to the first instar only. No larval molts to the second or subsequent instars occurred in these parasitoids. Upon parabiosis to 3-day-old, unparasitized host pupae, the ligated larvae pupated and 97% of the first-instar parasitoids in these parabiosed larval abdomens molted to the second instar. Newly laid parasitoid eggs transplanted to 3-day-old pupal hosts had less than one-third of the egg hatch of those transplanted to first-day third-instar hosts. The data implicate the physiological state of the host (vis-a-vis pupation and associated events) as being an important factor in the development of the endoparasitoid.     

Developmental interaction between suboptimal instars of Spodoptera littoralis (Lepidoptera:Noctuidae) and its parasitoid Microplitis rufiventris (Hymenoptera:Braconidae)

Relative effects of parasitism by Microplitis rufiventris on the development of the third instar Spodoptera littoralis (preferable, optimal host) with the development of penultimate (5th) and last (6th) instars (suboptimal hosts) were investigated. Newly molted 6th instar hosts were more acceptable for parasitization by the wasp female than older hosts. In singly parasitized 3rd instar hosts, 82.0 +/- 3.9% of the parasitoid eggs developed to full-grown instar wasp larvae. However, parasitoid eggs deposited singly in 73.9 +/- 3.3% of 5th and 100% of 6th instar hosts failed to develop. Superparasitization in the 3rd instar hosts reduced the production of pseudoparasitized larvae and, conversely, all parasitized hosts yielded viable parasitoid offspring. In suboptimal hosts, the development interaction between the parasitoid and its host larvae was highly influenced by the age of hosts at parasitism, load of deposited eggs, and other parasitoid factors. The latter factors, e.g., mainly calyx fluid particles, might be involved in establishing parasitoid eggs in the suboptimal hosts. In the last two host instars, superparasitization significantly increased the number of parasitoid larvae successfully reaching their final instar. Variation in host quality, e.g., physiological status, might be attributed, in part, to the partial breakdown of the solitary habit observed in the earlier instars. More parasitoid eggs developed to mature parasitoid larvae in hosts superparasitized as 6th instar than parasitoid eggs laid in 5th instar hosts. Superparasitization significantly lengthened the developmental period of 5th and 6th host instars and inhibited their development to the pupal stage. Studying parasitoid development in suboptimal instars of its habitual host provided physiological insight, as shown here. The results may have implication for biological control and in vitro mass rearing programs with solitary parasitoids.     

The differential mortality at various life stages of the greenhouse whitefly,Trialeurodes vaporariorum (Homoptera: Aleyrodidae), by infection with the fungus Aschersonia aleyrodis (Deuteromycotina: Coelomycetes)

The parasitoid Encarsia formosa is commonly applied to control the greenhouse whitefly Trialeurodes vaporariorum in glasshouse tomatoes and cucumbers. Nevertheless, in some cases the control capacity of this natural enemy is insufficient and an additional selective pest-suppressing agent is desirable. The entomopathogenic fungus Aschersonia aleyrodis was applied to cucumber plants carrying whiteflies in different developmental stages. After spraying each leaf with 2 ml of spore suspension (4 × 10⁶ spores/ml) the plants were kept at 100% RH for 24 hr; thereafter the humidity was lowered to 70% RH at 20°C and the photoperiod was 16 hr. Treated eggs did not become infected, but larvae that hatched from these eggs and settled on the treated abaxial leaf surface were infected at the same rate and to the same degree as treated first instar larvae. This suggests that the spores persist for at least 7 days. The final percentages of infection over all instars when treated as young eggs, old eggs, and first larval instars were 94, 93, and 90%, respectively. The final percentages of infection when treated as third and fourth larval instars and prepupae were 76, 28, and 12%, respectively. The older instars were less susceptible and adults were seldom infected by the fungus. Several applications of A. aleyrodis as a microbial insecticide are needed to achieve sufficient control of whitefly populations in glasshouses.     

Performance of Microplitis tuberculifer (Hymenoptera: Braconidae) parasitizing Mythimna separata (Lepidoptera: Noctuidae) in different larval instars

The solitary parasitoid Microplitis tuberculifer (Wesmael) is an important biological control agent of various lepidopteran pests in Asia. We examined the preference of M. tuberculifer for different instars of its common host, Mythimna separata (Walker), host instar effects on parasitoid development, and the consequences of parasitism in different stages for growth and consumption of host larvae. The wasp successfully parasitized the first four larval instars of M. separata, but not the fifth, which appeared to be behaviorally resistant. First and second instars were parasitized at higher rates compared to thirds and fourths in no-choice situations, ostensibly due to longer handling times for the latter, but second instars were most preferred in a choice test that presented all stages simultaneously. Although later instar hosts yielded heavier cocoons, the fastest parasitoid development was obtained in second instars. Lower sex ratios were obtained from first instars as females appeared to lay a smaller proportion of fertilized eggs in small hosts. Both weight gain and food consumption of parasitized larvae were reduced significantly within 24 h of parasitism, regardless of the stage parasitized, and final body weights were less than 10% those of unparasitized larvae. Thus, M. tuberculifer has good potential as a biological control agent of M. separata, successfully parasitizing the first four larval instars and dramatically reducing plant consumption by the host in all cases.     

Host-age-dependent parasitism and reproductive success of Apanteles stantoni (Hymenoptera: Braconidae), a larval parasitoid of Diaphania indica (Lepidoptera: Pyralidae)

The relative suitability of five instars of Diaphania indica (Saunders) (Lepidoptera: Pyralidae) as a substrate for the development of a larval parasitoid, Apanteles stantoni Ashmead (Hymenoptera: Braconidae), was investigated. Maximum parasitism (22.25?±?1.21%) under laboratory conditions was observed in the early larval instars. The highest parasitoid emergence was recorded from the second (86.07?±?0.70%) and third (98.93?±?0.72%) instar larvae of D. indica, and that from the first larvae was 71.43?±?1.18%. The number of cocoons in each cluster, length and width of single cocoons, percentage emergence, sex ratio and adult longevity of A. stantoni collected from different instars of D. indica were also recorded. These results indicated that the life stage of the host when the parasitoid larvae complete their final instar is particularly important for their development. Therefore, considering the efficiency of parasitism and reproduction, the second-instar larvae of D. indica is the most suitable stage for mass rearing A. stantoni in the laboratory.     

Host suitability and fitness-related parameters of Campoletis sonorensis (Hymenoptera: Ichneumonidae) as a parasitoid of the cabbage looper,Trichoplusia ni (Lepidoptera: Noctuidae)

The seven age-classes of Trichoplusia ni (Hübner) larvae evaluated in this study as hosts of Campoletis sonorensis indicates that early 2nd larval instar (3–5 day-old larvae) of T. ni represents the most suitable host stage for the development of the larval endoparasitoid C. sonorensis. The higher suitability of early 2nd larval instar of T. ni resulted in more parasitised larvae, a higher rate of successful parasitoid emergence, a higher rate of female progeny, and a lower rate of immature parasitoid mortality. The fitness gain of C. sonorensis on late 1st larval instar (2 day-old larvae) and late 2nd larval instar –early 3rd instars (6–8 day-old larvae) stages of T. ni is negatively affected by the trade-offs between the different physiological and behavioral characteristics influencing their suitability as hosts of C. sonorensis.     

Morphology and development of <Emphasis Type="Italic">Pteromalus cerealellae</Emphasis> (Ashmead) (Hymenoptera: Pteromalidae) on <Emphasis Type="Italic">Callosobruchus maculatus</Emphasis> (F.) (Coleoptera: Chrysomelidae)

Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae) is an ectoparasitoid of several stored-product insect pests. Very little information has been published on its biology and development in host larvae, which typically are concealed within seeds. We documented the development of P. cerealellae within fourth instar larvae of its concealed host, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) infesting cowpea seeds. The preimaginal life stages of the parasitoid were characterized for the first time using morphological structures revealed by microscopic techniques including scanning electron microscopy. Pteromalus cerealellae produces hymenopteriform eggs and larvae. Eggs hatch into 13-segmented first instar larvae with peripneustic condition of spiracles. The larvae have simple, tusk-like mandibles, whereas the mandibles of the pupae and the adults are of the conventional toothed types. Using statistical analyses of the sizes of the larval mandibles and head capsules in conjunction with reliable characters such as the number of exuviae on the body of parasitoid larvae, cuticular folding, and excretion of the meconium, we recorded four larval instars for P. cerealellae. The data showed significant positive correlations between larval mandible lengths and widths of larval head capsules, as well as between mandible lengths and larval instars, suggesting that mandible length is a good predictor of the number of instars in P. cerealellae. Developmental time from egg to adult emergence was ∼12 d for females and ∼11 days for males at 30 ± 1°C, 70 ± 5% r.h. and 12L:12D photoperiod.     

Artificial diets for rearing the coconut hispine beetle Brontispa longissima and its parasitoid Asecodes hispinarum

We tested artificial diets for rearing the coconut hispine beetle, Brontispa longissima, a serious invasive pest of coconut (Cocos nucifera) in Southeast Asia. We examined three artificial diets that were identical except for their agar content. The survival rate from hatching to adult emergence was 26.0% when beetles were reared on a ‘soft diet’ (20 g/l agar), 16.0% on a ‘hard diet’ (40 g/l agar), and 41.0% on a ‘mixed diet’, in which the hard diet was used for the first instar and the soft diet for later instars. Females raised as larvae on the mixed diet and then as adults on the soft diet laid few eggs, which did not hatch. However, females reared on the mixed diet as larvae and then on fresh leaves as adults consistently laid eggs that hatched. We then examined the suitability of B. longissima larvae reared on the mixed diet as hosts for the larval parasitoid Asecodes hispinarum, a specialist parasitoid of this beetle. Of the oviposited hosts, 75.0% became mummified and 41.7% produced adult wasps. These results indicate that the mixed diet may be useful for rearing B. longissima larvae as hosts for the rearing of A. hispinarum.     

Larval morphology and development of Coptera occidentalis

The morphology and development of immature stages of the solitary internal parasitoid Coptera occidentalis were studied within the pupae of their factitious host, Ceratitis capitata. Parasitoid eggs are of the hymenopteriform type. Three larval instars are described. The first instar is of the mandibulate type bearing prominent submandibular appendages and a pair of terminal lobes on the last abdominal segment. The terminal lobes are covered with cuticular spines. The integument also bears cuticular spines arranged in paired dorsal welts on each of body segments V--IX. The second and third instar larvae are hymenopteriform with simple mandibles, reduced submandibular appendages and smooth integument. The third instar has an open tracheal system with three pairs of spiracles on segments II--IV. Considerable variation in development rates of parasitoid immature stages and high percentage of superparasitism were observed. Parasitoid eggs nearly doubled in size during the 96-h incubation. Development from egg to pupa took minimum 25 days and emergence of imagines started on day 42 after parasitization. Superparasitism was recorded in 56% of the examined hosts. The average number of eggs/host was 5.04 (range 1--22). Supernumerary occurrence of successive larval instars per one host was also observed.     

Regulation of host diapause by an insect parasitoid

Abstract. 1. The interaction between larval development and parasitism by the braconid wasp Cotesia koebelei (Riley), was investigated in a population of the butterfly Euphydryas editha (Boisduval) (Nymphalidae). In this population, the butterfly host has an obligatory overwintering larval diapause.
2. It was found that E. editha larvae harbouring parasitoids were more likely to pass through an extra feeding instar before entering diapause than were non-parasitized conspecifics.
3. In addition, some individuals that were experimentally exposed to multiple parasitoid attacks bypassed diapause completely; these larvae passed through five or six feeding instars, reaching sizes typical of final instar post-diapause larvae.
4. The observed effect of superparasitism occurred regardless of whether the host larvae subsequently produced mature parasitoids, suggesting that parasitoid attack is sufficient to invoke the response.
5. It is proposed that the parasitoid C.koebelei regulates the number of pre-diapause feeding instars of its insect host E. editha, and that some component of the female venom, injected at oviposition, is responsible for this regulation.     

Life‐history traits in a parasitoid dipteran species with free‐living and obligate parasitic immature stages

The robber fly Mallophora ruficauda Weidemann (Diptera: Asilidae) is an important pest of apiculture in the Pampas of Argentina. As adults, they prey on honey bees and other insects, whereas the larvae are ectoparasitoids of Scarabaeidae grubs. Females of M. ruficauda lay eggs in grassland where the larvae drop to the ground after being wind‐dispersed and burrow underground searching for their hosts. A temporal asynchrony exists between the appearance of the parasitoid larvae and the host, with the parasitoid appearing earlier than the host. The present study investigates whether a strategy of synchronization with the host exists in M. ruficauda and determines which of the larval instars are responsible for it. Survival patterns and duration of the immature stages of the parasitoid are investigated to determine whether there is a modulation in the development at any time that could reduce the asynchrony. Experiments are carried out to determine the survival and duration of free‐living larval stadia in the absence of cues associated with the host. It is established that the first instar is capable of moulting to the second instar without feeding and in the absence of any cues related to the host, a unique event for parasitoids. Also, the first instar of M. ruficauda moults to the second stage within a narrow temporal window, and the second instar never moults in the absence of the host. After parasitizing a host, the second instar has the longest lifespan and is the most variable with respect to survival compared with the rest of the instars. All larval instars, except for those in the last (fifth) stadium, have a similar rate of mortality to that of second‐instar larvae. Additionally, it is established that the host is killed during the fourth (parasitoid) stadium and that the first‐ and fifth‐larval instars develop independently of the host. Finally, possible mechanisms that could aid in compensating for the asynchrony between the parasitoid and the host, promoting the host–parasitoid encounter, are discussed.     

Preliminary results on in vitro rearing of the endoparasitoid Cardiochiles nigriceps from egg to second instar

The composition of an artificial medium and technical procedures used for in vitro rearing of the endophagous larval parasitoid Cardiochiles nigriceps Viereck (Hymenoptera, Braconidae), from post-germ band egg to the 2nd instar larva, are described. Amino acids, carbohydrates, salts, and vitamins were supplied in defined amounts as an aqueous solution which, when supplemented with 20 mg/ml of bovine albumin, 5 mg/ml of lactalbumin (enzymatic hydrolysate), 20% (v/v) fetal bovine serum, 20% (v/v) milk and 10% (v/v) chicken egg yolk, allowed for parasitoid growth and molting to the 2nd instar. Molting to the final instar was never observed.     

Biology of Coeloides sordidator (Hymenoptera: Braconidae), a Possible Candidate for Introduction Against Pissodes strobi (Coleoptera: Curculionidae) in North America

Various aspects of the biology of Coeloides sordidator, an ectoparasitoid of pine weevils of the genus Pissodes, were studied. When reared in the laboratory on P. castaneus, females preferred to oviposit on third and fourth instar larvae in galleries, but ovipositions were also observed on second instars and prepupae. Pupae were not accepted as hosts. At 23°C and a 16 h day length, pre-imaginal development lasted 15-20 days. For each parasitoid population tested, between 8 and 28% of the individuals diapaused as prepupae in cocoons. The rate of diapause was not influenced by the photoperiod during larval development. In contrast, diapause was induced by a short day photoperiod on parents before and during oviposition and by low temperatures during the larval stage. Diapause termination was achieved by cold storage at 2°C for at least 8 weeks. Rearing of C. sordidator on P. castaneus under natural conditions showed that in the Swiss Jura it is mainly univoltine, with less than 10% of the parasitoids emerging for a second generation. When C. sordidator females were offered healthy P. castaneus larvae and larvae parasitized by the braconid endoparasitoid Eubazus semirugosus, there was no evidence that they were able to discriminate between healthy and parasitized hosts. The potential of C. sordidator as a biological control agent against the North American species P. strobi is discussed.     

Food selectivity and diel vertical distribution of Chaoborus edulis (Diptera, Chaoboridae) in Lake Malawi

1. Diel diet and vertical distribution patterns of the larval instars of Chaoborus edulis were studied in deep water near the central part of Lake Malawi, Africa.
2. First instar larvae contained very little food in their crops and probably depended on reserves from the egg. Second, third and fourth instars fed on zooplankton and were size-selective in their feeding. The mean size of prey eaten by the three instars was significantly different from each other, with larger instars feeding on larger prey. Smallest available prey was selected against and the upper size of prey was probably constrained by larval gape. Nauplii were not found in any of several thousand larvae examined. Phytoplankton did not form a significant part of the diet.
3. There was a progressive and related increase in diel periodicity in feeding and vertical migrations of successive instar stages. Fourth instars migrated particularly large distances. Such migrations removed them from their zooplankton food supply but avoided predators. A refuge from predators is probably found in or near the permanent zero oxygen boundary, at depths greater than 200 m.     

Effects of host stages and temperature on population parameters of Oomyzus sokolowskii, a larval-pupal parasitoid of Plutella xylostella

Oomyzus sokolowskii is alarval-pupal parasitoid of diamondback moth, Plutella xylostella. In a host stage preference test, the parasitoid parasitised all larval and pupal stages, but exhibited a strong preference for larvaeover prepupae or pupae, and did not show a preference among the larval instars. At 25°C, the developmental time, number and sex ratio of offspring per host pupa, and successful parasitism did not differ significantly among parasitoids reared from host larvae of different instars, indicating similar host suitability between larvae of different instars. Mean developmental times from egg to adult at 20, 22.5, 25, 30, 32.5, and 35°C were 26.5,21.0, 16.0, 12.7, 11.9 and 13.4 days, respectively. The favourable temperature range for development, survival, and reproduction of the parasitoid was 20--30°C. However, wasps that developed and emerged at a favourable temperature could parasitise effectively at 32--35°C for 24 hours. Life-fertility table studies at 20, 25, and 30°C showed that each female wasp on average parasitised 3.1, 13.2, 6.8 larvae of diamondback moth and produced 20.5, 92.1, 50.4 offspring, respectively, during her lifetime. The highest intrinsic rate of natural increase (r _m) of 0.263 female/day was reached at 30°C as a result of the short mean generation time at this temperature compared to that at 20 and 25°C, suggesting that the parasitoid had the highest potential for population growth at relatively high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Parasitoid–Pathogen–Pest Interactions of Chelonus insularis, Campoletis sonorensis, and a Nucleopolyhedrovirus in Spodoptera frugiperda Larvae

In this study we examined interactions between two solitary endoparasitoids, the braconid Chelonus insularis and the ichneumonid Campoletis sonorensis, and a multiple-enveloped nucleopolyhedrovirus infecting Spodoptera frugiperda larvae. We examined whether ovipositing females minimize interference by discriminating amongst hosts and examined the outcome of within-host competition between parasitoid species and between the parasitoids and the virus. The egg–larval parasitoid Ch. insularis did not discriminate between virus-contaminated and uncontaminated S. frugiperda eggs; all S. frugiperda larvae that emerged from surface-contaminated eggs died of viral infection prior to parasitoid emergence. The larval parasitoid C. sonorensis also failed to discriminate between healthy and virus-infected S. frugiperda larvae or between larvae unparasitized or parasitized by Ch. insularis. Host larvae parasitized in the egg stage by Ch. insularis were suitable for the development of C. sonorensis when they were multiparasitized by C. sonorensis as first, second, third, and fourth instars, whereas emergence of Ch. insularis was dramatically reduced (by 85 to 100%) in multiparasitized hosts. Nonspecific host mortality was significantly higher in multiparasitized hosts than in singly parasitized hosts. The development time and sex ratio of C. sonorensis in multiparasitized host larvae were unaffected by the presence of Ch. insularis larval stages. Both Ch. insularis parasitized and nonparasitized larvae of the same instar (second, third, or fourth instars) had a similar quantitative response to a challenge of virus inoculum. All host larvae that ingested a lethal dose of virus were unsuitable for Ch. insularis development. In contrast, C. sonorensis did not survive in hosts that ingested a lethal virus dose immediately after parasitism, but parasitoid survival was possible with a 2-day delay between parasitism and viral infection and the percentage of parasitoid emergence increased significantly as the interval between parasitism and viral infection increased. The development time of C. sonorensis was significantly reduced in virus-infected hosts compared to conspecifics that developed in healthy hosts. C. sonorensis females that oviposited in virus-infected hosts did not transmit the virus to healthy hosts that were parasitized subsequently. Field applications of virus for biocontrol of S. frugiperda may lead to substantial mortality of immature parasitoids, although field experiments have not yet demonstrated such an effect.