Oviposition behavior of Edovum puttleri, reared on two hosts, Leptinotarsa decemlineata and L. texana

Female Edovum puttleri Grissell [Hymenoptera: Eulophidae], reared from eggs of Leptinotarsa decemlineata (Say) or Leptinotarsa texana Schaeffer [Coleoptera: Chrysomelidae], were videotaped as they attacked egg masses of L. decemlineata containing 20 host eggs. We identified 15 components of ovipositional behavior. Parasitoids reared on L. texana attacked and oviposited in significantly more host eggs than did females reared on L. decemlineata. Ethometric analyses of behavioral transitions and a clustering analysis of 34 behavioral parameters showed that females reared on L. texana attacked the host egg mass in a different manner than those reared from L. decemlineata. It was concluded that differences were associated with the host species upon which they were reared. Contrary to previous reports, mortality of unparasitized hosts was caused by an ovipositor probe of short duration, which was not related to host-feeding.     

Reproductive biology of two biotypes of Edovum puttleri, a parasitoid of Colorado potato beetle eggs

Emergence of adults of Edovum puttleri Grissell (Hymenoptera: Eulophidae) has a diel periodicity: most emergence occurred within 2 h of lights on (16L:8D, 24±1°C). Males emerged 2.0±3.0 h prior to females, and soon thereafter mated with emerging females. Courtship behavior did not differ between the Colombian and Mexican biotypes and was similar to that of members of the eulophid subfamily Tetrastichinae. The preoviposition period and oviposition period did not differ between biotypes. Males and females of both biotypes were long-lived, with the longevity of females of the Mexican biotype being significantly longer than that of Colombian females. males of both biotypes lived equally long. Mexican females produced more offspring than Colombian females, although this difference was not significant. After approximately 3 weeks, production of female offspring declined in both biotypes. A single mating was sufficient for females to produce a full complement of female offspring. Head capsule width of females correlated positively with fecundity.

---

Résumé L'émergence des adultes de E. puttleri Grissell (Hymen.: Eulophidae) présente une périodicité quotidienne, la plupart de émergences ayant lieu dans les deux premières heures de la photophase (16L/8D, 24°±1°C). Les mâles apparaissent 2±3 h avant les femelles, et s'accouplant immédiatement avec les femelles émergentes. Les biotypes mexicains et columbiens ont le même comportement de cour, qui correspond à celui décrit pour les Tetrastichini et pour les Entedontinae. Il en est de même pour la durée, d'une part des périodes précédent la ponte (3,7 ±2,8 j), et d'autre part de la ponte elle-même (25,1 ±4,5 j). Les adults des deux biotypes vivent longtemps, mais les femelles mexicaines vivent plus longtemps (57,4±18 j) que les colombiennes (46,2±14,8 j); les longévités des mâles sont identiques (45,7 ±18 j). Les femelles mexicaines produisent apparemment plus d'oeufs (221,2±29,5) que les colombiennes (166,6±58,1), mais ces différences ne sont pas significatives. Après trois semaines environ la production de descendants régresse chez les deux types. Un seul accouplement suffit à produire le contingent total de filles. La largeur de la capsule céphalique des femelles est liée positivement à leur fécondité.

     

Parasitization by Edovum puttleri (Hymenoptera: Eulophidae) in relation to host density in the field

Abstract.

• 1 The relationship between parasitization by Edovum puttleri Grissell and density of eggs of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), was studied on two spatial scales (eggs mass and 6 m² cage).
• 2 For both scales, rates of parasitism were generally inversely related to host density for periods ranging from 2 to 8 days after parasitoid release. Thereafter, parasitism became independent of host density.
• 3 The initial inverse-density relationship and subsequent shift to density independence may result from several factors: (1) ambient temperatures, (2) the parasitoid's limited egg production, (3) differential times of exposure of egg masses to parasitoids, and/or (4) the parasitoid's patterns of host feeding and oviposition.
• 4 Although overall levels of parasitism were relatively low, total mortality of L.decemlineata eggs (including nonviable and cannibalized eggs, and those killed by parasitoid feeding) in parasitized egg masses was consistently high (?70–90%).

     

Use of the egg parasiteEdovum puttleri [Hym.: Eulophidae] in an IPM system developed for Colorado potato beetle [Col.: Chrysomelidae] control on potatoes,Beltsville, Maryland

Edovum puttleri Grissell in conjunction with the fungal pathogenBeauveria bassiana (Balsamo) Vuillimen, a β-exotoxin ofBacillus thuringiensis varthuringiensis Berliner, and the insect growth regulator triflumuron (Alsystin 4F) were evaluated in a pest management system to control Colorado potato beetle,Leptinotarsa decemlineata (Say). Soil treatments ofB. bassiana had no significant impact on emerging Colorado potato beetle adults. Foliar applications of the β-exotoxin and triflumuron significantly reduced 1 ^st larval generation. Releases ofE. puttleri resulted in 56 % egg mass parasitization, significant reduction of 2 ^nd generation larvae, and significantly higher potato yields.Leptinotarsa texana (Schaeffer) was successfully used as an alternate host for production ofE. puttleri.      

Parasitism ofLeptinotarsa decemlineata [Coleoptera: Chrysomelidae] byEdovum puttleri [Hymenoptera: Eulophidae] in different cultivars of eggplant

Experiments were conducted to quantify parasitism of Colorado potato beetle,Leptinotarsa decemlineata (Say), by the egg parasitoid,Edovum puttleri Grissell, on 3 different cultivars of eggplant,Solanum melongena L. Levels of parasitism were higher (P<0.05) on ‘Black Pride’ than on other cultivars. The percentage of egg masses that were parasitized was 1.2-fold higher (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’. The number of eggs per mass that were parasitized was 1.3- and 1.4- fold greater (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’, respectively. The percentage of eggs that were parasitized per mass and percentage of emerged adult parasitoids did not differ (P>0.05) among cultivars; between 2.1- to 2.6- fold more females than males emerged from eggs on all cultivars during the growing season.Edovum puttleri suppressed the 2nd generation ofL. decemlineata on ‘Black Pride’ and ‘Harris Special’, but did not suppress populations on ‘White’.      

Edovum puttleri [Hym.: Eulophidae]: Biological activity and responses to normal and frozen eggs ofLeptinotarsa decemlineata [Col.: Chrysomelidae]

Biological control of eggplant pests in general, and (CPB)Leptinotarsa decemlineata (Say) in particular, is highly problematic.Edovum puttleri Grissell, an exotic egg parasitoid which has been found potentially effective, is being reared to this end. Frozen CPB eggs (?18°C) proved to be accepted and suitable for parasitization byE. puttleri. However, when given a choice between 20 frozen and 20 normal eggs every 2 days, the females exhibited a significant preference for the latter. Parasitization and host predation patterns related to female age are described by 2 opposing fourth-order polynomial functions. Parasitization increased up to day 10, followed by progressive decline. Average life span per female was 31.10±.58, with a recorded maximum of 56 days. High predatory behaviour of older females, which showed a decrease in parasitization, was observed in these experimental conditions.     

Effects of selected physical and chemical treatments of Colorado potato beetle eggs on host acceptance and development of the parasitic wasp, Edovum puttleri

Effects of various physical and chemical treatments of Colorado potato beetle [Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)] eggs on parasitization and development of the egg parasitoid Edovum puttleri (Hymenoptera: Eulophidae) were investigated. UV irradiation did not affect host acceptance but reduced host suitability for UV exposure times 90 min. Susceptibility of host eggs to UV irradiation varied with host age; eggs were most vulnerable to damage from irradiation at 12, 18, and 24 h post-oviposition. The rate of parasitization also was influenced by host age. Percent parasitization was greatest in freshly laid eggs and 24–30 h old eggs. Seventy-seven percent of host eggs frozen at –20 °C (5 min) were parasitized by E. puttleri, but extended exposure of eggs to –20 °C reduced both acceptance and suitability. Host eggs that had been washed with hexane (removal of kairomone and sticky layer) also were parasitized. After 5 min of washing, application of kairomone significantly increased the rate of parasitism (from 74.7% to 88.2%), but with longer periods of washing, kairomone application had no significant effect on percent parasitism. Thus, the sticky material(s) coating the egg did not appear to be essential for parasitization to occur. Our results provide effective methods and times for treating Colorado potato beetle eggs to maximize parasitization and development of E. puttleri.     

In vitro rearing of Edovum puttleri, an egg parasitoid of the Colorado potato beetle, from egg to pupal stage in artificial diets devoid of insect sources: Effects of dietary amino acid and carbohydrate levels

Previous studies have demonstrated that Edovum puttleri, an egg parasitoid of the Colorado potato beetle, can be reared through the pupal stage in an artificial diet containing either hemolymph from Manduca sexta or CPB embryonic cell line-conditioned medium. In order to improve the diet and reduce production costs, i.e., eliminate the insect-derived components, the effects of 13 amino acids and 20 carbohydrates on the growth and development of the parasitoid were determined. In the presence of any one of five of the amino acids (arginine, glutamine, lysine, threonine and valine) at a concentration of 1%, or eight of the carbohydrates (cellobiose, fructose, gentiobiose, glucose, lactose, melinbiose, sorbitol and threhalose), also at a concentration of 1%, more than 75% of the larvae molted to the second instar. At higher concentrations (2 and 3%), all five of the amino acids and most of the eight sugars promoted third instar formation. Prepupal formation was also observed. In the presence of threonine (at 2 and 3%) or glutamine (at 3%), between 22 and 29% of the parasitoids formed prepupae. Of the six sugars (at 3%) that promoted prepupal formation, lactose and sorbitol which promoted 18 and 20% prepupation, respectively, were the most effective. In the presence of all 13 amino acids (each at 3%) or all 20 carbohydrates (each at 3%), 36 and 39%, respectively, of the parasitoids formed prepupae. At lower concentrations, reduced percentages of prepupal formation were observed. Since the amino acids, glutamine and threonine, and the sugars, fructose, gentiobiose, glucose, lactose, sorbitol and trehalose, when added individually to the diet (at a concentration of 3%) were most effective in promoting prepupal formation, the effect of one of these two amino acids in combination with each of the six sugars was tested. Glutamine in combination with lactose or sorbitol was able to promote pupation (6.3%), and threonine in combination with any one of five of the sugars (lactose and sorbitol were most effective) supported pupal formation (6.7%). Our study demonstrated that E. puttleri can be successfully reared from the egg through the pupal stage in an artificial diet devoid of insect materials.     

Incidence of natural enemies of the Colorado potato beetle,Leptinotarsa decemlineata [Coleoptera: Chrysomelidae] on a native host in Mexico

In central Mexico, the center of origin forLeptinotarsa decemlineata (Say) and its principal host plants,L. decemlineata is associated with a diverse complex of natural enemies. Observations during 2 years in Morelos, Mexico revealed 4 species of asopine pentatomids, 7 species of foliar searching carabids, and 2 coccinellids among the predators ofL. decemlineata. Parasitoids include 3 species of tachinids andEdovum puttleri Grissel, an eulophid egg parasitoid. These natural enemies include several predators that have not previously been reported attackingL. decemlineata. University of Maine Agriculture Experiment Station No. 1553     

Propagation of the Colorado potato beetle [Col.: Chrysomelidae] egg parasiteEdovum puttleri, [Hym.: Eulophidae]

The parasitic wasp,Edovum puttleri Grissell, was successfully reared onLeptinotarsa decemlineata (Say) in the laboratory and increased in sufficient numbers for inoculative release studies in the spring and summer. The effects of temperature on parasite development, and host-parasite ratios in the laboratory are presented. The sex ratio of parasites reared in the laboratory are compared to those released and recovered in the field.     

Potential for the biological control ofLeptinotarsa decemlineata [Col.: Chrysomelidae] by the egg parasite,Edovum puttleri [Hym.: Eulophidae] in Maryland, 1981–84

The biological control potential ofEdovum puttleri Grissell, an exotic egg parasite ofLeptinotarsa decemlineata (Say), was examined in experimental potato plots. The parasite does not overwinter in Maryland, but through annual inoculative releases it consistently parasitized Colorado potato beetle (CPB) egg masses throughout the season. Approximately 50% of all egg masses collected were parasitized and maximum parasitism byE. puttleri occurred in egg masses produced by first generation adults.Edovum puttleri reproduced and maintained itself in potato plots for 15 weeks. The random sampling of CPB egg masses to evaluate the parasite in the field is described.      

Superparasitism and host size effects in Oomyzus sokolowskii, a parasitoid of diamondback moth

Many aspects of a parasitoid's biology may be affected by its host. Host size, for example, could affect parasitoid fitness, especially in gregarious parasitoids, in which the resource is used by multiple siblings. Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) is a gregarious larval–pupal endoparasitoid of the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), a major pest of crucifers worldwide, and is able to superparasitize the host. This study focuses on the hypothesis that because resource availability is higher in larger hosts, parasitoids developing in larger hosts will fare better. However, superparasitized hosts are expected to yield larger numbers of parasitoid offspring of smaller body size. Results showed that superparasitism increased the number of parasitoid offspring produced per host and increased offspring longevity, but decreased offspring body size. However, developmental time and sex ratio of parasitoid offspring was similar among hosts parasitized once, twice, or three times. Regardless of superparasitism, parasitoids emerging from larger hosts that were fed honey solution lived longer than similarly fed progeny from smaller hosts (36.4 vs. 22.1 days). The results partially support the hypothesis that Oomyzus gained fitness from an increase in host size; moreover, superparasitism seems advantageous for Oomyzus due to increased offspring numbers and longevity.     

Cascading effects of host size and host plant species on parasitoid resource allocation

1. The bottom‐up factors that determine parasitoid host use are an important area of research in insect ecology. Host size is likely to be a primary cue for foraging parasitoids due to its potential influence on offspring development time, the risk of multiparasitism, and host immunocompetence. Host size is mediated in part by host‐plant traits that influence herbivore growth and potentially affect a herbivore's quality as a host for parasitoids. 2. Here, we tested how caterpillar host size and host plant species influence adult fly parasitoid size and whether host size influences wasp parasitoid sex allocation. We measured the hind tibia lengths and determined the sex of wasp and fly parasitoids reared from 11 common host species of polyphagous caterpillars (Limacodidae) that were in turn reared on foliage of seven different host plant species. 3. We also tested how host caterpillar species, host caterpillar size, and host and parasitoid phenology affect how the parasitoid community partitions host resources. We found evidence that parasitoids primarily partition their shared hosts based on size, but not by host species or phenology. One index of specialisation (d′) supports our observation that these parasitoids are quite generalised within the Limacodidae. In general, wasps were reared from caterpillars collected in early instars, while flies were reared from caterpillars collected in late instars. Furthermore, for at least one species of solitary wasp, host size influenced sex allocation of offspring by ovipositing females. 4. Host‐plant quality indirectly affected the size attained by a tachinid fly parasitoid through its direct effects on the size and performance of the caterpillar host. The host plants that resulted in the highest caterpillar host performance in the absence of enemies also yielded the largest parasitoid flies, which suggests that host plant quality can cascade up to influence the third trophic level.     

Assessing augmentative releases of parasitoids using the «Recruitment method», with reference toEdovum puttleri,a parasitoid of the colorado potato beetle [Coleoptera: chrysomelidae]

Release of approximately 17,700 experienced adult femaleEdovum puttleri Grissell against 1^st generation Colorado potato beetle eggs in 1987 in a 0.4 ha potato field in S. Deerfield, Massachusetts resulted in only 3.6% parasitism as assessed by direct measurement of host and parasitoid recruitment. Levels of non-viability indicated an additional 2.8% of hosts killed by parasitoid hostfeeding, for an overall impact of 6.4%. Release in 1988 of 126,300 parasitoid against 1^st generation hosts in a 0.4 ha potato (Solanum tuberosum L.) field at the same site produced only slightly higher levels of parasitism (10.6%) and host feeding (2.0%). Release in 1987 of 32,800 wasps against 2^nd generation eggs resulted in only 0.7% parasitism and 0.3% host feeding due to the toxicity of fenvalerate (Pydrin^R) residues from a single application applied for control of the potato leafhopper,Empoasca fabae (Harris). Release in 1988 of 47,400 wasps against the 2^nd host generation in the absence of any pesticide applications resulted in 34.4% parasitism and 16.1% host feeding, for a total impact of 50.5%. Difference in parasitization levels between host generations supports the idea thatE. puttleri adults require an in-field carbohydrate source such as aphid honeydew to reproduce. In Massachusetts, aphid populations in potato typically do not develop until the end of the 1^st larval generation. The recruitment method ofVan Driesche & Bellows (1988) proved to be a satisfactory approach for determining results of augmentative parasitoid releases.      

Catching Ariadne by her thread: how a parasitoid exploits the herbivore's marking trails to locate its host

Chemical signals that can be associated with the presence of a host insect often work as arrestants in close range host location by parasitoids, leading to longer searching times on patches where such signals are present. Our current view of parasitoid host location is that by prolonging the search times in patches, randomly searching parasitoids enhance their chance of detecting host insects. However, prolonged search times are not necessarily the only modification in parasitoid behaviour. In this study, we examine the exploitation of host-fruit marking pheromone of rose-hip flies, Rhagoletis basiolaOsten-Sacken (Diptera: Tephritidae) by the specialized egg-larval parasitoid Halticoptera rosae Burks (Hymenoptera: Pteromalidae). We provide evidence that the instantaneous probability that a host egg will be located by a searching parasitoid wasp differs markedly between pheromone-marked and unmarked fruits. The arresting response to the marking pheromone, i.e., the prolonged time a wasp is willing to search on marked fruits, can only account for a small fraction of the difference in successful host location on marked and unmarked fruits. We further demonstrate that the time wasps require to locate the host egg is independent of the size of the rose-hip harbouring the fly egg, and thus is independent of the area the wasp potentially has to search. A comparison of our findings with results of different search algorithms for parasitoid wasps suggests that wasps use the fly's pheromone marking trail as a guide way to the fly's oviposition site and thus the host egg.     

Influence of host species and age on host preference of Trissolcus semistriatus

Trissolcus semistriatus(Hymenoptera: Scelionidae) has a high potentialfor being an effective biological control agentfor the sunn pest, Eurygaster integriceps.This study was conducted to determine thepreferences of T. semistriatus in termsof host species and age of variousheteropteran host eggs (E. integriceps,Dolycoris baccarum, Graphosoma lineatum,Eurydema ornatum, Holcostethus vernalis). Theresults indicated that a small portion ofparasitism of E. ornatum eggs wasobtained (28.5%), although high parasitismrates were found in other host eggs(90.0–80.0%). A high percentage of adultemergence was also recorded. When tested for its ability toparasitize host eggs of different ages,T. semistriatus was found to preferyounger hosts: it showed parasitism ratesgreater than 50% with up to 3 daysold E. integriceps and D.baccarum, and with up to 4 days old G. lineatum and H. vernalis. However, theparasitism rates in all the ages of E. ornatum eggs were much lower than for other hostspecies. The developmental times in all hostspecies at different ages was extended withincreased host age. It was concluded that G. lineatum and D. baccarum could beused for mass production of egg parasitoids.     

Plant and host effects on the leafroller parasitoid Dolichogenidia tasmanica

Parasitism by the braconid wasp Dolichogenidia tasmanica of first instar larvae of the lightbrown apple moth Epiphyas postvittana, established on four different species of potted host plants, was assessed after 2 weeks of field exposure in an apple orchard. Parasitism varied significantly between larval host plants (apple 58%, broom 59%, clover 30%, poplar 19% ). Parasitism on potted apple seedlings of the co-evolutionary host, E. postvittana, was compared in a field trial with that of two native New Zealand leafroller species (to which D. tasmanica has had exposure for 5 decades only). Parasitism varied significantly with larval host (E. postvittana, 83%; Ctenopseustis herana, 58%;Planotortrix octo, 26% ). Larval collections were made from mature apple trees and identification of larvae was achieved by DNA analysis for the leafroller species using PCR-RFLP of ITS1 + ITS2, and for the parasitoid by specific PCR of partial 18S. Parasitism under natural field conditions on mature apple trees was not different between larval hosts (mean 32.5% ). In laboratory studies, more P. octo larvae departed in response to parasitoid probing behaviour than E. postvittana, which is likely to contribute to the difference in parasitism rates. This study conclusively shows that D. tasmanica parasitises native New Zealand leafrollers, despite their different evolutionary origins.     

Masking of host plant odour in the olfactory orientation of the Colorado potato beetle

The odour of potato plants Solanum tuberosum L., elicits a true odour-conditioned positive anemotaxis in the Colorado potato beetle, Leptinotarsa decemlineata Say. Blending the odour of non-host plant species, namely wild tomatoes Lycopersicon hirsutum f. glabratum C.H. Mull or cabbage Brassica oleracea L. var. gemmifera DC., with the attractive host plant odour blocks the release of upwind responses in non-experienced as well as experienced females. The neutralization of the beetle's orientation responses is obtained without repellency. It is expected that masking of host plant odour occurs often in mixed cropping systems.

---

Résumé Un certain nombre d'articles rapporte une diminution du nombre des insectes phytophages spécialistes comme une conséquence à la diversification des agroécosystèmes (Altieri & Letourneau, 1982; Cromartie, 1981; Kareiva, 1983; Risch et al., 1983). Ainsi, il a été supposé que la présence de plantes non-hôtes pouvait interférer avec celle de plantes hôtes en modifiant la nature des informations chimiques parvenant aux insectes. Les modifications comportementales qui peuvent en résulter lors de l'attraction à distance sont toutefois encore peu claires. Les expérimentations présentées ici analysent les réponses individuelles du doryphore à diverses stimulations olfactives issues de plantes entières. Des femalles ont été ainsi étudiées un jour après l'émergeance en présence d'air vierge et d'air chargé d'odeurs de Solanum tuberosum, Lycopersicon hirsutum f. glabratum, Brassica oleracea var. gemmifera, ainsi que des mélanges, S. tuberosum avec L. hirsutum et S. tuberosum avec B. oleracea. A partir de l'enregistrement continu de l'activité locomotrice dans chaque condition (à l'aide du compensateur de locomotion), nous avons déterminé que L. hirsutum et B. oleracea masquaient l'odeur de la plante hôte S. tuberosum en supprimant la réponse anémotactique positive conditionnée par l'odeur de cette dernière. Les mélanges d'odeurs ainsi obtenus sont considérés comme neutres pour l'orientation à longue distance du doryphore. L'expérience préalable par le doryphore de l'ingestion de feuillage de pomme de terre ne modifie pas l'effet du camouflage obtenu. Ces résultats laissent penser qu'il est possible de limiter la découverte de la plante hôte chez les insectes, et que les méthodes de camouflages olfactives pourraient prévenir les attaques de certains ravageurs.

     

In vitro rearing of Edovum puttleri,an egg parasitoid of the Colorado potato beetle,on artificial diets: Effects of insect cell line‐conditioned medium

Effects of conditioned media prepared from cell lines derived from 11 insect species (six families, three orders) on the in vitro growth and development of the egg parasitoid Edovum puttleri were investigated. The parasitoid exhibited significantly different responses to the various insect cell line‐conditioned media that were incorporated into the artificial diets. When cell lines were derived from embryos, higher percentages of 3rd instars and prepupae were observed than when cell lines were derived from fat body or ovaries. Medium conditioned with cell line IPLB‐CPB2 derived from the embryos of the Colorado potato beetle produced the best result. Preconditioning time was important. In general, 5 days of preconditioning appeared to be optimal. The growth‐ and development‐promoting effect may have resulted from growth factors or growth‐supporting factors produced/ released by the insect cell lines into the culture medium. Upon storage at 0–4°C for 7–14 days, the ability of cell line‐conditioned medium to promote development beyond the second instar was greatly reduced (approximately 10–55%). Our studies demonstrated that to support the in vitro growth and development of E. puttleri, insect hemolymph could be successfully replaced with insect cell line‐conditioned medium. These findings should facilitate the development of a cost‐effective mass‐rearing system for E. puttleri and/or other parasitoids. Arch. Insect Biochem. Physiol. 40:173–182, 1999. Published 1999 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.     

The effect of host nutrition on growth and development of the parasitoid waspVenturia canescens

We investigated the effect of host (Plodia interpunctella; Lepidoptera: Pyralidae) nutritional status on development of the solitary endoparasitoid,Venturia canescens (Hymenoptera: Ichneumonidae). Parasitoids from 3rd (L3) instars reared on a deficient diet during early parasitism took longer to develop and suffered higher mortality than those reared from hosts fedad libitum although there was not a significant difference in the size of eclosing wasps from the two groups. L5 hosts reared at high density produced smaller parasitoids, which developed more rapidly than those reared from hosts from low density containers, although mortality was higher in the latter. In a separate experiment we starved groups of 10–20 hosts (parasitized as L3) daily beginning on the 4th day after parasitism, to determine the host developmental stage required for successful parasitoid development to eclosion. Parasitoid survivorship increased with length of host access to food, while the egg-to-adult parasitoid development time increased throughout the experiment. Parasitoid size decreased with increasing periods of host starvation. The successful emergence ofVenturia depends uponPlodia reaching the size normally attained in the mid-5th instar, or 50–70% of the mass of healthy late 5th instars. Our results show that when earlier instars are parasitized, host growth is essential for successful parasitoid development to eclosion. Furthermore, they suggest that, for many koinobionts, host suitability may be greatly influenced by feeding rate and food quality.