Behavioral response of the egg parasitoid <Emphasis Type="Italic">Ooencyrtus telenomicida</Emphasis> to host-related chemical cues in a tritrophic perspective

The response of the generalist egg parasitoid Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) to host-related chemical cues from tomato plants, Solanum lycopersicum L., and adults of Nezara viridula (L.) (Heteroptera: Pentatomidae) was investigated in laboratory-based no-choice and paired-choice tests. In Y-tube olfactometer experiments, when female wasps were exposed to volatiles from plants in different conditions, they were attracted only to volatiles produced by N. viridula adult-infested tomato plants. When female wasps were exposed to adults of N. viridula, they were attracted to volatiles from virgin males, and, at a lower level, to volatiles from mated females in preoviposition state. Finally, studies in open arena showed that chemical footprints left by adults of N. viridula did not induce arrestment responses in wasp females. These results are discussed in terms of extrinsic competition with other beneficial egg parasitoids that in field can compete for the same egg mass, since intraguild interactions may affect the success of a biological control program.     

The role of host semiochemicals in parasitoid specificity: a case study with Trissolcus brochymenae and Trissolcus simoni on pentatomid bugs

The role of semiochemicals on host specificity of two egg parasitoid species, the European Trissolcus simoni and the American Trissolcus brochymenae (Hymenoptera: Scelionidae), was studied in an olfactometer and in different arenas. Cues from two allopatric pests of cabbage, the European Eurydema ventrale and the American Murgantia histrionica (Heteroptera: Pentatomidae), and from the polyphagous and cosmopolitan Nezara viridula were tested. Both T. simoni and T. brochymenae responded to volatile and contact cues from their co-evolved hosts E. ventrale and M. histrionica, respectively, thus confirming the role of host semiochemicals in host location and recognition. When cues of non-co-evolved hosts were presented, a partial “new association” was obtained, as T. simoni probed and oviposited in M. histrionica eggs and some adult emergence occurred. However, this association is unlikely to occur in the field because T. simoni did not respond to volatile cues of M. histrionica. Instead T. brochymenae partially responded to volatile and contact cues from E. ventrale, but eggs were rarely accepted and parasitoids did not develop in this host. When N. viridula was tested, T. simoni responded only to contact cues, whereas T. brochymenae partially responded to volatile and contact cues, but N. viridula eggs were not suitable for development. Therefore, the N. viridula–T. brochymenae association reported from the literature appears unreliable. Understanding the mechanisms that result in host specificity may help increase parasitoid safety and predict their efficacy in biological control with old or new associations.     

Generalism Versus Specialism: Responses of Diadegma mollipla (Holmgren) and Diadegma semiclausum (Hellen), to the Host Shift of the Diamondback Moth (Plutella xylostella L.) to Peas

A population of the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) (DBM) was recently found to infest sugar snap- and snowpeas in the Rift Valley in Kenya, causing heavy damage. The influence of this host shift on host location preferences of two parasitoids was investigated: The indigenous Diadegma mollipla (Holmgren) regarded as a relative generalist, and Diadegma semiclausum(Hellen), regarded as highly specific to DBM. The attractiveness of different odour sources was compared for the two parasitoid species using a Y-tube olfactometer using naïve females. D. mollipla was not significantly attracted to any cabbage related odours but showed a significant preference for the DBM infested pea plant when tested against clean air. D. semiclausum was highly attracted to the undamaged cabbage plant and odours related to cabbage. On the other hand, peas infested with DBM, showed no attractiveness to this parasitoid. The results showed that specialisation of D. semiclausum is mediated by host plant signals, associated with crucifers, which are not encountered in DBM feeding on peas. For D. mollipla,although a frequent parasitoid on DBM in crucifers, volatiles emitted by these plants might not be used as primary cues for host location. This species may respond largely to chemicals yet unknown and associated with a variety of plant-herbivore interactions.     

The Effect of Seasonal Changes on Nezara viridula (L.) (Hemiptera: Pentatomidae) and Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) in Hawaii

The effect of seasonal changes in temperature and photoperiod on the interaction of Nezara viridula (Hemiptera: Pentatomidae) and its egg parasitoid Trissolcus basalis (Hymenoptera: Scelionidae) was investigated in the laboratory. We found no evidence of reproductive diapause in N. viridula under simulated Hawaiian summer and winter conditions. Further, although “diapause” coloration was obtained in the laboratory, it was not correlated with reproductive status. Studies of the survival of T. basalis provided with honey under the same simulated conditions showed that under summer conditions, only 2.1% of the female and 13.5% of the male population were still alive by 60 days. When provided with N. viridula egg masses at 30 days, 79.4% of the eggs were parasitized in a 3-h period. Under winter conditions, 54.3, 28.3, and 14.5% of the females were alive at 30, 60, and 90 days after adult emergence. When provided with N. viridula egg masses at 30, 60, and 90 days for 3 h, 57.6, 32.8, and 47.1% of the eggs were successfully parasitized. These studies suggest the limiting factor in the interaction of T. basalis and N. viridula is not reproductive diapause, but instead the ability of T. basalis to survive summer conditions.     

Selective responses of Trissolcus basalis and Telenomus podisi to chemical footprints of preferred hosts

Chemical trails of the hosts (footprints) are important cues for the host searching behaviour of egg parasitoids of the family Scelionidae. The present study aims to determine the influence of the footprints of three neotropical stink bugs (Euchistus heros, Dichelops melacanthus and Nezara viridula) on the foraging behaviour of two parasitoids, Trissolcus basalis and Telenomus podisi, as well as a possible selective response to fooprints of their preferred hosts. Accordingly, Tr. basalis and Te. podisi females are allowed to forage on open arenas where E. heros, D. melacanthus or N. viridula had walked or on open arenas that had been treated with samples of an extract from each stink bug's footprints. Hexane extracts of stink bug footprints are obtained from solvent-washed Petri dishes where insects were allowed to walk for 24 h, and these extracts were analyzed by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Each parasitoid responds selectively to the footprints of their preferred host (Tr. basalis to footprints of N. viridula and Te. podisi to footprints of E. heros). Twenty-six compounds comprising of C18 to C35 (saturated and unsaturated) and methyl branched hydrocarbons were identified in extracts of E. heros, D. melacanthus and N. viridula, respectively. There are significant differences in the total amount of the compounds identified in the footprint stink bug's extracts and also a difference in the amounts of individual compounds. In addition, the behavioural assays showed that footprints of stink bugs are stimuli that are used by egg parasitoids to search, discriminate and selectively locate their preferred host.     

Distribution, host specificity, and overwintering of Celatoria bosqi Blanchard (Diptera: Tachinidae), a South American parasitoid of Diabrotica spp. (Coleoptera: Chrysomelidae: Galerucinae)

The genus Diabrotica (Coleoptera: Chrysomelidae) includes a great number of pest species, including some of the most important crops pests of the Americas. However, only five parasitoid species have been recorded for it. The parasitoid Celatoria bosqi Blanchard was the first parasitoid described from Diabrotica spp. in South America, where substantial parasitism has been observed. C. bosqi has been collected almost throughout the South American distribution of its main host, Diabrotica speciosa (Germar), in an area that includes temperate and tropical lowlands, and semiarid to humid highlands. Three Diabrotica species were found to host the parasitoid, D. speciosa (Germar), Hystiopsis sp., and Diabrotica viridula (F.), with a total parasitism of 2.60, 5.55, and <0.02%, respectively. Laboratory experiments with field beetles and puparia, reared in the laboratory, indicate that C. bosqi overwinters obligatorily in overwintering adult host beetles, remaining quiescent in its live host below developmental temperatures. Based on the known climatic range of C. bosqi, and its requirement of adult overwintering hosts, a potential distribution in North America is projected.     

Intraguild interactions between two egg parasitoids exploring host patches

Intraguild interactions between two egg parasitoids, Trissolcus basalis (Hymenoptera: Scelionidae) and Ooencyrtus telenomicida (Hymenoptera: Encyrtidae), exploring egg masses of the Southern Green Stink Bug (SGSB) Nezara viridula (Heteroptera: Pentatomidae), were investigated in laboratory conditions by single, simultaneous and sequential host attack experiments. Mortality of N. viridula eggs was higher in simultaneous and sequential releases compared to single species releases. In simultaneous host exploitations, T. basalis females displayed an aggressive behavior against O. telenomicida females. The outcome of multiparasitism showed that interspecific larval competition was dominated by O. telenomicida regardless of the sequence in which oviposition occurred and which parasitoid was or was not simultaneously released in the patch. Finally, O. telenomicida can successfully develop in hosts already parasitized by T. basalis up to seven days earlier, acting as a facultative hyperparasitoid, so that intraguild predation (IGP) also occurred. The ecological factors that allow species coexistence and the role played by competition in biological control programs are discussed.     

Fecundity and Longevity of Green Vegetable Bug,Nezara viridula, Following Parasitism byTrichopoda giacomellii

The effects of parasitism by the ArgentinianTrichopoda giacomellii(Blanchard) on reproduction and longevity of its host,Nezara viridula(L.) are reported. Parasitoid larvae suppress egg maturation, reducing by 70% the fecundity of mature female hosts during the period of larval development. Egg viability was not affected, but mating frequency was reduced by approximately 50%. When parasitized as newly eclosed adults, 84% of females fail to reproduce. In male hosts, fertility and mating frequency were not affected during the period of larval parasitoid development. In male and reproductively immature female hosts, death was coincident with, or occurred shortly after parasitoid emergence (2–4 days); in mature females, death occurred on average 2 weeks after larval parasitoid emergence. Host mortality occurred as a consequence of tissue damage incurred as the parasitoid larvae emerged from the host. Some individuals survived parasitism though no further reproductive activity (mating or oviposition) occurred. The effectiveness ofT. giacomelliias a biological control agent is discussed in relation to its impact on reproduction and survival of its host and contrasted with the action of otherTrichopodaspecies.     

Olfactory response of three parasitoid species (Hymenoptera: Braconidae) to volatiles of guavas infested or not with fruit fly larvae (Diptera: Tephritidae)

The olfactory responses of the native parasitoids Doryctobracon areolatus (Szépligeti) and Asobara anastrephae (Muesebeck) and of the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) to guava (Psidium guajava L.) infested or not with fruit fly larvae were evaluated. D. areolatus and D. longicaudata females responded to the odors of uninfested rotting guavas, although D. areolatus was also attracted to fruits at the initial maturation (turning) stage. The females of these species recognized the volatiles of guavas containing Ceratitis capitata (Wied.) larvae. However, in bioassays involving fruits with larvae of different instars, D. longicaudata females were not able to separate between fruits containing C. capitata larvae at the initial instars and larvae at the third instar. In the evaluations of volatiles released by guavas containing C. capitata and Anastrepha fraterculus (Wied.) larvae, the D. longicaudata females were oriented toward the volatiles of fruits containing both host species, but differed significantly from volatiles of guavas containing C. capitata larvae. The D. areolatus females also showed responses to both species, although with a preference for volatiles of fruits containing A. fraterculus larvae. The A. anastrephae females were oriented toward the odors of fruits infested with both fruit fly species. In the shade house, D. longicaudata females were oriented to volatiles of rotting fruits containing larvae or not, but could not significantly differentiate between hosts. D. areolatus females were not attracted toward fruits on the ground in the shade house, regardless of host, suggesting that this parasitoid does not forage on fallen fruits.     

The ovipositing female of Ooencyrtus telenomicida relies on physiological mechanisms to mediate intrinsic competition with Trissolcus basalis

Ongoing studies by our group showed that the outcome of the intrinsic competition between two solitary egg parasitoids, Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) and Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae), is dominated by O. telenomicida. In this article we investigated the role played by the ovipositing O. telenomicida female in the suppression of a T. basalis competitor. Laboratory experiments were conducted by allowing an O. telenomicida female to puncture the eggs of Nezara viridula (L.) (Heteroptera: Pentatomidae) with her ovipositor (= no oviposition) or to parasitize them. The results show that O. telenomicida relies on some physiological mechanisms to mediate its interspecific intrinsic competition with T. basalis. In fact, the emergence of T. basalis was strongly reduced in host eggs that were parasitized either before or after being punctured by O. telenomicida at fixed time intervals (5, 15, 30, or 45 h). The low percentage of emergence of T. basalis (ranging from approximately 4–20%) was a consequence of the delay and growth rate reduction of larval development. Furthermore, the percentage of eclosion of N. viridula nymphs was negatively affected by the O. telenomicida female’s punctures (96% from healthy host eggs, 4% from punctured host eggs). Host eggs punctured or oviposited in by O. telenomicida showed alterations in the ooplasm including some melanized‐like areas near the hole made with the ovipositor; such alterations indicate that the adult parasitoid releases substances that affect the host eggs survival. These results suggest that the O. telenomicida female influences both the physiological interspecific parasitoid‐parasitoid interaction, as well as the host‐parasitoid interaction, providing, for the first time in egg parasitoids, evidence that physiological suppression of some competitive egg parasitoids is mediated by the ovipositing female.     

Mating Behavior of Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae): Potential for Outbreeding in a Predominantly Inbreeding Species

The mating behavior of the quasi-gregarious egg parasitoid Trissolcus basalis (Wollaston) was investigated under field conditions. Trissolcus basalis has female-biased sex ratios and is a protandrous species, with males emerging 1–2 days before females. Males competed aggressively for control of the egg mass, with one male assuming dominance and control of the egg mass, although changes in dominance occurred at least once on each egg mass observed. Typical mating behavior involved the dominant male mating his sisters immediately upon their emergence from the egg mass. These behaviors are characteristic of an inbreeding species that manifests local mate competition. However, several aspects of the mating behavior of T. basalis are inconsistent with that of an inbreeding species. Over 18% of emerging females were not mated by the dominant male upon emergence, 13% of females were not observed to be mated at all and may have left their natal site as virgins, 25% of females were mated multiple times and sometimes by multiple males, females remained near the natal site for up to several hours after emergence before emigrating, and males dispersed away from the natal site during female emergence. Trissolcus basalis may be a predominantly inbreeding species but its emergence and mating behavior suggest that low-frequency outbreeding is also likely to occur.     

Multiple host use by the egg parasitoid Trissolcus basalis (Wollaston) in a soybean agricultural system: biological control and environmental implications

1 Species of bugs (Hemiptera: Pentatomidae and other families) that are parasitized by the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) in the soybean agricultural system on the Darling Downs in south-eastern Queensland, Australia, are reported. The degree to which eggs of each bug species are used by T. basalis is quantified, which allows assessment of the role of these alternative host species in the biological control of the green vegetable bug Nezara viridula (L.). 2 Egg masses of nine species of pentatomid bugs and one unidentified bug species were collected. Parasitism rates of egg masses of all species averaged 50–70% but were significantly lower for the more important pest species, including the green vegetable bug, than for some of the agriculturally less important species. 3 Trissolcus basalis emerged from nearly all species collected and was the major parasitoid to emerge from most species. A number of native species were parasitized heavily by T. basalis and parasitism of such species may enhance biological control of the green vegetable bug, but may also pose environmental concerns. Parasitism of predatory bugs by T. basalis may have a negative impact on the biological control of other pests, especially lepidopterous pests. 4 Although the impact of T. basalis on native and predatory host species was not directly quantified, these host species remain abundant and therefore do not appear to be affected adversely by such high rates of parasitism.     

Vine mealybug sex pheromone increases citrus mealybug parasitism by Anagyrus sp. near pseudococci (Girault)

The present study was aimed at elucidating the role of lavandulyl senecioate (LS), the sex pheromone of Planococcus ficus, in host selection of the parasitoid Anagyrus sp. near pseudococci. Field trials were carried out in Portugal, Italy and Israel. The effect of LS on the parasitism rate of the wasp was determined by exposing sentinel mealybugs combined with pheromone dispensers impregnated with LS, in comparison with other baits: lavandulyl isovalerate (LI); planococcyl acetate (PAc); and unbaited control traps. In addition, in order to study the host location behavior of A. sp. near pseudococci, pheromone dispensers were placed at three different distances: inside the trap, 30 or 60 cm away from the trap. The number of parasitoid females inside the traps, the number of parasitized mealybugs, and the number of days required for the first parasitoid emergence were recorded. The response of A. sp. near pseudococci females to different doses of LS (25–1350 μg) was also evaluated using sticky plate traps. The rate of mealybug parasitism by A. sp. near pseudococci was significantly increased by LS in the three parasitoid populations. PAc and LI had no significant effect on the wasp parasitism rate in most of the trials. However, the Italian population of the parasitoid responded to PAc, showing apparently a different behavioral pattern. The number of parasitoid females trapped did not significantly differ between tested doses of LS. The use of LS as an arrestant in host location by the A. sp. near pseudococci female is discussed.     

Biology of Australian and United States strains of Trissolcus basalis,a parasitoid of the green vegetable bug,Nezara viridula

Strains of Trissolcus basalis (Wollaston) Hymenoptera: Scelionidae, an egg parasitoid of the green vegetable bug, Nezara viridula (L.), were obtained from three regions of Australia and from Homestead, Florida (USA). Percent parasitoid emergence was approximately the same for freezer-stored (-75°C) and fresh eggs, and freezer-stored eggs were suitable hosts for a longer time. Optimum host age, oviposition and emergence patterns, mean number of progeny per female, sex ratio and longevity were examined and certain comparisons were made between the Australian and USA parasitoids. Genetic crosses made between males and females of each strain revealed that reproductive isolation did not occur. Higher fecundity of the Australian strains may make them more successful than indigenous (USA) strains for controlling pest populations of N. viridula in the southern USA.     

Host specificity of the egg pupal parasitoid Fopius arisanus (Hymenoptera: Braconidae) in La Reunion

Fopius arisanus is a polyphagous parasitoid of Tephritidae, which has been recently introduced to La Réunion Island as part of a classical biological control programme. We carried out laboratory experiments to assess the host specificity of this parasitoid, initially reared on Bactrocera zonata, and then offered for parasitization the eight local tephritid pest species. Naive or experienced parasitoid females were given tephritid eggs in no choice tests. Fopius arisanus females parasitize all fly species but parasitism varies with host species. No adult wasps emerge from Bactrocera cucurbitae and the survival of this species is only slightly affected by parasitism. Dissections show that the late instars of this fly may eliminate the parasitoid by encapsulation. When developing on Ceratitis capitata, Ceratitis rosa, Dacus ciliatus, Dacus demmerezi, and Neoceratitis cyanescens, parasitoid survival rate ranges from 10 to 25%. Bactrocera zonata and Ceratitis catoirii are the best hosts, yielding parasitoid survival rates of more than 70% with no premature mortality. The egg-larval mortality of C. capitata, C. rosa, D. ciliatus, and N. cyanescens, and the pupal mortality of D. demmerezi, are significantly increased by parasitism. The size of emerging adults is affected by host species and is correlated to pupal weight. Bactrocera zonata would be a favorable host to support routine colonization of F. arisanus for mass production of this parasitoid.     

Host location in Oomyzus gallerucae (Hymenoptera: Eulophidae), an egg parasitoid of the elm leaf beetle Xanthogaleruca luteola (Coleoptera: Chrysomelidae)

Eggs of the elm leaf beetle Xanthogaleruca luteola are often heavily attacked by the chalcidoid wasp Oomyzus gallerucae. We studied the chemical signals mediating interactions between the egg parasitoid, its host, and the plant Ulmus campestris. Olfactometer bioassays with O. gallerucae showed that volatiles of the host-plant complex attract the parasitoid. In order to determine the source of attractive volatiles within this host-plant-complex, we tested separately the effect of odours of eggs, gravid elm leaf beetle females, faeces of the beetles and elm twigs (with undamaged leaves and leaves damaged either mechanically or by feeding of the beetles). Odours of faeces of the elm leaf beetle were attractive, whereas neither volatiles from eggs nor from gravid females acted as attractants. Volatiles from undamaged or damaged plants did not elicit a positive reaction in O. gallerucae, whereas volatiles from feeding-damaged plants onto which host eggs had been deposited were attractive. This latter result suggests that it is not feeding but deposition of host eggs onto elm leaves that induces the production of plant volatiles attractive to the egg parasitoid. Investigations of the search patterns of O. gallerucae within the habitat by laboratory bioassays revealed that the egg parasitoid encounters host eggs by chance. Contact kairomones from faeces were demonstrated to be important in microhabitat acceptance, while contact kairomones isolated from the host eggs are relevant for host recognition. Received: 12 February 1997 / Accepted: 29 April 1997     

Cross-mating tests and the species status of Trissolcus basalis reared from the eggs of differentheteropteran species

Laboratory choice and no-choice cross-mating tests were conducted to establish whether Trissolcus basalis individuals from green vegetable bug, Nezara viridula, and nine other host species sharemating characteristics and belong to the same species. In no-choice cross-mating tests, all individuals in self- and out-crosses mated within 10 minutes. Although all females mated, they were not all inseminated successfully. However, a similar proportion of females was inseminated across all self- and out-crosses in each set of cross-mating tests. Mate-choice tests indicated that males and females selected mates at random. Overall, the results indicate that T. basalis individuals from the ten host species represent a single genetical species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Production of Anagrus epos Girault (Hymenoptera: Mymaridae) on Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs

Anagrus epos Girault (Hymenoptera: Mymaridae) is a natural enemy candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology or ecology of A. epos when it utilizes GWSS eggs as a host. Here, we report the results of laboratory studies that describe the host age preference for oviposition, longevity of A. epos adults provided with different food sources, and developmental rates at six different constant temperature regimes. Anagrus epos is a gregarious parasitoid in GWSS eggs with up to 14 adults emerging from each GWSS egg. In choice and no-choice tests for oviposition, A. epos females successfully parasitized all developmental ages of GWSS eggs (1–8 days old). In choice tests, parasitism rates were significantly higher in 1-, 3-, 4-, and 5-day-old GWSS eggs than in 2-, 6-, 7-, and 8-day-old eggs. If provided with honey and water, honey only, water only, or no food or water, A. epos females lived on average 8.2, 4.7, 2.6, and 1.6 days, respectively. Anagrus epos required 294.1 degree-days above a lower temperature threshold of 12.4 °C to develop from egg to adult (eclosion). Our results provide baseline information useful in the development of an efficient parasitoid mass rearing program for A. epos release and evaluation in California.     

Mate Finding Via a Trail Sex Pheromone by <Emphasis Type="Italic">Aphytis melinus</Emphasis> DeBach (Hymenoptera: Aphelinidae) Males

Finding mates is frequently problematic for parasitoid wasps. In some parasitoid species, males rely on volatile, airborne sex pheromones for locating mates, while in others they rely on contact, trail sex pheromones. This study sought to shed light on the mate finding mechanism of males of Aphytis melinus. Specifically, the goal was to determine whether A. melinus males use airborne or contact pheromones, or both, for locating mates. The study showed that A. melinus males rely on a contact, trail sex pheromone for locating mates: A. melinus males responded to substrate-borne cues left by virgin females, while they did not respond to airborne cues from virgin females. Specifically, males more frequently encountered virgin females when the females walked across an arena to a fixed encounter point compared to when they were manually placed at the encounter point, and spent greater than expected time on surfaces previously visited by virgin females compared to control surfaces not visited by females. In contrast, males did not respond to airborne cues from virgin females in an airflow olfactometer nor to traps baited with virgin females in the field, and spent similar lengths of time on surfaces visited by newly-mated or 24-h mated females versus control surfaces not visited by females. The main effect of the trail sex pheromone on the behavior of A. melinus males was to direct their search and, so, increase the likelihood of encountering mates. This effect apparently is not preceded by longer-range attraction of males via an airborne female sex pheromone. Overall, the results of this study support a hypothesis in which A. melinus males searching on substrates on which females may be present rely exclusively on a trail sex pheromone to locate mates.     

Influences of plant species on life history traits of Cotesia rubecula (Hymenoptera: Braconidae) and its host Pieris rapae (Lepidotera: Pieridae)

The relative suitability of four plants was studied for larvae of Pieris rapae L. and its parasitoid Cotesia rubecula (Marshall). For unparasitized P. rapae, pupal dry weight and egg-pupa growth rate were higher on cabbage, radish and nasturtium than on Indian hedge mustard. Larval developmental rate and size were greatest for C. rubecula when its host was feeding on nasturtium. Wasp survival was not affected by the host insect/plant combination in which the parasitoid developed. These results indicate that the plant on which host larvae feed is an important factor in development of the parasitoid.