Solitary Parasitoid Research Articles

Weather Parameter’s Impact on Natural Parasitization by Campoletis chlorideae Uchida in Chickpea Ecosystem - New Alluvial Zone of West Bengal

Background: A major biotic constraint in chickpea (Cicer arietinum L.) production is gram pod borer, Helicoverpa armigera (Hübner). However, the population of this pest is reduced to some extent by a solitary endo-larval parasitoid, Campoletis chlorideae Uchida under field conditions. Climate change has a greater impact on natural enemies’ effectiveness used in field-level pest management. Therefore, the present study was conducted to understand the impact of weather factors on C. chlorideae parasitization rate of H. armigera in chickpea grown in the new alluvial agro-climatic zone of West Bengal. Methods: Chickpea was grown in a randomized complete block design (RCBD) with three replications during Rabi 2017-18, 2018-19 and 2019-2020, at Mondouri farm, Bidhan Chandra Krishi Visawavidayala, Mohanpur, West Bengal. To know the most significant weather parameter which influences C. chlorideae parasitization or parasitoid incidence, H. armigera larvae (2nd instar) collected from the field experiment were reared until cocoon formation and parasitization % was correlated with weather parameters and subsequently subjected to stepwise regression analysis. Result: The larval endo-parasitoid, C. chlorideae marked its first appearance from 3rd SMW after the appearance of H. armigera and its activity was high (68% to 72% parasitization) during the flowering to pod initiation stage and thereafter declined gradually. Among the weather variables, only temperature (maximum and minimum) had a consistent and significant negative correlation with C. chlorideae incidence and was responsible for nearly 50% C. chlorideae incidence. An increase in 1°C temperature results in a decrease of 4% parasitoid incidence. Thus, climate change in the near future will have a considerable influence on the overall survival, development and rate of parasitization of parasitoids.

Mango headspace volatiles trigger differential responses of the mango fruit fly Ceratitis cosyra and its parasitoids

Before the introduction of Bactrocera dorsalis (Hendel) to sub-Saharan Africa, Ceratitis cosyra (Walker) was economically the most important pest in mango farming. Its native natural enemy, the solitary parasitoid Psyttalia cosyrae (Wilkinson), played a crucial role in C. cosyra bio-control, later complemented by the exotic parasitoids Diachasmimorpha longicaudata (Ashmead) and Fopius arisanus (Sonan) among Integrated Pest Management (IPM) systems. To understand the in situ mango-C. cosyra-parasitoid tritrophic interaction, we assessed the responses of the fruit fly and the three parasitoids to headspace volatiles from various mango conditions. These conditions included non-infested mature unripe mangoes, C. cosyra-infested mangoes, 7th- and 9th-day post-infestation mangoes, non-infested ripe mangoes of three varieties (Kent, Apple, and Haden), and clean air (blank). We also compared the fruit fly's performance in the mango varieties and identified the chemical profiles of mango headspace volatiles. Ceratitis cosyra was attracted to both infested and non-infested mangoes (66–84 % of responsive C. cosyra) and showed superior performance in Kent mango (72.1 % of the 287 puparia recovered) compared to Apple and Haden varieties. Fopius arisanus displayed a stronger attraction to the volatiles of C. cosyra-infested mangoes (68–70 %), while P. cosyrae and D. longicaudata were significantly attracted to the 9th-day post-infestation mangoes (68–78 %) compared to non-infested mango volatiles. Gas chromatography-mass spectroscopy showed substantial quantitative and qualitative differences in volatile profiles among mango treatments. Esters predominated in non-infested ripe, 7th- and 9th-day post-infestation mangoes, while monoterpenes and sesquiterpenes were most dominant in the other treatments. The in situ experiments underscored varying preferences of the species for mango headspace volatiles and their subsequent treatments. These results provide valuable insights for further exploration, specifically in identifying the key volatiles responsible for species responses, to facilitate the development of applicable selective semiochemicals for managing species of African fruit fly.

A new species of Uscanoidea Girault (Hymenoptera, Trichogrammatidae), an egg parasitoid of Monalonion dissimulatum Distant (Hemiptera, Miridae)

A new species of Uscanoidea Girault (Hymenoptera: Trichogrammatidae), Uscanoidea ricoi Viggiani, Gamboa & Pérez-Benavides, sp. nov., is described and illustrated. The species is a solitary egg parasitoid of Monalonion dissimulatum Distant (Hemiptera: Miridae), the main insect pest on cocoa crops. An identification key for the described Uscanoidea species of the world is provided. The new species has a high potential for the biological control of the true bug M. dissimulatum in cocoa plantations in the Neotropical region.

Parasitism success of Microplitis manilae (Hymenoptera: Braconidae) on different diet‐fed Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae

AbstractEfficient rearing is necessary for the successful biological control of pests. The braconid wasp, Microplitis manilae, is a natural solitary parasitoid of larval Spodoptera frugiperda. However, the effect of the host diet on the parasitism success of M. manilae on S. frugiperda larvae remains unclear. Here, we determined the parasitism rate, oviposition, eclosion rate, developmental period and offspring sex ratio of M. manilae parasitizing S. frugiperda fed with fresh corn leaves or an artificial diet. M. manilae parasitizing the corn leaf‐fed S. frugiperda larvae exhibited a significantly higher parasitism rate (40%), oviposition (62.50 eggs/female) and eclosion rate (81.38%) than the wasp parasitizing the artificial diet‐fed S. frugiperda larvae (22%, 38.33 eggs/female, and 58.73%, respectively). Furthermore, M. manilae parasitizing the corn leaf‐fed S. frugiperda larvae exhibited a significantly shorter developmental period (16.35 days) and lower sex ratio (1.17) than the wasp parasitizing the artificial diet‐fed S. frugiperda larvae (18.00 and 2.15 days, respectively). Overall, M. manilae exhibited better parasitic success on corn leaf‐fed S. frugiperda larvae than on artificial diet‐fed S. frugiperda larvae. Therefore, using fresh corn leaf‐fed S. frugiperda is the most suitable strategy for mass‐rearing M. manilae for pest biocontrol. Our findings suggest M. manilae as an effective biocontrol candidate for controlling S. frugiperda in corn fields.

Status of Natural Enemies and Entomopathogens on New Invasive Pest Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) under Maize Ecosystem in Indian Subcontinent

The pests’ natural enemies were explored by collecting FAW eggs and larvae from maize fields. The survey also revealed natural parasitism by egg parasitoids viz., Telenomus sp. (Hymenoptera: Platygastridae) and Trichogramma sp. (Hymenoptera: Trichogrammatidae), gregarious larval parasitoid Glyptapanteles creatonoti (Viereck) (Hymenoptera: Braconidae) solitary larval parasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae), and a solitary indeterminate larval-pupal (Hymenoptera: Ichneumonidae: Ichneumoninae) parasitoid. Spodoptera frugiperda is the first host record for G. creatonoti across the globe. The parasitiods were raised in the laboratory for emergence, recognition and effectiveness as natural enemies. Cotesia or Apanteles spp. were concluded to occur since emerged. Besides these, other commonly found bioagents viz., Forficula sp. (Dermaptera: Forficulidae) and entomopathogenic fungus Nomuraea rileyi (Farl.) Samson was also collected in large numbers. Therefore, the occurrence of Spodoptera frugiperda natural enemies in India represents for advocacy campaign to include their use into IPM strategies that enhance and permit bio agents to boom for control of fall armyworm.

N-octyl acrylate is a candidate sex pheromone component involved in courtship in parasitoid wasp Microplitis mediator.

Sex pheromones are considered to play critical roles in partner communication of most parasitic Hymenoptera. However, the identification of sex pheromone components remains limited to a few families of parasitoid wasps. In this study, we functionally characterized a candidate sex pheromone component in Microplitis mediator (Hymenoptera: Braconidae), a solitary parasitoid of Noctuidae insects. We found that the body surface extract from female wasps could significantly stimulate courtship behavior of males. Gas chromatography-electroantennographic detection (GC-EAD) analysis revealed that a candidate semiochemical from extract triggered significant electrophysiological response of antennae of males. By performing gas chromatography-mass spectrometer (GC-MS) measurement, GC-EAD active compound was identified as n-octyl acrylate, a candidate sex pheromone component in female M. mediator. In electroantennogram (EAG) tests, antennae of male wasps showed significantly higher electrophysiological responses to n-octyl acrylate than those of females. Y-tube olfactometer assays indicated that male wasps significantly chose n-octyl acrylate compared with the control. Furthermore, male wasps showed a remarkable preference for n-octyl acrylate in a simulated field condition behavioral trial; simultaneously, n-octyl acrylate standard could also trigger significant courtship behavior in males. We propose that n-octyl acrylate, as a candidate vital sex pheromone component, could be utilized to design behavioral regulators of M. mediator to implement the protection and utilization of natural enemies.

Anagonia lasiophthalma (Diptera: Tachinidae): Survey, identification, and biological traits of a new biological control agent of the Eucalyptus snout beetle, Gonipterus platensis (Coleoptera: Curculionidae)

The Eucalyptus snout beetle, Gonipterus platensis, is one of the main pests of eucalypts outside its native range. Among the available control methods for this pest, classical biological control with Anaphes nitens (Hymenoptera: Mymaridae) has been the most widely used, but it is not always effective. To identify other natural enemies that might provide further pest control, a field survey was conducted in Tasmania, Australia, in which Anagonia spp. were found to parasitize 7 % of Gonipterus spp. larvae. One species was subsequently identified as the solitary parasitoid Anagonia lasiophthalma, based on direct comparisons with research collection material in Australia. To assess the potential of this species as a biological control agent, A. lasiophthalma was reared on G. platensis larvae under quarantine conditions, and its biology and reproductive strategy were studied in the laboratory. Global mating success was 58 %, with 66 of the 114 A. lasiophthalma females analyzed mating within an established 10-day period. Most females mated within 48 h after emergence and started to parasitize about a week later. Dissections of mated females showed that this species is ovolarviparous, incubating its eggs in an ovisac, before inserting them “ready-to-hatch” directly into the host using a piercing structure derived from the modification of a sternite in the female terminalia. Over the course of their lifetime, females on average produced 35 offspring and post-mortem dissections revealed an additional 32 eggs in the ovisac. Longevity of females and males was similar, ranging between 55 and 84 days, but females maintained without host larvae lived longer than females exposed to host larvae. These results provide relevant information to improve laboratory rearing protocols and suggest that A. lasiophthalma may be effective against the snout beetle in its invaded range.

Oviposition fluids from adult wasps mediate interspecific competition between parasitoid larvae

Abstract Parasitoid wasp larvae engage in intense interspecific competition when sharing a host insect, with lethal consequences for the losers. Larval parasitoid competition is generally thought to be resolved by physical traits, such as enlarged mandibles. Although solitary parasitoid larvae are typically superior competitors against gregarious larvae, such physical traits are unlikely to be effective against large numbers of competitors. Larval competition may instead be mediated by maternal factors that increase the survival of offspring facing interspecific competition, thus increasing parental fitness. When laying eggs inside a host, many female parasitoids also inject oviposition fluids that are known to suppress host immune responses, permitting successful offspring development. We explored whether the oviposition fluids of two wasp species in the genus Cotesia (Cotesia rubecula, a strong competitor that almost always wins interspecific competition against a weaker competitor, Cotesia glomerata) might also represent maternal factors that improve the interspecific competitive ability of their offspring. We demonstrate that injections of both venom and calyx fluid from C. rubecula can inhibit egg hatching and larval development of C. glomerata. Venom from C. rubecula decreased C. glomerata egg development by 2.7 times, and calyx fluid injections caused deformities in 23% of developing C. glomerata. In contrast, reciprocal injections of the oviposition fluids from C. glomerata did not inhibit the development of C. rubecula. Our results show that maternal factors can improve the interspecific competitive ability of parasitoid larvae, challenging the previous assumptions that larval competition was resolved primarily through physical combat or larval secretions.

Biology and morphometric relationship of gall inducers Contarinia sp. and corresponding parasitoids for swollen galls of Nitraria sibirica pall.

Galls function as provide shelter for gall inducers, guarding them against their natural enemies. Previous research has illuminated the interactions between galls, gall inducers, and their corresponding parasitoids within various caltrop plants. However, less is known about these relationships within Nitraria sibirica, particularly regarding the efficacy of parasitism. Therefore, this study aimed to identify the morphometric relationships among the swollen galls, gall inducers, and their parasitoids. Two species of gall inducers and three species of parasitoids were obtained from the swollen galls of N. sibirica. The correlations of the parasitization indexes, the lifespan of gall inhabitants, and temperature and the morphometric relationships between the galls and their inhabitants were analyzed. The dominant gall inducer identified was Contarinia sp. (Diptera: Cecidomyiidae). Furthermore, it was observed that three solitary parasitoids attacked Contarinia sp. in the swollen galls, with only Eupelmus gelechiphagus acting as an idiobiont ectoparasitoid. The dominant parasitoids were Platygaster sp. and Cheiloneurus elegans at sites 1 and 2, respectively, with Platygaster sp. displaying greater abundance than C. elegans in the swollen galls. The lifespan of the gall inhabitants shortened gradually as the temperature increased. Moreover, the optimal number of gall chambers ranged from two to four per swollen gall with maximized fitness, which can be considered the optimal population density for the gall inducer Contarinia sp. Morphometric analysis exhibited a strong linear correlation between gall size and chamber number or the number of gall inhabitants, as well as a weak correlation between gall size and body size of the primary inhabitants of swollen galls. Our results highlight the importance of the biological investigation of parasitoids and gall inducers living in closed galls with multiple chambers and may pave the way for potential application in biological control.

Self‐superparasitism, oviposition order, and delay: does offspring survival explain host exploitation strategies of females under interspecific competition in a solitary parasitoid wasp?

AbstractIf the risk of larval competition is high and its consequence on offspring mortality is important, we expect female behavioural strategies favouring the survival of their offspring to be selected for. In parasitoids, hosts can be parasitized several times, in some cases by females of different species (i.e., multiparasitism). In solitary parasitoids, only one offspring can develop per host: supernumerary individuals are eliminated through larval competition. Under these conditions, mothers can lay additional eggs in/on the same host (i.e., self‐superparasitism) to increase the chances of one of their offspring winning the competition. They can also aggressively protect their offspring against competing females to prevent them from multiparasitism and ovicide. Both strategies (self‐superparasitism and host defence) are observed in females of the solitary ectoparasitoid wasp, Dinarmus basalis Rondani (Hymenoptera: Pteromalidae), when facing females of another solitary ectoparasitoid species, Eupelmus vuilleti (Hymenoptera: Eupelmidae), during host exploitation. Here, we aimed to explore whether D. basalis females' behaviours relate to their offspring survival chances during larval competition: we expect mothers to defend their hosts only during the vulnerability period of their offspring and self‐superparasitize to increase the chances of their offspring winning the larval competition. We thus measured the effect of oviposition order (D. basalis females oviposited first or second), delay between ovipositions (30–60 min or 3–4 h) and the occurrence of D. basalis females' self‐superparasitism on D. basalis offspring survival when competing with E. vuilleti juveniles. Our results showed D. basalis offspring constantly had a lower survival probability than E. vuilleti offspring. Only being laid first increased D. basalis offspring survival rate, whereas the time delay between ovipositions and self‐superparasitism did not significantly increase it further. The fact that offspring survival chances under interspecific competition may not be the main driver of maternal host protection and self‐superparasitism is discussed.

Family Scoliidae as parasitoids of (Insecta: Hymenoptera) beetles (Insecta: Coleoptera)

Scoliidae waxes are solitary parasitoids from scarab beetle larvae. Female Scoliidae throws themselves into the ground in search of these larvae and then paralyze them with a string. Before laying the egg, they sometimes dig up the chamber and move the paralyzed beetle larva into it. Scoliidae wasps act as important biocontrol agents because many of the beetles they parasitize are pests, including the Japanese beetle. Male Scoliidae guards the territory, ready to mate with females emerging from the ground. Adult wasps can be flower pollinators of some plants and can find it on many flowers in late summer. The purpose of this paper is to describe the Family Scoliidae as parasitoids of (Insecta: Hymenoptera) beetles (Insecta: Coleoptera). For this, a bibliographic survey of Scoliidae was carried out oufromin the years 1971 to 2021. Only complete articles published in scientific journals and expanded abstracts presented at national and international scientific events were considered. Data were also obtained from Plataforma: Academia.edu, Frontiers, Qeios, Pubmed, Biological Abstract, Publons, Dialnet, World, Wide Science, Springer, RefSeek, Microsoft Academic, Science and ERIC.

Effects of male age, body size and mating status on female mate preference and offspring sex ratio in Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae)

Mate choice is one of the main components of sexual selection, with females usually considered to be the selective sex. Male status is an important factor that affects female choice and to a large extent female mating preference. Pachycrepoideus vindemmiae (Rondani) (Hymenoptera: Pteromalidae) is an important solitary ectoparasitic idiobiont parasitoid that attacks several fly species and thus can be used as a biological control agent. We explored the influence of male status on mate selection, fecundity and offspring sex ratio. The results show that (1) P. vindemmiae females prefer to mate with young and large males and tended to choose males with only one mating experience; (2) the age, body size and mating status of males did not significantly affect female fecundity; and (3) the proportion of male offspring was larger when females mated with older, small and more often mated males. These results show that P. vindemmiae females prefer to mate with young and large males that had mated few times, and that mating with these males results in a higher proportion of female offspring. In addition, this study also indicates the way of rearing P. vindemmiae that produce more female offspring for use as biological control agents.

POTENSI PENGENDALIAN HAYATI HAMA SPODOPTERA FRUGIPERDA UNTUK KEBERLANJUTAN PRODUKSI JAGUNG

The armyworm Spodoptera frugiperda, which damages corn plants, is one of the invasive pests. The armyworm S. frugiperda damages corn plants by eating leaf tissue from one side so that the remaining epidermal tissue then makes holes in the leaves and eats from the edge of the leaf to the inside, which causes perforation in the leaves. Control efforts using insecticides have not been practical due to the feeding behaviour of the second and third instar larvae that settle on the inside of the leaves under protected conditions. Therefore, it is necessary to carry out other control techniques that can suppress the development of environmentally friendly S. frugiperda by considering economic and ecological aspects, namely biological control.
 Biological control optimizes the role of natural enemies as biological control agents in efforts to manage pest populations which are part of the chain in agroecosystems. Utilization of natural enemies, parasitoids, predators, and pathogen, can suppress the development of the S. frugiperda pest in corn, reducing the use of synthetic pesticides. Natural enemies of S. frugiperda include the egg parasitoid Telenomus sp. and Trichogramma sp.; larva parasitoid Glyptapanteles creatonoti (Viereck), solitary larval parasitoid Campoletis chlorideae Uchida, and parasitoid larvae of the order Hymenoptera: Ichneumonidae: Ichneumoninae and G. creatonoti. as well as an entomopathogenic species, Nomuraea rileyi (Farl.) Samson. Natural enemies can control S. frugiperda pests to save sustainable maize yields based on the basic principles of sustainable agriculture models. Agroecological steps are taken to reduce the population of S. frugiperda in corn plants by:/ (1) sustainable management of soil fertility, primarily actions that maintain or store soil organic carbon; (2) intercropping with properly selected companion plants; and (3) diversification of the agricultural environment through the management of (semi) natural habitats at various spatial scales.

The Antennal Sensory Structures of Female Anagyrus vladimiri (Hymenoptera: Encyrtidae).

The Encyrtidae (Hymenoptera) encompasses a large group of parasitic wasps widely used in biocontrol programs of scale insects (Hemiptera: Coccoidea). Anagyrus vladimiri is a solitary parasitoid that attacks and develops on several mealybugs of economic importance. Thus, this species is widely used as a biocontrol agent of Planococcus spp. and Pseudococcus spp. A. vladimiri males and females show sexual dimorphism with regard to the antennal organization, in terms of shape and the development of antennomeres. Ultrastructural investigations of female antennae, carried out with scanning (SEM) and transmission (TEM) electron microscopy, revealed the presence of nine distinct antennomeres. The scape was enlarged and paddle-like, compared to the other antennomeres. The club (the apical antennomere) was mono-segmented and housed the highest number of sensilla. Eight morphologically different types of sensilla were described; sensilla trichoidea I, trichoidea II, chaetica I, chaetica II, grooved peg sensilla, campaniform sensilla, multiporous plate sensilla and multiporous basiconic sensilla. Ultrastructural investigations allowed for us to assign a specific function to each type of sensilla. The most abundant type of sensilla were sensilla trichoidea I and multiporous plate sensilla. We also found two types of sensilla (multiporous basiconic sensilla and sensilla chaetica II) that were present only on the females.

A new model formulation for host depletion in parasitoids

A new model of host depletion in the functional response of parasitoids is presented. Most existing models describe the dynamics of prey consumption as a sequential-memoryless/Markovian process of searching for, handling, and consuming prey, but the feeding interaction between a parasitoid and its host is different. One of the most important characteristics is that the host is not consumed, and remains in the arena. On the other hand, functional response models of solitary parasitoids assume that each host can accommodate an infinite number of oviposition events without being killed or becoming unsuitable as a host without the parasitoid noticing it. As a consequence, host depletion is never considered in parasitoid functional response models. To solve that issue, we extended the traditional random predator and random parasitoid functional response models of Rogers into a compartmental model formulated with ordinary differential equations, to group hosts with a different number of attacks to simulate how the parasitoid spreads the attacks between already parasitized and non-parasitized hosts. This model was further modified to simulate non-sequential memoryless search, handling and oviposition. We studied the behaviour of these models to understand how a variation of their parameters led to different shapes of functional response curves and statistical distributions of the number of parasitoid eggs laid per host. The results showed that the expected curves differ from those predicted by the simpler Holling's disk equation (type II functional response), random parasitoid models (no depletion), and the random predator model (proportional depletion). Finally, the non-sequential-memoryless models predict straight curves resembling a type I functional response at low host densities.

Laboratory Evaluation of Pupal Parasitoids for Control of the Cornsilk Fly Species, Chaetopsis massyla and Euxesta eluta.

Cornsilk flies are serious pests of sweet corn through damage to cobs and secondary fungal establishment. As pupae are generally outside the infested cob on the ground, there can be potential for use of pupal parasitoids for control. Two species of gregarious parasitoids, Muscidifurax raptorellus and Nasonia vitripennis, and three species of solitary parasitoids, Spalangia endius, Spalangia cameroni and Muscidifurax raptor, were evaluated against pupae of the two cornsilk fly species, Euxesta eluta and Chaetopsis massyla. House fly pupae, the most common host for most of the parasitoids, were included for comparison. All of the parasitoids killed and successfully parasitized pupae of the two cornsilk fly species at rates that were similar to house fly pupae. Adult parasitoids that emerged from cornsilk fly hosts were somewhat smaller than parasitoids reared from house flies and had proportionally fewer females. These parasitoids, which are widely and commercially available for filth fly control, warrant further consideration for their potential against cornsilk flies in the field.

Effects of Host Ages and Release Strategies on the Performance of the Pupal Parasitoid Spalangia endius on the Melon Fly Bactrocera cucurbitae

The melon fly, Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), is a quarantine pest that causes considerable economic losses to growers of vegetables and fruits worldwide. Spalangia endius (Walker) (Hymenoptera: Pteromalidae) is a solitary pupal parasitoid of various dipteran hosts. We assessed the impact of the host pupal age (2, 4, and 6 days old), host density (5, 10, 15, 20, 25, and 30), and parasitoid density (1, 2, 3, 4, 5, and 6) on the parasitizing potential of S. endius on B. cucurbitae pupae under laboratory conditions. The effects of different soil depths on the parasitism rate of S. endius and the dispersal behavior of S. endius at distances of 0, 5, and 10 m were also evaluated under field conditions. The results showed that the parasitism rate of S. endius significantly increased with the increase in host density and parasitoid density. The host pupal age did not influence the number of pupae parasitized by S. endius and the progeny sex ratio of S. endius under different host densities. In the fields, different puparium burial depths of B. dorsalis pupae significantly influenced the parasitism and eclosion rates of S. endius but did not influence the eclosion rate of B. cucurbitae. Spalangia endius females could travel up to 10 m to parasitize at a similar rate on B. cucurbitae pupae compared to S. endius placed at 0 m.

Landscape composition affects parasitoid body size in species-specific manner: A case study in Asian rice systems

The top-down effect of natural enemies on pests is a crucial ecosystem service supporting integrated pest management. However, the variation in morphological traits of parasitoids in different landscape contexts and the differences in parasitoid emergence rate caused by this variation are still poorly known. We measured the inter-tegular distance (ITD) and body mass of three parasitoids– Cotesia chilonis (Munakata), Eriborus sinicus (Holmgren), and Microgaster russata Haliday – on overwintering larvae of Chilo suppressalis (Walker), the rice stem borer (RSB), collected from 20 rice paddies along a landscape heterogeneity gradient. Our objectives were to assess how landscape composition and landscape diversity affect functional traits (ITD and body mass) of species-specific parasitoid, and individual body size for its impact on biological control. From a total of 5002 sampled individuals of the three parasitoids, regression analysis revealed that (1) the presence of water bodies within the landscape respectively positive affected the ITD of E. sinicus and M. russata at 2000 m scales, landscape factors had yet no discernible effects on either the body size (ITD or body mass) of C. chilonis, (2) habitats with high landscape diversity had a negative effect on body size (ITD and body mass) of the solitary parasitoids E. sinicus at 200 m scales, and (3) a significantly negative correlation was found between the parasitoid emergence rate and ITD of E. sinicus. Our findings suggest that parasitoids’ body sizes may respond differently among species to landscape features. Solitary parasitoids in our study were more sensitive to variation in habitat resource-availability than was the gregarious parasitoid. We conclude that landscape habitat changes can affect the body size and parasitism of parasitoids, modifying their biocontrol services against pests.

Searching of Underground Host Patches by a Pupal Parasitoid.

When hosts are distributed in discrete patches, ways in which parasitoids search and move between patches affect variability in parasitism risk among hosts and host-parasitoid population dynamics. This study examined the patch searching behavior of the solitary pupal parasitoid Dirhinus giffardii (Silvestri) (Hymenoptera: Chalcididae) on its host Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) which pupates underground. In a series of two laboratory experiments, host patches were created by burying pupae in peat moss, and the foraging behavior of the parasitoid was recorded. If D. giffardii can detect underground patches, the parasitoid would preferentially exploit high quality patches where the quality of a patch is represented by the number of unparasitized hosts in the patch. The first experiment investigated the effect of patch size (i.e., number of hosts) and host status (whether hosts are parasitized or unparasitized) on patch searching behavior. Results showed parasitoids were more likely to exploit a large patch than a small patch regardless of host status. The second experiment examined the effect of relative locations of patches by establishing three patches (one large patch and two small patches with unequal inter-patch distances from the large patch). The probability of parasitism was lower for the small patch close to the large patch than the small patch far from the large patch. The parasitism patterns described in the experiments have important implications on the distribution of parasitism risk among hosts and population dynamics.

Rearings of four European Microgastrinae (Hymenoptera: Braconidae), three new to Britain including a new species of Cotesia Cameron, 1891

Cotesia carterocephali sp. nov. is described from a single gregarious brood reared from a posthibernation final instar larva of the hesperiid butterfly Carterocephalus palaemon in Scotland. Details of English rearings of two other Microgastrinae recorded from Britain for the first time are also given: Distatrix pompelon, gregariously from the erebiid lymantriine Orgyia antiqua (also recorded from the same host in Austria), and Dolichogenidea hemerobiellicida, solitarily from the coleophorid Coleophora hemerobiella (with a record from possibly the same host in the Netherlands). The non-British Glyptapanteles aletta is recorded as a solitary parasitoid of Limenitis populi in Finland, France and Germany: a previous host record for this parasitoid is regarded as incorrect.