Parasitic Hymenoptera

Unlike parasitoids of other insect orders that have host-seeking larvae, most parasitic hymenoptera lay their eggs on, in, or very close to a host individual [11]. This requires the adult female to find a suitable host, often with the aid of chemical cues from host frass, pheromones, plant volatiles emitted upon host feeding or egg-deposition, silk, honeydew and other secretions. She may then chemically mark the host following oviposition to reduce superparasitism by herself or intra- and inter-specific insects [11]. 

Parasitic hymenoptera hold promise in integrated pest management schemes, because they parasitize many economically important insect pests in a species-and stage-selective manner. The pheromones and kairomones of the parasitic hymenoptera have been studied for a long time, and there are many examples where there is evidence of chemical mediation of parasitoid behavior. This review emphasizes work done since the last major reviews [11, 12, 42] and, where it is available, on the primary bioassay-guided chemical identification of the semiochemical (Fig. 2 and Tables 3 and 4). 

Fig. 2 Structures of recently identified semiochemicals of parasitic hymenoptera...

Table 3 Recently identified sex pheromones of parasitic hymenoptera. Numbers in bold refer to chemical structures shown in Fig. 2...

In Alloxysta victrix, 6-methylhept-5-en-2-one 16, which is produced by both males and females, was identified as potentially attractive to the males and slightly repellent to the females in Y-tube olfactometer assays [60]. In this study, the activity was also dependent on prior exposure of the insects to the compound. Naive insects responded more strongly than previously exposed ones. This underscores a second difficulty in the bioassay-guided identification of parasitoid hymenopteran pheromones the responses are very dependent on the context and on prior exposure. Learning has been demonstrated in several species of parasitic hymenoptera [61-65]. 

Parasitic hymenoptera often eavesdrop on the pheromone communication of their host species. The type of host pheromone recognized depends on the host stage parasitized. Phoretic egg parasitoids are often attracted by the host sex pheromone, while species that parasitize later stages (larval, pupal) often do not respond to host sex pheromone components [ 11,42]. Larval parasitoids often recognize volatiles from the damaged host plant and/or host larval frass volatiles. Parasitoids of forest beetles respond to the beetle aggregation pheromones [42]. 

Nuclei of the fat body are the principal site of replication of subgroup C baculoviruses. Subgroup D baculoviruses replicate In nuclei of calyx epithelial cells, In the ovaries of parasitic Hymenoptera. 

Carpenter, J.M. (1997). Phylogenetic relationships among European Polistes and the evolution of social parasitism (Hymenoptera Vespidae Polistinae). In The Origin of Biodiversity in Insects Phylogenetic Tests of Evolutionary scenarios, ed. P. Grandcolas. Mem. Mus. Nam. Hist. Nat. 173, pp. 135-161. 

Host-Regulating Factors Associated with Parasitic Hymenoptera... 

Many factors contribute to the interactions of parasitoids and their host insects (10). Table I summarizes data of parasitic Hymenoptera that regulate the biochemistry, development, and behavior of their host. This is an attempt to list those species that have been subjected to thorough studies and is not intended to be a complete list. 

Table I. Parasitic Hymenoptera With Host-Regulating Factors ...

However, several studies have confirmed the application of the hypothesis to parasitic Hymenoptera as well. 

Teratocytes and Serosa. Teratocytes, which originate from the disintegration of an embryonic membrane or serosa (= trophamnion) of some parasitic Hymenoptera, appear to have a significant role in parasitoid-host interactions (, 77-80, Dahlman, D. L. Arch. Insect Biochem. Physiol., in press). A discussion of teratocytes is... 

Secretions from Glands and Other Specialized Tissues. In general, parasitic Hymenoptera are known to inject secretions from glands and specialized tissues into their hosts. Those secretions, except for the symbiotic viruses and virus material or calyx fluid, are collectively presented in the next two sections as venomous substances. 

Q The regulatory factors produced by parasitic Hymenoptera have... 

Flanders, S. E. (1959) Differential host relations of the sexes in parasitic Hymenoptera. Ent, exp. appL, 2, 125-42. 

Hirose, Y. (1979) Behavioral ecology of parasitic Hymenoptera. In Ecological Aspects on Insect Behavior Vol. 4 (Ishii, S., Oashima, C., Tateda, H. and Hidaka, T., eds) pp. 105-49. Barfuukan, Tokyo (in Japanese). 

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