Parasitoid strategies

Powell, W., Pennacchio, F., Poppy, G. M. and Tremblay, E. (1998). Strategies involved in the location of hosts by the parasitoid Aphidius ervi Haliday (Hymenoptera Braconidae Aphidiinae). Biological Control 11 104-112. 

Figure 9.1. Different defense strategies of Nicotiana plants that evolved in response to herbivore attack. Besides a specialized germination-behavior that efficiently reduces the over-all number of potential herbivores, Nicotiana plants evolved the inducible nicotine synthesis as a direct defense and the inducible emission of volatiles to attract parasitoids of the herbivore as an indirect defense. A specialized defense mechanism is triggered in response to attack by the herbivore Mctduca sexta, adapted to Nicotiana plants. Attack results in an ethylene burst, which down regulates nicotine accumulation and results in a fundamental transcriptional re-organization within the plant.

Vinson, S. B. In Evolutionary Strategies of Parasitoids and Their Hosts Price, P, Ed. Plenum Press New York, 1975 pp 14-48. 

Although the evolutionary strategies of parasitoids, parasites, and phytophagous species may differ, the problems they encounter in the location of ovi-position sites often have many similarities (Vinson, 1981). Upon emergence, a female parasitoid is often in an alien habitat or a habitat devoid of hosts due to the presence of unsuitable host stages or because the host population may have shifted spatially. The problem is more critical if one considers the suggestion of Price (1980) that clumped host populations may be exploited to extinction. 

The strategies used by insects in the host selection process, whether for food or for oviposition sites, may appear superficially to differ, but actually they have a great deal in common. While host selection for most parasitoids involves a single stage (i.e., the adult female) this is not always true. For example, the female tachinid Lixophaga diatraea, deposits eggs near host frass. The larvae must then locate and accept the host (Roth et al., 1978). 

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