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Does Anti-parasitoid Defense Influence Host-plant Selection by a Generalist Caterpillar?
  • M. S. Singer
  • John O. Stireman, III, Wright State University - Main Campus
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While studies of tri-trophic interactions have uncovered a variety of mechanisms influencing the dietary specialization of insect herbivores, such studies have neglected host-plant selection by generalists. Here, we report an initial investigation on how host-plant quality and a tachinid parasitoid interact to affect the survival and host-plant selection by a polyphagous herbivore. This herbivore, Grammia geneura(Strecker) (Lepidoptera: Arctiidae), is a food-mixing caterpillar that feeds preferentially on forbs. A previous study suggested that G. geneura might eat certain host species for reasons other than benefits of physiological utilization. We hypothesized that host-plant mediated defenses could act against parasitoids, the major mortality agents of late instar G. geneura . Field observations indicated that caterpillars sometimes survived an attack by the parasitoid Exorista mella Walker (Diptera: Tachinidae) in nature. Laboratory experiments showed that the survival of parasitized caterpillars increased on acceptable but nutritionally inferior host-plant species, indicating that anti-parasitoid defense may explain host-plant selection in this dietary generalist. We found no indication that host-plant selection changed according to the parasitism status of individual caterpillars.

Citation Information
M. S. Singer and John O. Stireman. "Does Anti-parasitoid Defense Influence Host-plant Selection by a Generalist Caterpillar?" Oikos Vol. 100 Iss. 3 (2003) p. 554 - 562 ISSN: 0030-1299
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