Spatial and temporal variation in the parasitoid assemblage of an exophytic polyphagous caterpillar

Abstract

1. Over 3400 larvae of the polyphagous ground dwelling arctiid Grammia geneura were sampled and reared over seven generations in order to characterise its parasitoid assemblage and examine how and why this assemblage varies over time and space at a variety of scales. 2. The total parasitoid assemblage of 14 species was dominated both in diversity and frequency by relatively polyphagous tachinid flies. 3. Both the composition of the parasitoid assemblage and frequency of parasitism varied strikingly among and within sampling sites, seasons, and years. 4. Overall rates of parasitism increased consistently over the duration of caterpillar development. 5. Within sampling sites, parasitism rates were non-random with respect to habitat structure and caterpillar behaviour for the most abundant parasitoid species. 6. The large variability in parasitoid assemblage structure over space and time in this system may be a function of local host population abundance, habitat-specific parasitism, and indirect interactions between G. geneura and other Macrolepidoptera through shared oligophagous and polyphagous parasitoids.