To assess the spatiotemporal distribution of insects in a flat storage containing wheat (Triticum spp.), probe traps were suspended in the wheat bulk and inspected for captured insects at 15-d intervals, from June 2001 to August 2002. The grain bulk was 1 m in height, and traps were placed at the upper and the lower 0.5 m of the bulk. During the entire trapping period, 17 insect taxa were recorded. The most abundant species were Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and its larval parasitoids Harbobracon hebetor (Say) (Hymenoptera: Braconidae) and Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae). Most individuals were found in the upper bulk part. The highest E. kuehniella trap catches were found between August and November 2001 and during June and July 2002. Of the two parasitoids, H. hebetor was more abundant than V. canescens, with the exception of winter and early spring, when both species occurred at low numbers, especially H. hebetor. Spatial analysis by distance indices (SADIE) spatiotemporal analysis showed significant clustering of species, especially during summer and autumn. Early in the season and during spring 2002, at low host numbers, V. canescens occupied the locations where E. kuehniella mainly aggregated, but with the increase of E. kuehniella population, H. hebetor occupied these host groups and replaced V. canescens. Although the two parasitoids competed for the same host species, both species coexisted in the storage facility during the entire trapping period.
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Vol. 99 • No. 6