Density-Dependent Parasitism by a Eulophid Parasitoid: Tests of an Intragenerational Hypothesis

Abstract

I studied intragenerational host location and parasitism rates by Melittobia sp. C, a eulophid parasitoid, whose larvae feed on larvae of Trypargilum politum, a mud dauber wasp. My field and laboratory experiments suggest that host finding by Melittobia is not affected by their host's density in nature. Correlations between Melittobia's cumulative parasitism rate and their host's density have been observed by others. The hypothesis that Melittobia reproduce and increase in abundance more rapidly in a host patch than their host remains to be tested. The dispersion of Melittobia in laboratory experiments suggests that the mud walls of the host's nest limit the number of nests a female Melittohia can search for a host. In spite of this, Melittobia sometimes enter empty nests. Olfactometer experiments provided no evidence that Melittobia use chemical cues to locate their hosts. Melittobia