Inverse density-dependent and density-independent parasitism in a solitary ground-nesting bee in Southeast Brazil

Aspects of the population dynamics of a solitary ground-nesting oligolectic bee, Diadasina distincta (Holmberg 1903) (Hymenoptera Anthophoridae), were studied in relation to the number of parasitized nests in aggregations of different sizes. Inversely density-dependent parasitism by bombyliid flies and density-independent mortality by fungi together explained most of the variation in population size. There was a significant negative correlation between the number of nests in an aggregation and parasitism by bombyliid flies. Bombyliids accounted for 19.4% of mortality and two fungal species for an additional 19%. It is hypothesized that male patrolling in larger aggregations accounted for lower parasitism rates by bombyliid flies.