The functional response of Uscana lariophaga under different egg distributions of its host Callosobruchus maculatus.
The functional response of the trichogrammatid egg parasitoid Uscana lariophaga was tested under 3 different host distributions (even, clumped and random) within egg clusters of Callosobruchus maculatus. A Holling Type II functional response was found for all 3 distributions. Over low host densities, less than 50% of the host clusters were parasitized. At low host densities, U. lariophaga females parasitized significantly fewer eggs in random egg clusters with many seeds of cowpea (Vigna unguiculata) than in clusters with fewer seeds and an even or clumped egg distribution. At higher egg densities, plateau levels of maximum number of hosts parasitized were the same for all 3 egg distributions. U. lariophaga appears to be adapted to search for even or clustered egg distributions, as can be found in the field and under storage conditions.