Abstract
Regulation of intensity of parasitism in spider-egg parasitoids is more complex than in mast parasites, since spider eggs are tightly packed in sacs and factors controlling proportion of eggs parasitized per sac also regulate population densities. Both microhymenopterans Baeus achaearaneus (Scelionidae) and Tetrastichus sp. (Eulophidae), are egg parasitoids of the spider Achaearanea tepidariorum in Costa Rica. B. achaearaneus tends to locate a large number of sacs and to parasitize only a small proportion of eggs in each; Tetrastichus sp. locates a small proportion of the sacs available (typical of all parasites studied heretofore), but maximizes the utilization of eggs in each sac. The latter is intrinsically superior whenever both species attack the same sac (multiple parasitism).References
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