Abstract
The cassid beetle, Stolas sp., is an abundant leaf-eating herbivore, both as larva and adult, on the vine, Ipomoea asarifolia, a wild relative of the sweet potato. In the region around Manaus (Amazonas State, Brazil), an average of 86% of the egg clutches were completely parasitized by the eulophid, Emersonella neveipes. The wasp is phoretic on female beetles. In comparison with field beetles that lacked phoretic wasps, beetles in association with wasps (1) produced eggs sooner. (2) produced more egg clutches, and (3) had a shorter laboratory life expectancy. Host discrimination by the wasp is probably an active process rather than a passive association with randomly encountered beetles. Emersonella neveipes also attacks Chelymorpha cassidea, a pest of sweet potato. Since Stolas sp. does not, as adults, feed on sweet potato foliage and does not occur in sweet potato fields, it could provide a useful innocuous alternate host for Emersonella neveipes. Since some species in the Convolvulaceae are important weeds in field crops, foliage-feeding cassid beetles may play a useful role in weed suppression. Any biological control program for the suppression of sweet potato pests may favor the spread of those noxious weeds that share the herbivore fauna of sweet potatoes.