Chemical defense against predation in an insect egg

The larva of the green lacewing (Ceraeochrysa cubana) (Neuroptera, Chrysopi dae) is a natural predator of eggs of Utetheisa ornatrix (Lepidoptera, Arct iidae), a moth that sequesters pyrrolizidine alkaloids from its larval food plant (Fabaceae, Crotalaria spp,), Utetheisa eggs are ordinarily endowed wi th the alkaloid, Alkaloid-free Utetheisa eggs, produced experimentally, are pierced by the larva with its sharp tubular jaws and sucked out. Alkaloid- laden eggs, in contrast, are rejected. When attacking an Utetheisa egg clus ter (numbering on average 20 eggs), the larva subjects it to an inspection process. It prods and/or pierces a small number of eggs ton average two to three) and, if these contain alkaloid, it passes "negative judgement" on th e remainder of the cluster and turns away. Such generalization on the part of the larva makes sense, because the eggs within clusters differ little in alkaloid content. There is, however, considerable between-cluster variatio n in egg alkaloid content, so clusters in nature can be expected to range w idely in palatability, To check each cluster for acceptability must therefo re be adaptive for the larva, just as it must be adaptive for Utetheisa to lay its eggs in large clusters and to apportion alkaloid evenly among eggs of a cluster.