An analysis of the fate of eggs of Gratiana spadicea (Klug, 1829) (Coleoptera: Chrysomelidae: Cassidinae) in relation to the position in the ootheca

Abstract

Randomly sampled oothecae of a natural population of Gratiana spadicea from the outskirts of Porto Alegre, RS, were dissected. The overlapping of the egg membranes makes possible to enumerate the eggs in a batch and therefore to relate mortality to position in the ootheca. The ootheca of this cassid provides a spatial refuge for some of its eggs. Successful eggs of G. spadicea amounted to less than one fifth of the total in each batch. Parasitoids and predators were responsible for a high mortality of eggs whatever the size of the ootheca. The main cause of mortality was the eulophid wasp Emersonella ooecia De Santis, 1983. A large proportion of eggs were sucked dry by the mirid Tupiocoris cincticornis (Stal, 1860). The sucked eggs could have contained either the embryo of G. spadicea or the parasitoid in the pre-emergence stages.