Polymorphic Precocious Larvae in the Polyembryonic Parasitoid Copidosomopsis tanytmema (Hymenoptera: Encyrtidae)

Abstract

Polymorphism occurs in the larvae of the encyrtid parasitoid Copidosomopsis tanytmema Caltagirone and includes so-called precocious larvae. Earlier observations suggested that precocious larvae may themselves be polymorphic or that they molt, because they exist concurrently in the same host in two forms separable mainly by size. To determine whether or not these forms (“small” and “large”) represent distinct morphs, precocious larvae were collected from a cohort of parasitized hosts. Precocious larvae obtained from sequential host dissections could be clearly grouped into two morphs based on their development and mandible lengths. Small precocious larvae formed in small numbers early during the differentiation of the embryonic tissue mass (polygerm). They did not molt to become the numerous large precocious larvae that occurred during the later stages of parasitoid development. Large precocious larvae retained the trophic membrane after they had dissociated from the polygerm. We conclude that the precocious larvae of C. tanytmema are polymorphic. The significance of this polymorphism is discussed, particularly in relation to its enhancement of the efficacy of C. tanytmema as a parasitoid.