The defender role of the precocious larvae of<i>Copidosomopsis tanytmemus</i>Caltagirone (Encyrtidae, Hymenoptera)

Abstract

Abstract A specialized larval morph, here called the precocious larvae, is present in broods of the polyembryonic encyrtid wasp, Copidosomopsis tanytmemus Caltagirone, an egg‐larval parasite of the Mediterranean flour moth, Anagasta kuehniella (Zeller). The precocious larvae are clonally derived from the same embryonic cells that produce the normal larvae. In contrast to their normal siblings, precocious larvae have well‐developed cranial structures and mouthparts, and are extremely motile. The most unusual feature of precocous larvae, however, is their failure to attain reproductive age; they invariably die in the host hemolymph as untransformed larvae. Competition experiments with the braconid Phanerotoma flavitestacea Fischer or one of the ichneumonids Venturia canescens (Gravenhorst) and Trathala sp. showed that precocious larvae injured or killed these competitors in 74, 98, and 97%, respectively, of the observed cases of multiple parasitism. Dissection of parasitized host larvae revealed that dead parasite larvae had different fates. Although injured and dead braconid and ichneumonid parasites were encapsulated by aggregations of host lamellocytes, precocious larvae remained unencapsulated, regardless of whether death occurred normally or, rarely, resulted from injury. It is hypothesized that successful avoidance of encapsulation by both precocious and normal larvae of C. tanytmemus is due to either or both of the host‐produced cyst or the parasite‐produced trophic membrane. The precocious larvae fulfill the requirements for the ultimate altruist predicted by kin‐selection theory. However, because they are genetically identical to the individuals whose survival they enhance, the precocious larvae paradoxically qualify as a completely selfish caste as well. It is thus pointed out that the biological role of the precocious larvae is most appropriately evaluated as that of defender.