Mate Location and the Onset of Sexual Responsiveness in the Parasitoid Wasp Spalangia endius (Hymenoptera: Pteromalidae)

In some animals, transformation to the adult stage occurs in a hidden location, such as a burrow or a host. Males that can locate hidden females sooner, e.g., before they emerge, may have amating advantage, particularly if the females are ready tomate.Whether males locate pre-emergent females and whether pre-emergent females will mate was examined in the parasitoid wasp Spalangia endiusWalker. S. endius parasitize ßy pupae. A single wasp offspring feeds, pupates, and transforms into an adult within the ßy puparium (an outer shell around the ßy pupa), and males emerge a day or more before females. Whether pre-emergent wasps are ready to mate was examined by dissecting them out of their hosts and presenting them with naturally emerged adults of the opposite sex. Many of the pre-emergent wasps were ready tomate. Nevertheless, males did not distinguish between hosts containing a pre-emergent female versus a pre-emergent male, or even between parasitized and unparasitized hosts. In contrast, males were able to differentiate between hosts from which a female versus amale had recently emerged.Although females are ready tomate before emergence, theremay be little advantage to recognizing and stayingwith a host that contains a pre-emergent female because emergence takes so long, which raises the cost of missed mating opportunities elsewhere.