Observations on oviposition and host-feeding behavior of Aphelinus gossypii timberlake (Hymenoptera: Aphelinidae)

Abstract

Oviposition and host-feeding behaviors of Aphelinus gossypii were examined, with the aid of a video-recorder, and compared. A total of 139 encounters between female wasps and second-to fourth-instar larvae of Aphis gossypii were observed. Of these encounters 53 led to oviposition and 20 to host-feeding. In ovipositional attacks wasps examined aphids with the antennae, turned backward, everted the ovipositor and inserted it. In feeding attacks, the wasp inserted the ovipositor more deeply than in ovipositional attacks, kept the hind legs on the aphid and repeatedly inserted and withdrew the ovipositor. Then the wasp turned forward, searched the ovipositor wound and fed on the body fluids of the aphid. On 36 occasions wasps failed in ovipositing due to defence reactions by the aphids. Sometimes an egg was deposited but it was not completely placed into the aphid body and shrivelled soon afterward. On 19 occasions wasps were not able to locate the ovipositor wound after turning forward. Two of these wasps attacked the same aphids again but 17 retreated. The mean duration from encounter with an aphid to retreat was 347 s (5.8 min) for oviposition and 1,798 s (27.7 min) for host-feeding.