Host-age effects on oviposition behavior and development of Oomyzus sokolowskii (Hymenoptera: Eulophidae), a larval-pupal parasitoid of Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract

Second-, third-, early and late fourth-stadium larva, and pupa of Plutella xylostella (L.) were singly presented to female Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) in the laboratory to investigate the effects of host age on oviposition behavior and development of the parasitoid. With regard to the oviposition behavior, the following three events were recognized after encountering the host: (1) drumming by antennae, (2) ovipositor penetration and oviposition, and (3) host feeding. Host acceptance rates did not differ among the different host ages except for pupa. Time required for ovipositor penetration and oviposition tended to increase with host age. About one third to one half of the wasps showed host feeding behavior irrespective of host age. The parasitism rate for fourth-stadium host larvae was higher than that for the second- and third-stadia. There were no significant differences among mean development times of the wasp in second-, third-, and early fourth-stadium larvae. However, development times in the late fourth-stadium hosts (=prepupa) were significantly shorter than in the early fourth- and other stadia hosts. This suggests that larval development of O. sokolowskii is influenced by host physiology.