Implications of host weevil circadian activity for parasitism by Microctonus aethiopoides (Hymenoptera: Braconidae)

Abstract

Previous studies have suggested that the braconid parasitoid Microctonus aethiopoides Loan oviposits in its target host Sitona discoideus (Kuschel) primarily during light periods, and therefore, diurnally active non-target weevils may be more susceptible to parasitism than nocturnally active weevils. A laboratory investigation was carried out to measure the circadian feeding and oviposition activity patterns of three known non-target hosts of M. aethiopoides. M. aethiopoides was also exposed to Listronotus bonariensis Gyllenhal, a crepuscularly active weevil, in light or dark periods or continuously over a 16 hour light: 8 hour dark photoperiod. Feeding by two native species increased during the light period, while that of the introduced Rhinocyllus conicus (Froelich) remained relatively constant throughout the light-dark cycle. Neither of the native species showed a consistent circadian oviposition pattern. R. conicus laid more eggs during light than dark periods. M. aethiopoides oviposited in L. bonariensis equally during light and dark periods.