The life history and host-searching behaviour of the aquatic parasitoid wasp Apsilops japonicus (Hymenoptera: Ichneumonidae), a parasitoid of the aquatic moth Neoshoenobia testacealis (Lepidoptera: Crambidae)

Abstract

The life history and host-searching behaviour of Apsilops japonicus parasitizing the aquatic moth Neoshoenobia testacealis were studied in the field and in the laboratory in Japan. Moth larvae initially mine the floating leaves of the yellow water lily, later boring into the petiole and pupating in the petiole underwater. While the wasps did not attack leaf-mining larvae, they were idiobiont ectoparasitoids of the pupae or mature larvae of N. testacealis in the petioles. The wasps did not swim with their wings or legs when searching for hosts underwater, they walked down leaf petioles into the water. It is presumed that the wasps overwinter as adults. The laboratory observations suggested that the female wasps could not detect the host presence in the petiole from the floating leaves and they randomly searched for hosts by probing with their ovipositors underwater.

Keywords:

• aquatic moth
• aquatic wasp
• host-searching behaviour
• parasitoid
• yellow water lily

Acknowledgements

The authors are grateful to T. Endoh, Y. Yoshiyasu, R. Matsumto, K. Maeto, M Ishi and M. Sano for their valuable comments on the study. We also thank G. Broad and anonymous reviewers who improved this manuscript and G. Itoh for her assistance in the field and experimental studies.