A field study on the biology of the underground grass caterpillar, Oncopera Fasciculata (Walker) (Lepidoptera: Hepialidae), in South Australia.

Abstract

This paper describes field studies on the biology and behaviour of Oncopera fasciculata (Walker), an important insect pest of improved pastures in the lower south-east of South Australia and the central and western districts of Victoria. Moths fly at dusk during September-October and mate mainly on upright grasses during these flights. The onset of flights seems to be related to a light stimulus but no correlation could be found from the data collected. Eggs are laid on the ground under pasture, where the female shelters at night and during the day; most eggs are laid within 24 hr after mating. Larvae appear in from 3 to 5 wk and live for a short while in communities at the surface of the ground under silken webbing before building individual vertical tunnels in the soil. Larvae emerge from their tunnels along silken runways to feed on surface growth. Annual grasses and clovers are more susceptible to attack than perennials. Feeding continues from October to July and visible damage appears about May, depending upon seasonal conditions. Prepupae appear in July and pucae during July-September.