Oncopera

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.

Abstract: Field observations were made on the mating and oviposition behaviour of the hepialid moths, Oncopera alboguttata, O. rufobrunnea and O. tindalei. The three species, which are pasture pests in the New England district of New South Wales, have superficially similar behaviour patterns but a number of differences were observed. In particular, the behaviour of O. alboguttata differs from that of the other two species in several respects. The behaviour patterns of the three species are compared with those of O. intricata and O. fasciculata which have been studied by other workers.

Abstract: In South Australia the underground grass caterpillar, Oncopera fasciculata (Walker), is found only in the higher rainfall area in the south-eastern portion of the State. It appears that the distribution and numbers of this pest of improved pastures are mainly restricted by unfavourable weather (dry and hot) during the egg and early larval stages (late spring-early summer). These stages, as well as older larvae established in subterranean burrows, stand a better chance to survive the dryness and heat where the surface of the ground is covered with dense herbage. Unfed, first-instar larvae are much more susceptible to loss of water than are the eggs. Larvae remain virtually dormant during the summer, but from about April onwards they grow rapidly. The resumption of active feeding and growth is associated with the first substantial autumn rains. During autumn, when the rainfall may be intermittent, the larvae feed more actively during wet periods and become relatively inactive again during dry periods. The relative humidity of the air at the base of a subterranean burrow where the larvae lives was usually above 95 per cent., even when the relative humidity of the air just above the mouth of the burrow was as low as 65 per cent. No measurements were taken during the height of the summer, when the burrows may have been drier than this.

Abstract: Notes on distribution, burrow type, food, laboratory rearing methods, length of the prepupal (last non-feeding larval instar) and pupal stages, and times of emergence of the adults from the pupae are given. Descriptions and/or illustrations of all life stages except the egg are presented. The relationship of Oncopera parva to O. argentata Tindale and O. brachyphylla Turner is discussed and it is concluded that O. argentata is a form of O. parva. O. parva and O. brachyphylla are closely related and O. brachyphylla should therefore be retained in the genus Oncopera Walker, even though it lacks the hind tibial hair-tuft in the male.