An ecological study of the pasture scarab Aphodius Howitti hope.

Abstract

The larval stage of Aphodius howitti Hope is a pest of improved and sown pastures in south-eastern Australia. The great increase in pasture improvement and of stocking rates over the past 25-30 years have favoured the development of high numbers of this insect, largely because of its preference for leguminous pasture species, especially subterranean clover (Trifolium subterraneum L.). This paper describes a general study of the life-cycle, behaviour, food, and oviposition site preferences of the species and includes a discussion of the mortality factors likely to be of significance in regulating its numbers. The species has an annual life-cycle. Studies on its biology revealed that adult females lay two distinct batches of eggs. The larger batch (c. 35 eggs) is laid before the female feeds in dung, sometimes even before flight; the smaller (c . 15 eggs), after feeding. The presence of dung is therefore not necessary for the survival of the species which is often found at high densities in ungrazed turf. The factors initiating and influencing flight activity were studied in detail. Initiation is triggered by light of a particular intensity; the time of appearance of beetles in flight can be forecast accurately in relation to the time of sunset. Flights are favoured by high temperature, high soil moisture, and by low wind velocity. Unfed beetles fly upwind towards dung pads. Gravid females execute a circling, exploratory flight; they appear to seek out comparatively bare situations for oviposition and usually enter the soil through small cracks such as are made by germinating clover plants.