BIOLOGY OF PSEUDOHETERONYX SP (COLEOPTERA, SCARABAEIDAE) ON THE CENTRAL HIGHLANDS AT QUEENSLAND

The life cycle, development rates, fecundity and survivorship of Pseud oheteronyx sp. were studied in the laboratory and field. Adults fed on leaves of Asteraceae (sunflower and Parthenium hysterophorus L., an i ntroduced weed). Larvae in the soil fed on cereal roots and on crop re sidues but developed faster on living wheat roots compared to wheat st ubble. The shortest development time for larvae was 8 months under lab oratory conditions. Teneral adults appeared in the field at the start of the summer wet season (usually December). Sex ratio was 1:1. Size c ould not be used to separate the sexes, which were morphologically sim ilar. Adults began laying eggs about 8 weeks after adult emergence. Un der moist soil conditions in the laboratory, adults laid eggs for 1 ye ar except during 4-6 weeks in winter when mean monthly temperature dro pped below 20-degrees-C. When confined in groups of up to 20 adults, P seudoheteronyx sp. laid an average 18.5 eggs per female when fed sunfl ower leaves, and 3.0 eggs per female when fed leaves of Parthenium. In dividually confined females fed sunflower leaves laid 10-51 eggs durin g their life. Natural enemies recorded in the field included fungal pa thogens (Metarhizium, Beauveria, Hirsutella and Cordyceps spp.) and mi lky disease (Bacillus popilliae).