Biology of Pseudoheteronyx sp. (Coleoptera: Scarabaeidae) on the Central Highlands of Queensland

The life cycle, development rates, fecundity and survivorship of Pseudoheteronyx sp. were studied in the laboratory and field. Adults fed on leaves of Asteraceae (sunflower and Parthenium hysterophorus L., an introduced weed). Larvae in the soil fed on cereal roots and on crop residues but developed faster on living wheat roots compared to wheat stubble. the shortest development time for larvae was 8 months under laboratory conditions. Teneral adults appeared in the field at the start of the summer wet season (usually December). Sex ratio was 1:1. Size could not be used to separate the sexes, which were morphologically similar. Adults began laying eggs about 8 weeks after adult emergence. Under moist soil conditions in the laboratory, adults laid eggs for 1 year except during 4–6 weeks in winter when mean monthly temperature dropped below 20°C. When confined in groups of up to 20 adults, Pseudoheteronyx sp. laid an average 18.5 eggs per female when fed sunflower leaves, and 3.0 eggs per female when fed leaves of Parthenium. Individually confined females fed sunflower leaves laid 10–51 eggs during their life. Natural enemies recorded in the field included fungal pathogens (Metarhizium, Beauveria, Hirsutella and Cordyceps spp.) and milky disease (Bacillus popilliae).