Experimental studies of predation on grassland populations of Australian soldier fly, Inopus rubriceps (Macquart) (Diptera: Stratiomyidae)

Abstract

Predation on larvae and pupae of the soldier fly Inopus rubriceps was studied in Southeast Queensland and New Zealand grasslands. Larvae were killed by invertebrate predators when artificially ‘planted’ in the field. Wireworm predation influenced larval survival in New Zealand, but not in Queensland. Pupae were vulnerable to predation in both countries. A relatively constant proportion (74%) of pupae were killed at each of seven densities between 350 pupae/m² and 10 000 pupae/m² which were planted in grassland. Pupal survival was higher in plots designed to exclude invertebrate predators than in exposed plots. Larval density was subsequently three times higher in predator exclusion plots than exposed plots. Similar trends were indicated in unreplicated large-plot experiments (three in South-eastern Queensland, one in New Zealand) where predator numbers were reduced by insecticide treatment. Predation on pupae and perhaps larvae by invertebrates (probably Carabidae, Staphylinidae and larval Elateridae), influenced the size of the subsequent larval population.

Keywords:

• Australian soldier fly
• Inopus rubriceps
• Stratiomydae
• predation
• grasslands
• Elateridae
• Carabidae
• Staphylinidae
• experimental design