Agents for biological control of novel hosts: assessing an aleocharine parasitoid of dung-breeding flies.
Host acceptance and suitability of a range of dipterous hosts of the predator/parasitoid Aleochara sp. were studied in South Africa to assess the likelihood of the parasitoid attacking the novel target pest Haematobia irritans exigua in Australia. In laboratory experiments, 1st-instar parasitoids were presented with puparia of H. thirouxi potans and other candidate host species in choice and no-choice tests. Parasitized puparia were reared to determine survival and parasitoid size. Some species were not acceptable as hosts. The parasitoid larvae were apparently attracted to, but could not penetrate the puparium of Musca xanthomelas. They penetrated, but did not feed on, M. sorbens and died in the 1st instar. The remaining hosts tested, Borborillus marginatus, Sepsis thoracica, H. thirouxi potans, M. domestica and Orthellia peronii [Neomyia peronii], were penetrated and consumed, with resulting development to a range of parasitoid sizes and with variable survival rates. The relationship between a preference index and the log10 of host mass was quadratic, with preference relative to H. thirouxi potans increasing with increasing host mass up to 8 mg and decreasing thereafter. Parasitoid mass increased but survival decreased with increasing host mass. From the size of field-collected Aleochara sp., the relationships determined in the laboratory, and the ecology and mass of H. irritans exigua in Australia, it is considered likely that Aleochara sp. would accept and develop successfully on the target species in Australia.