Studies on the histerid beetle Pachylister chinensis in Fiji, and its possible value in the control of buffalo-fly in Australia

Abstract

P. chinensis, a predacious beetle that feeds on dipterous larvae breeding in dung of herbivores, was introduced from Java to Fiji in 1938 for the control of houseflies. The species is confined to areas having a wet tropical climate with a well-distributed annual rainfall exceeding 100 in. The beetle has a marked preference for cow pads in pastures with well-drained soils, and avoids areas shaded by trees. The female lays one or two eggs in the soil beneath a cow pad, and stays there from 2 to 3 days. P. chinensis larvae feed on active maggots as well as on fly puparia. Larval development occupies 16-20 days, and the pupal period some 30 days during the Fijian winter. In Fiji, P. chinensis has at least six generations per annum, and the adults live for more than a year. An abundance of prey ranging in length from 5 to 15 mm is essential for the survival of P. chinensis in Fiji, which attained a mean density ranging up to five beetles per cow pad in some localities. Laboratory tests at this density indicated that, due to the limited searching ability of the beetles and their larvae, only about 30-50 % of maggots in cow pads were destroyed. Because of its irregular density distribution and limited searching ability, no reliance should be placed on this predator for the control of the buffalo-fly in Australia. It is suggested that the efficiency of histerids in controlling flies could be enhanced by the introduction of dung beetles which would substantially reduce the breeding habitat of dipterous pests, thereby making them more vulnerable to predation. The evidence obtained during the course of this study did not suggest that P. chinensis influenced the abundance of houseflies in Fiji.