One of the strongest patterns in the historical record of biological control is that programmes targeted against lepidopteran pests have been far less successful than those targeted against homopteran pests. Despite fueling considerable interest in the theory of host–parasitoid interactions, biological control has few unifying principles and no theoretical basis for understanding the differential pattern of success against these two pest groups.
Himalayan thar or tahr (Hemitragus jemlahicus), Alpine chamois (Rupicapra rupicapra) and brushtail possums (Trichosurus vulpecula) are native to the Himalaya, Europe and Australia, respectively, but are now sympatric in parts of the central Southern Alps, New Zealand. All three species are managed as pests by the Department of Conservation. We analysed the diets of 246 thar, 78 chamois and 113 possums collected in the central Southern Alps during 1988–1996.