Research into the status and distribution of Chatham Islands endangered invertebrates

Abstract

Examination of public collections in New Zealand has established the former distribution of three protected beetle species, the Chatham Islands click beetle (Amychus candezei Pascoe), the coxella weevil (Hadramphus spinipennis Broun), and the Pitt Island longhorn beetle (Xylotoles costatus Pascoe). It has shown that there has been a significant contraction in the distribution of all species to the outer predator-free islands of the Chathams group. A field expedition in November and December 1992 was successful in locating all three species and extending the known distribution of A. candezei to Mangere Island. However, only a single specimen of X. costatus was found. One of the main findings of the expedition was the contrast in diversity and abundance of the ground-dwelling insect fauna between the predator-free islands and Chatham and Pitt Islands. This demonstrates what has already been lost from the larger islands of the group and the extent of the problem facing the Pitt Island restoration project.