Life cycle, behaviour and conservation of the large endemic weevil, Hadramphus spinipennis on the Chatham Islands, New Zealand

Populations of the endangered weevil Hadramphus spinipennis (Coleoptera: Cu rculionidae), endemic to the New Zealand Chatham Is, were sampled five time s from December 1993 to January 1997. All stages of its life cycle were clo sely associated with its host plant, the Chatham Is. endemic Aciphylla dief fenbachii (Apiaceae). Adult weevils were found throughout the year, predomi nantly on male A. dieffenbachii plants where they fed on foliage and flower s. Copulation took place from September to March, mostly on male flowers. E ggs were laid in the soil under host plants from September to April/May. Th e five larval instars fed on the roots, and pupation took place in the soil . In shadehouse studies, the shortest period from neonate to pupa was 147 d ays and pupation took less than 30 days. Field and laboratory data suggeste d that eggs laid early in spring developed into adults by early autumn, but that those laid in late summer overwintered as larvae and pupated the foll owing spring. There is one extended generation a year. Occasionally, adult weevils could also be found on Pseudopanax chathamicum, but clearly preferr ed A. dieffenbachii in 'choice feeding tests'. No larvae were found on the roots of P. chathamicum. To secure the long-term survival of H. spinipennis , a third viable population is considered necessary. We suggest a survey of other islands for Hadramphus and/or the establishment of a third populatio n.