New Zealand Journal of Zoology abstracts
Life cycle, behaviour and conservation of the large endemic weevil,
Hadramphus spinipennis on the Chatham Islands, New Zealand
K. SCHÖPS*
S. D. WRATTEN
R. M. EMBERSON
Division of Plant, Soil and Ecological Sciences
P.O. Box 84
Lincoln University
Canterbury, New Zealand
*Present address: University of Helsinki, Department of Ecology and
Systematics, Division of Population Biology, P.O. Box 17, FIN 00014 University
of Helsinki, Finland
Abstract Populations of the endangered weevil Hadramphus
spinipennis (Coleoptera: Curculionidae), endemic to the New Zealand Chatham
Is, were sampled five times from December 1993 to January 1997. All
stages of its life cycle were closely associated with its host plant, the
Chatham Is. endemic Aciphylla dieffenbachii (Apiaceae). Adult weevils
were found throughout the year, predominantly on male A. dieffenbachii
plants where they fed on foliage and flowers. Copulation took place from
September to March, mostly on male flowers. Eggs were laid in the soil under
host plants from September to April/May. The 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 days and pupation took less than 30 days.
Field and laboratory data suggested 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 following spring. There is one extended generation a
year. Occasionally, adult weevils could also be found on Pseudopanax
chathamicum, but clearly preferred 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 population.
Keywords Hadramphus spinipennis; Aciphylla
dieffenbachii; Chatham Islands.; life history; phenology; behaviour;
conservation
Z98011
Received 10 March 1998; accepted 24 September 1998
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