New Zealand Journal of Zoology abstracts
Development of the willow sawfly, Nematus oligospilus, at different
temperatures, and an estimation of voltinism throughout New Zealand
J. G. CHARLES
D. J. ALLAN
The Horticulture and Food Research Institute
of New Zealand Ltd
Private Bag 92 169
Auckland, New Zealand
Abstract Cohorts of willow sawfly (
Nematus
oligospilus) were reared in the laboratory on crack willow (
Salix
fragilis) at seven constant temperatures between 11.3 and 28.8deg.C. Larvae
developed through 5-7 instars. Body size (length) of adult females was
influenced by temperature and was strongly correlated with fecundity
(R
2 = 0.8973). The developmental threshold (to), determined through
linear regression, was calculated to be 8.1deg.C, and the thermal accumulation
above to required to complete one generation was 321 degree-days. The number of
degree-days available for seasonal development of the sawfly at 10 sites
throughout New Zealand was calculated. Allowing for the period of diapause, it
was estimated that
N. oligospilus might potentially develop through up
to seven generations per year in the North Island and three generations per
year in the south of the South Island.
Keywords Nematus oligospilus; developmental threshold;
seasonal development; diapause; generations
Z99047
Received 16 November 1999; accepted 31 March 2000
PDF file of entire paper: medium quality (331K); (scanned from paper original: notes about this process)
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