New Zealand Journal of Zoology abstracts
Phenology of native weevils (Coleoptera: Curculionidae) in New Zealand
pastures and parasitism by the introduced braconid, Microctonus aethiopoides
Loan (Hymenoptera: Braconidae)
B. I. P. BARRATT
C. M. FERGUSON
A. A. EVANS*
New Zealand Pastoral Agriculture Research
Institute Ltd.
Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand
M. R. MCNEILL
New Zealand Pastoral Agriculture Research
Institute Ltd.
Canterbury Agriculture and Science Centre
P.O. Box 60
Lincoln, New Zealand
P. J. ADDISON
New Zealand Pastoral Agriculture Research
Institute Ltd.
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand
*Present address: School of Veterinary Sciences, Massey
University, Palmerston North, New Zealand.
Abstract The phenology of native brachycerine weevil species
at seven pasture sites in Otago, Canterbury and Waikato was studied by regular
quantitative sampling of adults. Weevils were identified to species, and
dissected to record reproductive status and parasitism by introduced braconid
parasitoids in the genus Microctonus. Climatic data assisted in the
interpretation of some population density patterns. Weevil population density
was estimated for periods of two to five years at the selected sites. Species
in the Entimini (species of Irenimus and Nicaeana) were generally
univoltine, with adults emerging in winter-spring. The main period of
reproductive activity was spring, and parasitism by Microctonus
aethiopoides reached its highest incidence in January. Low level parasitism
of native weevil species by M. aethiopoides was detected at all sites,
and by M. hyperodae at two sites. At one site in Otago, parasitism by
M. aethiopoides was higher and could have affected the population
density of Irenimus aemulator (Broun) and Nicaeana sp. Most
parasitism occurred after the main reproductive period of weevils in spring,
but a putative second generation in some species might be more affected by
parasitoid attack. A native rhytirhinine species, Steriphus variabilis,
differed from the entimines because adults emerged in autumn and spring, and
may be bivoltine. Mechanisms of M. aethiopoides parasitism of non-target
species in the field are discussed.
Keywords Curculionidae; Brachycerinae; weevil phenology;
non-target parasitism; Microctonus aethiopoides; Microctonus
hyperodae
Z99025
Received 7 July 1999; accepted 17 December 1999
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