The number of larval instars in the flax weevil (Anagotus fairburni) (Coleoptera: Curculionidae)

Brockelsby, WD
Miskelly, CM
Glare, Travis
Minor, MA
Journal Article
Fields of Research
ANZSRC::310302 Community ecology (excl. invasive species ecology) , ANZSRC::310307 Population ecology , ANZSRC::310913 Invertebrate biology , ANZSRC::401105 Life cycle assessment and industrial ecology , ANZSRC::3109 Zoology
The flax weevil Anagotus fairburni is a large flightless beetle, that is one of the members of the endemic insect ‘megafauna’ of New Zealand. It is a protected species that currently persists only on predator-free islands or in remote and difficult to access alpine areas. Little is documented about the ecology of the flax weevil. In this study we estimated the number of instars in the A. fairburni life cycle by measuring the head capsule widths of larvae collected in the field on Mana Island Scientific Reserve. We used kernel density function estimates to predict average head-capsule widths and the number of larval instars. We then used Brooks-Dyar’s law on the head capsule width data and analysed Brooks and Crosby indexes to refine the estimated number of instars based on imperfect data. Results from sampling of 86 larvae suggested four instar groupings, but further analysis based on Brooks-Dyar’s law found that A. fairburni likely passes through 6 or 7 larval stages prior to pupation, with some uncertainty for smaller instars. Our method provides new data on ecology of an endemic species and provides a framework for further work on similar endangered species where data is imperfect or difficult to gather.
© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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