The Canadian Entomologist (2012) 144, 720-726

Leah Flaherty, Jacques Régnière and Jon Sweeney (2012)
Number of instars and sexual dimorphism of Tetropium fuscum (Coleoptera: Cerambycidae) larvae determined by maximum likelihood
The Canadian Entomologist 144 (5), 720-726
Abstract: Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae) is a Palaearctic wood borer that has been established in Atlantic Canada since at least 1990. Neither the number of instars nor methods for determining the instar of field-collected larvae have been documented for this species. Head-capsule width was measured for 949 T. fuscum larvae in order to determine the number of instars in this species, estimate the mean and variance of head-capsule widths associated with each instar, and identify whether head-capsule width is sexually dimorphic. Head-capsule width data were analysed using maximum likelihood analysis of mixture models and the Brooks-Dyar rule. Our results provide strong support for the existence of six larval instars, with sexually dimorphic head-capsule widths in instars five and six. The probability of misclassifying larvae into instar-specific and sex-specific categories ranged from 0.6% to 12.8%, with the highest probabilities occurring when assigning a sex to fifth-instar and sixth-instar larvae.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Jonathan D. Sweeney, Jacques Regniere

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tetropium fuscum		Canada (east)