Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology

Biomechanical properties of insects in relation to insectivory: cuticle thickness as an indicator of insect ‘hardness’ and ‘intractability’

Alistair R. Evans A B C and Gordon D. Sanson A
+ Author Affiliations
- Author Affiliations

A School of Biological Sciences, Monash University, Clayton, Vic. 3800, Australia.

B Current address: Institute of Biotechnology, PO Box 56 (Viikinkaari 9), University of Helsinki, FIN-00014 Finland.

C Corresponding author. Email:

Australian Journal of Zoology 53(1) 9-19
Submitted: 10 March 2004  Accepted: 5 November 2004   Published: 24 February 2005


The concept of ‘hardness’ has long been used to describe the biomechanical properties of the diet of many animals. However, due to the lack of a consistent definition, and the multitude of uses to which the term has been put, the use of the term ‘intractability’ has been advocated here to represent the extent to which the structural strength, stiffness and toughness are increased in a foodstuff. The thickness of the cuticle of an insect was a good measure of the intractability of cuticle. The tremendous advantage of the use of cuticle thickness as a measure of the biomechanical properties of invertebrates means that the dietary properties of a living insectivore can be directly quantified according to the thickness of the cuticle in its faeces. The quantitative measurement of intractability obtained through this technique can be used in correlations with adaptations of the masticatory apparatus, including tooth and skull morphology, as well as more general considerations of ecology. This is a major advance on previous measures of the biomechanical properties of insectivore diets, and may represent the best technique of any dietary group in assessing the properties of its diet.


Thanks to Lindy Lumsden for sharing her expertise in bat trapping and on general aspects of bat biology, and to two anonymous referees for helpful comments that improved the manuscript.


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