The Stridulatory Apparatus of New Zealand Wetas in the GenusHemideina(Insecta: Orthoptera: Stenopelmatidae)

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Abstract
Two genera of wetas striduate during leg-kicking behaviour which is thought to be defensive. The stridulatory apparatus of these flightless orthopterans consists of a file on each si.de of the second abdominal tergite that is rubbed by a field of pegs on the inner proximal surface of each hind femur. Examination of a size series of wetas showed that the early instars lack femoral pegs and presumably do not produce sound; they jump away when disturbed rather than display the kicking-stridulatory behaviour seen in adults. The number of file ridges was independent of size in this series. Large air sacs beneath the cuticle are thought to act as a reverberatory device. Detailed descriptions of the stridulatory apparatus are given for eight species of Hemideina. These are classified into three groups. Statistical analysis of file ridge counts revealed significant inter-group differences, as well as differences between species within groups. Because of an overlap in ranges, it was concluded that the number of file ridges would not serve as a useful taxonomic character. The possibility of stridulation being used for intra-specific communication is discussed.