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

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.