Monograph of the Monistriini and Petasidini (Orthoptera : Pyrogomorphidae)

Abstract

A numerical taxonomic study is made of the endemic Australian tribe Monistriini auct, in relation to the African and Indian Poekilocerini. It is concluded that the genera Petasida and Scutillya are phenetically as removed from the remainder of the Monistriini auct. as the Poekilocerini are from either; a new tribe Petasidini is erected to accommodate them. The two Australian tribes are revised comprehensively, with descriptions, figures, and keys of the 14 species. One new genus, Parastria, with new species P. reticulata, and a new species Monistria consobrina, are recognized. Extensive intraspecific geographical variation is described for most of the species and numerous geographical races discriminated. Distributions are documented by means of detailed maps. Biological information is presented when available. A small percentage of macropterous individuals occurs in several species of the mainly brachypterous genus Monistria; evidence is presented for regarding these as in part a kentromorphic phenomenon, but gregariousness has not been observed. Any one species has a limited range of host plants, many of which contain toxins. It is suggested that these are sequestered in the haemolymph as a defence against diurnal vertebrate predators and advertized by the usually aposematic coloration. An origin of the two Australian tribes from a common ancestor with the Poekilocerini is hypothesized for the Cretaceous period, throughout most of which Western Australia and India were in contact or near-contact. A 'lenticular organ' observed on the antennae of all the species has been found to occur widely in the Acridoidea.