A Study of the Taxonomic Status of Deinacrida Parva and Deinacrida Rugosa (Orthoptera: Stenopelmatidae), Two Giant Weta from Central New Zealand

Abstract

This work examines whether the two allopatric species of giant weta (Orthoptera: Stenopelmatidae) currently known as Deinacrida rugosa and Deinacrida parva should be reclassified as a single species. Cytogenetics, allozyme electrophoresis, and morphological techniques were used to compare the two 'species' and produce data from which a conclusion could be drawn. Cytogenetically the two species are very similar. Both have a diploid complement of XO = 29, XX = 30, the sex determination system being a single X chromosome in males and two X chromosomes in females. The autosomes of both species are all acrocentric, except in some minority karyotypes. Intraspecific variation was seen in both species. This variation involved the addition of chromosomal material to otherwise acrocentric chromosomes in some karyotypes. The allozyme work showed no variation between any of the weta examined. The taxonomic use of allozyme data in studies involving potential allopatric species is discussed. A number of morphological traits were found that varied between the species. The taxonomic significance of such variation is often unclear. It is concluded that the 'species' Deinacrida parva is not valid, for nomenclatural reasons, and populations currently known as Deinacrida parva should either be named anew or synonymised with Deinacrida rugosa. This study recommends that populations currently known as Deinacrida parva are bast regarded as at least a subspecies of Deinacrida rugosa. The suitability of the methods used in this study for the task of detecting allopatric species is discussed, and all are found wanting to some degree. The determination of allopatric species is more complicated than most workers credit, and techniques not appropriate to it are often used, producing unconvincing results and highly subjective conclusions.