Extensive chromosome variation in the stick insect genus Sipyloidea Brunner von Wattenwyl (Phylliidae : Necrosciinae) within Australia, and descriptions of three new species

Abstract

Combined cytological and morphological analyses of stick insects belonging to the genus Sipyloidea Brunner from a limited geographical area in southern and south-western Australia serve to identify three new species, designated as the Nelida group. All three live on species of Acacia and are nocturnal, with micropterous females but fully winged males. Bisexual members of S. nelida, sp. nov., are characterised by 2n = 37 male XO, 38 female XX, but females with counts of 58 XX, 57 XX and 69 XX, 68 XX have been identified within the species. A second species, S. similis, sp. nov., has bisexual forms with 2n = 35 male XO, 36 female XX, as well as females with counts of 58 XX or 57 XX. In both species the females with the higher chromosome counts are capable of parthenogenetic reproduction. Both deposit their eggs under the bark of host plants and shortly after oviposition these liberate a ring of stellate hairs around the opercular region of the egg. The third species, S. ovabdita, sp. nov., is apparently purely bisexual with 2n = 35 male XO, 36 female XX. It is distinctive in its morphological characteristics from both S. nelida and S. similis and lays its eggs in soil, lacking the opercular ring of hairs which characterises the other two species.