Rationale
Castleton's Flightless Katydid (Austrodontura castletoni) is Critically Endangered under criteria B1 and B2 because it has a small area of occupancy and extent of occurrence (8 km2 each), has been found only at two localities, has a severely fragmented distribution, and its area, extent and quality of habitat are estimated to be in decline. This species occurs only within Silaka Nature Reserve, Eastern Cape, South Africa, within the Indian Ocean Coastal Belt indigenous forest biome, a habitat type which is severely fragmented. Due to its highly restricted distribution even a small disturbance can have a detrimental effect on the survival of the species as a whole. The most likely threats to the species are deforestation, land use transformation of its natural habitat, habitat destruction as a result of invasive alien plants, particularly Lantana camara, or change in microclimate or distribution of the species' food plants as a result of climate change. Due to its small body size and low motility, this species cannot be expected to shift its range in response to changes in its habitat.