Study of larvae of 12 species of the genus Argas showed that chaetotaxy in conjonction with other features affords useful diagnostic characters for subgeneric and species identification. Chaetotaxic features that had the greatest value were the number, arrangement and length of setae on the body, palpi and leg segments. In addition to chaetotaxy, features such as the shape and dentition of the hypostome,length of the palpal articles, shape and length of tarsus I, as well as host preference and distribution, were found to provide useful recognition characters. A key is provided to demonstrate the practical use of these features.