Both species of tick which are described in the present paper are members of insular faunas and demonstrate remarkably well the tendency, shown by these parasites in geographical isolation, to species formation. In this connexion it is perhaps worth quoting what Cooley & Kohls (1945) say concerning this subject in their recent work on the genus Ixodes: ‘These studies’, they write on p. 1 of their introduction, ‘have revealed in considerable measure the more useful specific characters and the importance of a real appreciation of the significance of geographical range and variation in the differentiation of species.… In determination of species limits we have considered not only morphologic but also biologic factors such as host relationships and geographic distribution. No subspecies are recognized.’ There is little doubt but that geographical distribution will be found to play an almost equally important role in the genus Amblyomma.