No. 9 — The Ixodes rasus Group of African Ticks with Descriptions of Four New Species (Ixodoidea, Ixodidae) By Don R. Arthur x and Colin Burrow INTRODUCTION Hitherto the African ticks of the genus Ixodes which possess closed circular anal grooves have been incompletely investigated and all such ticks have been referred to the species Ixodes rasus Neumann 1899. This approach to the diagnoses of these ticks was established by Nuttall, Warburton, Cooper and Robinson (1911) and used indiscriminately until Schulze (1943) sub-divided rasus into three subspecies (see later). Consequently, at the present time the status of rasus and other forms as yet undescribed presents an interesting problem to the systematist. This uncertainty of structure, coupled with our ignorance of the biology of the rasus group, opens up a particularly interesting and virgin field for research, and not a few unknown allied species undoubtedly await discovery. Nuttall (1911) classified I. rasus in the biological group within the genus Ixodes in which males and females coexist together on a host that either wanders or does not travel far and in the subgroup where the sexes are found in copula on the host. Even so, the published reports show that the host range of the adults of the I. rasus group varies from small insectivores (mice, ele-phant shrews) to leopards, large antelopes, domestic dogs and man. The picture for immature stage-host relationships is more uncertain. Specimens on which this report is based were obtained from Dr. H. Hoogstraal, NAMRU-3, Cairo, Egypt; Dr. Gertrud Theiler, Onderstepoort Veterinary Research Department; The Museum of Comparative Zoology (through the courtesy of Dr. J. Be-quaert) ; Musee Royal du Congo Beige (through the courtesy of Dr. E. Dartevelle) ; Dr. Pierre Morel, Laboratoire Federal de l'Elevage George Curasson, Dakar, Senegal; Rocky Mountain i The opinions and statements contained herein are the private ones of the Writers and are not to be construed as official or reflecting the views of the Navy Department or the Naval Service at large.