These records, from the east and west banks of Equatoria Province, are the only ones of this species from the Sudan. The Yei specimens in Sudan Government Collections were collected in 1911 by H. H. King, who had identified them as R. simus. DISTRIBUTION R. simpsoni has been reported from widely scattered localities throughout Africa within the Ethiopian Faunal Region and probably occurs wherever its favorite host, the cane rat, does. It is com mon in Kenya and Uganda although it has not previously been reported from Kenya. WEST AFRICA: NIGERIA (Nuttall 1910. Simpson 1912B. Rageau 1953B). CENTRAL AFRICA: CAMEROONS (Rageau 1953A,B). BELGIAN CONGO (Schwetz 1927. Bequaert 1931). EAST AFRICA: SUDAN (Hoogstraal 1954B). KENYA (Common on lesser cane rats, Choeromys g. gregorianus, at Subukia, Nakuru District, 6400 ft. alt.; Hoogstraal legit). UGANDA (Mettam 1935. Bedford 1936. Bedford 1936. Theiler 1947. Numerous specimens seen in collections of Uganda Veterinary Service. See HOSTS below). TANGANYIKA (Reichenow 1941B). SOUTHERN AFRICA: NYASALAND (Wilson 1950B). MOZAMBIQUE (Santos Dias 1952G). UNION OF SOUTH AFRICA (Bedford 1936. Theiler 1947). HOSTS R. simpsoni has been reported only from cane (or "edible") rats, Thryonomys (= Aulacodus) spp. and Choeromys spp. (all authors). What appears to be an exceptional host is the giant forest rat, Cricetomys gambianus; specimens from this host from Uganda, A. D. Fraser legit, are in British Museum (Natural History) collections. BIOLOGY R. simpsoni appears to be almost entirely restricted to cane rats. The paucity of records is possibly due to rarity of host examination. Present evidence would indicate that this is one of the most host-specific of rhipicephalid ticks. Although R. simpsoni is closely related to R. simus, this latter species is seldom found on cane rats. Unstudied. DISEASE RELATIONS REMARKS Adults were figured and redescribed by Theiler (1947). The nymph was described by Santos Dias (1952G), who, incidentally, considered this species as a synonym of R. simus longus but who subsequently (1952G,H) recognized the obvious validity of R. simpsoni. Generally one may be suspicious that records of R. simus from cane rats actually refer to R. simpsoni, although two males of R. simus from a cane rat near Yirol have been seen, (E. T. M. Reid legit). All other collections, labelled as R. simus from cane rats, that have been studied by the writer from various parts of Africa have proven to be R. simpsoni. IDENTIFICATION Male: Size is usually small, from 2.3 mm. to 3.6 mm. long and from 1.5 mm. to 2.2 mm. wide. Typical males are easily distinguished within the R. simus group by a combination of characters including broadly sickleshaped adanal shields; sparse, almost ob solete, shallow, scutal punctations; distinct lateral and posterior grooves; short, converging cervical pits; pear shaped body; and slight dorsal process of coxa I. The several fairly large series of specimens in the present collection and other East African series that have been studied show considerable variation among individuals, though always one or more of the distinctive features of the species are retained. The posterior grooves may be very faint. In small, weak specimens the lateral grooves may be more shallow than usual or they may be indicated by only a row of punctations. In specimens with exceedingly small adanal shields, the characteristic sickleshape is frequently reduced. The pointed dorsal projection of coxa I is very small and in a number of specimens it is reduced to merely a blunt hump. Female: This sex averages 3.4 mm. long and 2.0 mm. wide; it ranges from 2.5 mm. to 3.4 mm. long and from 1.5 mm. to 2.5 mm. wide. The scutum is about one-fourth longer than wide; its posterior margin is sinuous, with a slight medial protrusion; eyes are pale and flat; lateral grooves almost reach the posterior scutal margin; cervical grooves extend posteriorly for about half the scutal length. Scutal punctations are sparse and superficial; interstitial punctations are usually absent, but some fine ones may be present with a few larger punctations in lateral grooves. The great length of the scutum in relation to its width distin guishes females from those of R. s. simus, R. s. senegalensis, and R. bequaerti. This character is an especially important one in specimens in which interstitial punctation is more apparent than is common for R. simpsoni. Figures 301 and 302, o, dorsal and ventral views Figures 303 and 304, 9, dorsal and ventral views RHIPICEPHALUS SIMUS SIMUS PLATE LXXXIV - 729 Torit 2 Torit 1 Ikoto 1 5 Ikoto 1 Torit 18 6 7 Torit 30 19 18 Torit 1 31 28 Juba Burrows of T. b. benvenuta Lotti Forest Praomys tullbergi sudanensis Arvicanthis niloticus jebelae Nov Nov Nov (2) Dec Apr Nov Dec Dec (6) Dec Feb Jan *Also known as the black pitted tick, the glossy brown tick, and the tailtuft brown tick (cf. Theiler 1952A,B). Canis aureus soudanicus Canis aureus soudanicus |