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Figures 297 and 298, d", dorsal and ventral views Figures 299 and 300, Q, dorsal and ventral views

Sudan Specimens

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(Figures 297 to 300)



l Torit Thryonomys gregorianus subsp. Feb 2 5 Yei Wmarsh Tatn Feb (SGC)

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.


R. simpsoni has been reported from widely scattered localities thro:#rica within the Ethiopian Faunal Region and probably occurs wherever its favorite host, the cane rat, does. It is common 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 IS27C.TBSquaert 1931).

EAST AFRICA: SUDAN (Hoogstraal 1954B).

KENYA (Common on lesser cane rats, Choeromys £ gregorianus, at Subukia, Nakuru District, 6400 ft. alt.; Hoogstraal legit). UGANDA (Mettam 1935. 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 Días T952C). UNION OF SOUTH AFRICA (Bedford 1936. Theiler 1947).


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,

# # specimens from this host from Uganda, A. D. raser 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. # is closely related to R. simus, this latter species is seldom found on cane rats.




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 lon but who subsequently (1952G,H) recognized the obvious # of R.


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 # been seen, (E. T. M. Reid #: 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.


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 obsolete, shallow, scutal punctations; distinct lateral and posterior grooves; short, converging cervical pits; pearshaped 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 distinguishes 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 3Ol and 302, d', dorsal and ventral views Figures 303 and 304, Q, dorsal and ventral views


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