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R. com situs, as shmm by Theiler, Walker, and Wiley (1956), is a locally coxmnon East African highland parasite with scattered populations in the highlands of Central Africa and of eastern West Africa. Literature before 1933 refers to it as R. co situs, from 1933 onwards mostl as R. gyeri. See REMARKS below £ Theiler, Walker, and Wiley (1956). '

WES1‘ AFRICA: NIGERIA (Mettam 1950. Unsworth 1949,1952. Gambles I951. Theiler, Walker, and Wiley 1956).

CENTRAL AFRICA: CAMEROONS (Unsworth 1952. Theiler, Walker, and Wiley 1956). BELGIAN CQIGO and RUANDLURUNDI (Bequaert 1930A, B ,l931. Theiler remarks in Santos Dias 194%, p. 170. Hoogstraal 1954C. Theiler and Robinson 1954. Van Vaerenbergh 1954. Theiler, Walker, and Wiley 1956. It seems likely that the "R. cap_e_nsis" of Schoenaers 1951A,B, refers to R. comEsitus). _

EAST AFRICA: SUDAN (Neumann 1897, see DISTRIBUTION IN THE SUDAN a5ve. hoogstraal 1954B. Theiler, Walker, and Wiley 1956).

KENYA (Lewis 1933,1934. Theiler, Walker, and Wiley 1956). UGANDA (WilSOn 1943,1250!-,l952,1953. Theiler, Walker, and Wiley 1956). TANGANYIKA (Donitz 1905. Neumarm 1911. Theiler, Walker, and Wiley 1956. J. B. Walker, unpublished; see nosrs below).

SOUTHERN AFRICA: NORTHERN RHODESIA (Le Roux 1947. Theiler remarks In Santos Dias 1949D, p. 170. Matthysse 1954. Theiler, and Robinson 1951.. Theiler, Walker, and Wiley 1956). NYASALAND (Theiler remarks in Santos Dias l949D. Wilson 1950B. Theiler, Walker, and Wiley 1956). MOZAMBIQUE (Santos Dias 1949A,E,F, l952H,l953B,l954A. Theiler, Walker, and Wiley 1956).


The buffalo appears to be the preferred host of R. comasitus and other larger game animals to be second choice. ti some areas, this tick transfers to cattle but, as shown by Theiler, Walker, and Wiley (1956), it is not known to do so in Kenya. In Northern

Rhodesia, Matthysse (1954), however, recorded this tick only from cattle- A single incidence of parasitism on man has been reported. Hosts of the immature stages in nature are unknown.

yin (Hoogstraal 1951.6).

Domestic animals: Cattle (Neumann 1904,1911, Hilson 191.8,

l950A,§, Santos Dias 1949A,F,l953B. Matthysse 1954. -Van Vaeren. bergh 1951+, Theiler, Walker, and Wiley 1956). Dog (Donitz 1905,

Theiler, Walker, and Riley 1956).

Wild animals: Buffalo (Lewis 1933, Wilson l948,l950B, Santos Dias T9538, Theiler, Walker, and Wiley 1956). Rhinoceros (Lewis 1933 Theiler, Walker, and Wiley 1956). Roan antelope (Lewis 1931.). E].and (Theiler, Walker, and wiley 1956). Lichtenstein's hartebeest (Santos Dias l952H,1953B). Sitatunga (J. B. Walker, Tanganyika; unpublished). Lion (Lewis 1933, wileen 195013, Theiler, Walker, and wiley 1956). Cheetah (wileen 19502).

"Game" (Wilson 1950A). Bushpig (Santos Dias 1953B). Warthog

(Bequaert l930A,1931, Santos Dias 1953B).


Life History

Details of the life history under laborato conditions will be presented by Theiler, Walker, and Wiley (1956). Observations on the seasonal occurrence of various stages are presented below.


R. com situs (= R. ayeri) is included in the ecological zone referred to as the R. Ti endiculatus .. 2.. varie atum association (of. page 271.), but res ric ed o ghland ores s where it may occur locaJ_ly together with R. kochi (: R. jeanneli).

It is likely that comasitus and kochi were once more isolated than they present y are an that they now occupy in part


the same unique ecological zones due to movements of wild hosts or of domestic hosts. They are sympatric species in which hybridization is not known to occur.

The highland range of R. com situs is confirmed by the careful study of numerous records 5 Fgeiler, Walker, and Riley (1956).

Sudan specimens from a buffalo near Nimule, which is a savannah area at the level of the Nile River, 2,059 feet elevation, might appear to be exceptions to the highland concept of this species. They were, however, collected in December, shortly after the end of the rainy season, when there is a tremendous mvement of outlying animal populations towards the river. It seems probable that the buffalo from which these ticks were taken had recently come to the river from the nearby Acholi mountains, where he had acquired these parasites.

In Nyasaland, adults were collected only in December and January (middle rainy season), when adults of the closely related 17;. capgnsis were absent (Wilson 19508).

Matthysse (1954), working in Northern Rhodesia, considers it noteworthy that adults of com situs prreceed those of g. a diculatus, being found abundantly Before the rains, in Sept r ~r, and also being present in July, August, and November. Rains commence in November. This factor may be of importance in the transmission of East Coast fever during the absence of adult brown ticks. ‘Cattle examinations during the latter part of the dry season and during the early rains will show many brown ticks on the undersides of the body, in the tail brush, and on the

feet, but not in the ears. These ticks are largely 5. com situa(= R. eri) (Matthysse 1951.). The same author lists a single

colIec on from the ears of cattle.


CATTLE: A vector of East Coast fever (Theileria parva).


The confusion regarding the taxonomic position of this species is reviewed in detail by Theiler, Walker, and Wiley (1956) in a report so easily available to all specialists who might be concerned with this matter that it is not abstracted here.

These authors, with admirable conservatism, persist in refer...

ring to that tick herein called R. co situs by the name eri. However, their various rearing and ~onfl studies show

gyeri to include all morphological and ecological features of R‘.

ca nsis com situs and to be a valid species and taxonomic entity, separa e and gistinct from R. cagnsis, which they have also reared

through the F1 generation. They say: ‘As to whether eri is 11. com situs or not, we are inclined to think that it is, we are at %he moment not in a position to commit ourselves". In their smmnary, it is stated that: "(R. ayeri) is shown to be a valid species and is in all probability synonymous with Neumann's 1897

_R_. compgsitus" .

While there is some possibility that eventually R. co situs and R. geri will be shown to be separate species, this at present

appears so unlikely that I , more raahly than nw friends, am calling this material R. comasitus.

Santos Dias (194811) attributed a slightly misshapen specimen to R. ayeri.

The Sudan material has been checked by Dr. Theiler.


Males: Size edium to large (4.00 mm. to 7.75 mm. long). Scutal punctations are nuerous, very closely spaced, but mostly noncontiguous, uniformly large in central area (in R. capensis, large punctations are scattered among numerous smaller punc a_ions in central area), fewer or absent bordering at least the anterior half of the lateral grooves. The cervical area may have somewhat more variable punctations within lateral grooves (few in R. ca nsis). Cervical pits are short and deep; cervical grooves are s ow, diverging (frequently indistinct) (deep and long

capensis (which has punctat

in R. ca nsis). The body margin is regularly rounded or slight. ly'EulgIng posterior of the eyes*. Lateral grooves are deep, extending from usually clearly.marked pseudoscutum to margin between second and third festoon. The posteromedian groove is long and.narrow (possibly wider and sometimes shorter in R.

ca nsis); paramedian grooves are narrow. A small d0rS&I_hup o coxa I is visible. The basis capituli is nearly twice as wide as long; lateral angles are at the basal third and acute. The color is dark brown (usually light brown in R. ca nsis) to black. Adanal shields are of the widely triangular ype w th rounded junctures and margins and a slightly emarginate inner margin.

The wide, glossy scutal periphery and the numerous, regular scutal punctations are striking.

Females: This sex has a similarly wide, glossy border of the dark own or black scutu, with but few, small puctations outside the definite lateral grooves, which extend the full length of the scutum. The scutum is, therefore, quite distinctive. This feature, together with the rounded scutal margin (sometimes slightly indented posterior of the eye), nuerous, uniformly large punctations in the central field and a few small punctations anteriorly, and scutal length (only slightly wider than long)

rather easily separates R. com situs from the female of E. ions reaching the lateral scutal

margin, slightly greater scutal width, and nuerous small punc_ tations irregularly scattered among fewer large puctations). Cervical grooves are short and deep. Females are about 7.5 m. long and 5.0 mm. wide, scutum about 2.2 mm. long, ad 2.3 m. wide.

Note: In the Sudan tick fauna there should be little dif_

ficulty in determining E. com situs. The criteria separating this species frou1§. capgnsis have Eeen included above because of the


*According to Santos Dias (l949F) the body outline of R. capensis

bulges more than in 2. co situs (a Q. ayeri) just posterior o the eyes. This is not necessarily true in nonrobust specimens.

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