that the messy area in which adults usually feed influences to some extent the numbers of red ticks represented in collections made by Europeans though this is seldom a deterrent to "unspoiled" African assistants. An exception to the above statements, however, was made by Meeser (1952), who noted that red ticks on the impala antelope of southeastern Transvaal is infested on the genitalia and shanks and almost nowhere else on the body. R. e. evertsi, together with B. decoloratus, are the chief tick parasites of this common antelope there. Theiler's (1950B) study of the distribution of the red tick in South Africa shows that it is present in all types of forest, in all parklands except dry ones, and in all types of grasslands. It maintains itself with difficulty in shortgrass country and is generally absent from desert-shrub areas, but may persist in thorn country and in mixed desert shrub grassland. Altitude and low desert-shrub temperature do not limit the red tick, but rainfall below ten or fifteen inches per annum seems to be a limiting factor. There appears to be no seasonal variation in the activities of this spe cies. In parts of Africa warmer than South Africa, a somewhat higher critical level of annual rainfall is probably necessary for the red tick to maintain itself, but definite limits have not yet been as certained. As already noted, another subspecies (mimeticus) takes over from this subspecies in the arid areas of southwestern Africa but both are found together in the savannahs of western equatorial Africa. Such evolution of a rhipicephalid species in Africa is as unusual as the red tick's morphology and as its life cycle. In Kenya, the red tick appears to be somewhat more adaptable than in South and West Africa. There it occurs in the deserts of Northern Province, in coastal areas and open plains, as well as in forests above 8000 feet altitude; "in fact almost anywhere" (Wiley 1953). Wilson (1953) noted that the red tick occurs in both the same areas as the R. pravus A. gemma association (cf. page 681) and the R. appendiculatus A. variegatum association (cf. page 274). While absent from wet zones of Nyasaland and Tanganyika, it is the dominant species in the Masai grasslands and occurs seasonally in small numbers in dry areas of the R. pravus A. gemma associa tion. The ecology of this tick requires further detailed investiga tion. Around Mbui, Adamawa Province, Nigeria, the red tick forms sixty percent of the specimens in tick collections (Unsworth 1949). Reasons for this density should be interesting to investigate. In the Sudan, the red tick is absent in true desert areas but does occur and is common in a wide variety of forested savan nah and semidesert areas. In Moreau's (1933) study of ticks in the stomachs of the tickbird, Buphagus erythrorhynchus (Stanley) in Tanganyika, specimens of R. e. evertsi were found in three of 58 birds examined. They numbered one, six, and eighteen ticks per stomach. In Kenya, van Someren (1951) found three adult red ticks in the stomachs of two of the same kind of bird, but none were found in ten other of the same kind that he examined and none were found in stomachs of seven B. a. africanus. A further discussion of this subject is presented under A. variegatum, page 275. The concealed places in which the red tick usually feeds probably protects it from this predator except in special circumstances. Nymphal R. evertsi removed from hares, Lepus zuluensis, have been found infected with the chalcid parasite Hunterellus hookeri Howard, 1908 (Cooley 1934, see also note by Bedford in Cooley 1929). REMARKS Integumentary sense organs, which are fixed in number and location, and which are essentially similar in all stages of the tick, though more primitive in larvae, have been described and illustrated by Dinnik and Zumpt (1949). This subject has also been discussed by K. W. Neumann (1942). Preliminary studies on spermatogenesis by Warren (1931), which do not appear to have been completed, indicate that in R. e. evertsi a single spermatid gives rise to several sperma_ Tozoa of extremely variable size. Warren's observations differ considerably from those of Nordenskiöld (1920) on Ixodes ricinus. Misformed specimens of R. e. evertsi have been reported on by Santos Dias (1947B,1948A,1954H7. An egg toxin has been found in this species (De Meillon 1942). Symbiotes have been reported and discussed by several workers: Cowdry (1923,19250,1927), Buchner (1926), and Jaschke (1932). The arch of the eye has been briefly mentioned by Gossel (1935). Dönitz (1905) observed copulation by insertion of the male hypostome into the female genital aperture while the legs are used as clasping organs adjacent to the corresponding legs of the female but was unable to ascertain how seminal fluid was passed; Christophers (1906) stated that ob viously it is accomplished by transfer of spermatophores during the mating act. The life cycle and morphology of the red tick are so peculiar within this genus that a special subgeneric niche might seem in dicated for R. evertsi. Theiler informs me (correspondence) that Dr. Cooley also entertained this idea while he was in South Africa, but that the immature stages are so normally rhipicephalid as to dampen any urge to take this step 7. DISEASE RELATIONS MAN: Boutonneuse fever (Rickettsia conorii). CATTLE: East Coast fever (Theileria parva). Pseudo-east coast fever (T. mutans). Redwater (Babesia bigemina). Spirochetosis (Borrelia theileri). Not a vector of heartwater (Rickett sia ruminantium). A secondary bacterial infection by Corynebacterium pyogenes causes an otitis leading to the sloughing of the host's external ear when infested by larvae and nymphs. The virus of "a specific transmissible petechial fever of cattle" may be trans mitted to sheep by the red tick. SHEEP: Lamb paralysis (?toxin). Apparently not a vector of Nairobi sheep disease (virus). See paragraph above. HORSES, MULES, and DONKEYS: Equine piroplasmosis (biliary fevers) (Babesia equi and B. caballi). Spirochetosis (Borrelia theileri). IDENTIFICATION Males: The red tick is usually large (5 mm. long) though smaller specimens do occur. Its dark scutum contrasts greatly with the reddish body integument and saffron legs. The dark eyes are hemispherical, protruding, and orbited, similar to those of hyalommids but to no other rhipicephalids except R. oculatus (and, partially, to R. pravus). Scutal punctations are of medium and large size and so numerous as to cause the scutum to appear shagreened. Lateral grooves, a posteromedian groove, and para median grooves are pronounced. A large, painted process from coxa I is visible dorsally. The huge adanal shields, very wide and posteriorly semicircular in outline, are also unique. Female: This sex is colored as in the male and has similar scutal punctations and eyes so that it can never be mistaken. The scutum lacks lateral grooves. The larva and nymph have been described and illustrated by Theiler (1943B). Note: The subspecies R. evertsi mimeticus Dönitz, 1910(B), has yellow-ringed legs while those of the typical evertsi are unicolorous. |