study of comparative morphology in the genus Rhipicephalus 

 and of chaetotaxy in the family Ixodidae led Pomerantzev ll936J 

 to reconstrxict radially generic concepts of this family. This 

 approach merits further investigation; however, the pitfalls of 

 hasty conclusions based on worn or poorly-preserved field col- 

 lected specimens, in which the chaetotaxic picture is imperfect, 

 may resTilt in additional confiision of species concepts (Hoog- 

 straal 1955C). 



Rhipicephalids tend to considerable variation in appearance 

 and morphological details oidjig to crowding on the host, welfare 

 of immature stages, and availability of suitable hosts, factors 

 that play a part in the determination of size, robustness, and 

 even certain physical characteristics. Distinguishing characters 

 in many specimens tend to become so generalized that diagnosis 

 is difficult. This is especially true for females. The question 

 of biological races remains to be explored; many data suggest 

 this phenomenon to be operable in certain groups of rhipicephalids. 

 The genus is divided into clearly defined species and species 

 variable enough to cause confusion. It contains extremely common 

 £is well as rare species. 



Host predilections within this genus are fairly wide among 

 several groups of available animals, althovigh the lack of interest 

 in other animals easily available in the same area is conspicuous 

 by rarity of records of their infestation. A few species, such 

 as R. pravus , have an exceedingly wide host range, being common- 

 ly Teiken on man and all domestic and many feral animals, such as 

 carnivores, antelopes, hares, birds, elephant shrews, elephants, 

 buffalos, and others. Other species, sxich as R. distinctus from 

 hyraxes, are known only from a single kind of "HosTT It is sig- 

 nificant that immatures and adults of most rhipicephalid species 

 do not attack birds and reptiles. 



The life cycle is either the two host or the three host 

 type and hosts of immature stages may be either the same as those 

 parasitized by adults or smaller and different animals. In some 

 species, records of lajrvae from both cattle and rodents are so 

 common as to confuse the picture of the preferred hosts of this 

 stage. R. appendiculatvis is an interesting example in point. 

 In R. s. ~simus there is so much data indicating immature stage 

 preSiiection for burrowing rodents that it is disconcerting to 

 find that in certain areas where this tick is common larvae are 



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