they are beside irrigated, cultivated fields or in dykes. We have 

 never foxmd these ticks in burrows in the desert, even on the 

 Mediterranean littoral where burrows are frequently patently damp. 

 Foxes that pick up newly-molted adult ticks, probably from vegeta- 

 tion near grassrat biu-rows when they forage in cultivated areas 

 at night, retreat to very dry desert caves and dens to rest by 

 day. In these situations, evaporation from the host skin may be 

 the factor that allows the parasite's survival. 



A comparative study of the survival of Northeast African and 

 South African populations itnder local conditions of humidity and 

 temperat\ire should be of considerable interest. 



Theiler and Robinson (195 3A) have also found that H. 1. leachii 

 does not occxir in those parts of South Africa with over"~sixty days 

 of heavy frost per annum. It is generally absent from the arid 

 Karroo except where grasses are present. Altitvide does not effect 

 the distribution of the yellow dog- tick within the limits of crit- 

 ical frost days noted above. Variability of incidence in various 

 zones of South Africa is also discussed. 



According to Lewis (1939A), H. leachii (probably including 

 both subspecies - HH) occurs in all districts and altitudes of 

 Kenya but seems to prefer the shelter of dense shrub and grassy 

 woodlands. In some areas it is more common on dogs than is R. s. 

 sanguineus . "" 



Theiler and Robinson (loc . clt.) state that the immature stages 

 of H. 1. leachii may feed on dogs. Our experience in East Africa, 

 Egypt, "and Arabia indicates that nymphs are very rarely foimd on 

 roaming wild carnivores such as mongooses, civets, and jackals, 

 but that larvae and nymphs frequent rodent burrows. Onderstepoort 

 records (Theiler, correspondence) show one hundred collections of 

 nymphs from raurid rodents, one from cattle, one from shrews, one 

 from Felidae, one from hares, eight from elephant shrews, three 

 from fflustelids, five from springhaas, four from squirrels, three 

 from mongooses, and one from civet. It is obvious that many factors 

 governing the life cycle and possible variability in host preference 

 of immature stages remain to be determined from field studies. 



Roberts (1935) found larvae and nymphs in the Nairobi area 

 common on various field rodents and in their nests. These are 



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