CMTRAL RAINIANDS AREA 



In the Central Rainlands, ticks of big game animals are ex- 

 ceedingly restricted or entirely absent. Few species typical of 

 tropical East Africa that do range into this zone extend fxarther 

 north. Some populations of North African hyalommas penetrate 

 this area though whether they are merely transported or actually 

 reproduce here is uncertain. The presence of two Palaearctic 

 species is intriguing. H. marginatxxm may be established here 

 from nymphs introduced hy migrating birds but this explanation 

 cannot be applied to the single host tick H. detritum . The north- 

 em limit of this Area is probably the raosT critical and definite 

 of any boimdary in the Sudanese plains save those of the few 

 nontane masses that rise from these plains. H. impressum is 

 found only in this and parts of the adjacent Srea to the north. 



The Nuba Mountains should be considered as a separate sector 

 of this Area but data on tick distribution are not yet sufficient-, 

 ly definitive to allow designation of these mountains as a dis- 

 tinct faxinal Area. 



FASHEE-BUTANA AREA. 



Here the desert aspect emerges. Further research will prob- 

 ably show that this Area may be divided into a southern sector 

 in which rare, small populations of several tropical African tick 

 species siorvive and a northern sector inhabited only by xerophilic 

 species. The narrow Nile Valley carries a small number of spe- 

 cies northwards to its great bend, beyond which only H. 1. leachii 

 is established. Various hyalommas, R. s. sanguineus , an3 0. 

 savignyi are tne indicator species oT t"His Area in which few 

 others are known to be established. Palaearctic components 

 are here a strong feature, especially in the north. Like the 

 Nuba Mountains in the Central Rainlands, the Marra Mountains may 

 prove to be a distinct f aunal Area after sufficient data have 

 been obtained from this region. 



ARID DISTRICTS 



BAIYUDA AREA 



No tick records are available from these harsh deserts al- 

 though rare populations of argasids and hyalommas are suspected 

 to occur in restricted localities. 



- 860 _ 



