152 



A recent note on the occurrence of 0. mouhata in the Middle Congo 

 [see this Review, Ser. B, vii, p. 51] draws from the author some observa- 

 tions regarding the distribution of this tick in tropical Africa. This 

 was first established by a map drawn up by Dutton and Todd in 1905, 

 when the presence of 0. mouhata in the middle Belgian Congo and the 

 region of the Cataracts was recorded. In most of the settlements 

 made by the Arab slave-traders, 0. mouhata soon appeared. When, 

 in 1890, the Arabs from the east were definitely stopped in their 

 march westwards, they had reached the post of Basoko on the Congo, 

 and had established many settlements around Stanleyville, but 

 although these settlements still exist and maintain trade relations 

 with many Arab centres of the south that are heavily infested with 

 ticks, Stanleyville has as yet escaped infestation. Previous writers 

 have recorded that ticks are more frequently found in Arab houses 

 than in native huts. This has been explained by the fact that the 

 former are drier, in better condition, and occupied for longer periods 

 than the latter ; for it is well-known with what frequency and facility 

 the natives break up and remove their settlements. The author 

 considers that another important factor opposes the rapid propagation 

 of this tick in the lower equatorial regions, namely, the great atmos- 

 pheric humidity that exists there at all seasons ; such humidity, 

 if it is not a direct obstacle to the multiplication of this parasite, at 

 least prevents it from surviving when deprived of man, its normal 

 host. When travelling in the south of Katanga, the author observed 

 that below 9° S., 0, mouhata seems to occur in every native dwelling, 

 however rudimentary. The country slopes gradually lower towards 

 the north-west and becomes decidedly more humid; as is shown 

 by the existence there of the great equatorial forest. 0. mouhata 

 does not occur there. On the other hand, the tick is uniformly present 

 in the region of the Cataracts, in Portuguese Angola, the Belgian 

 Kwango and certain parts of the French Congo. All these regions 

 where the tick is disseminated among the native population consist of 

 wooded or park land, where the dry seasons are sharply defined, and 

 although the inhabitants are constantly shifting and changing their 

 dwellings, 0. mouhata flourishes there. It seems logical to conclude 

 that in very humid regions, particularly those covered by the dense 

 equatorial forest, these ticks, temporarily deprived of their normal 

 host, rapidly succumb. It is obviously not because they lack animals 

 that would serve as occasional hosts ; elephants, warthogs, and many 

 almost hairless mammals exist in the forest, and antelopes are 

 frequently abundant. 



There is, in the north-east of the Belgian Congo, a stretch of country 

 that is threatened with the invasion of 0. mouhata ; this comprises the 

 mining regions of Upper Ituri and Upper Welle. Communications 

 have been maintained for several years between these regions and 

 Uganda along a caravan route. This route for a long distance runs 

 through open or slightly wooded country, and then for several days' 

 march crosses a vast expanse of equatorial forest. It will be interesting 

 to observe whether the forest belt will arrest its progress, or whether 

 it will spread over the northern plains without becoming established 

 within the forest itself. The author is convinced that the latter 

 eventuality will occur. 



