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for birds is most important for the survival and distribution of these species. Bird migrations may be of extreme importance in
spreading certain ticks; in Egypt a considerable body of yet un. studied data is being amassed on this subject.
The apparent adaptability of some halommas and rhipicephalids in altering the number and kinds of hosts they require when and if the situation demands is a most important factor where the supply of a variety of hosts is a critical factor of survival, which in turn determines distribution.
The only serious studies on African tick distribution are those of Theiler (l948,l949A,B,1950A,B,C,l956), Theiler and Robin. son (l953A), and Theiler and Salisbury (1956), for South Africa. In these, a combination of valuable criteria, i.e., vegetation plus range, mean, and seasonal distribution of temperature and rainfall, are carefully correlated with localities from which ticks have been collected. Vegetation types are shown to have a close kinship to outlines of tick distribution and the same appears to be largely true in the Sudan. These reports should be studied by anyone interested in the geographical distribution of ticks. Theiler frequently mentions uneven distribution, an aspect of the overall picture often most difficult to evaluate because of the complex factors mentioned in the present brief
For epidemiological and economic puposes tick species to be considered zoogeographically are more numerous than those thai may be readily considered academically strictly as indicators of zoogeographic Districts. Domestic animal parasitizing ticks, so important from the standpoint of human and animal diseases and numerically so common in observations and collections, are often more widely distributed than they might be in the absence of domestic hosts. Similarly, host specific ticks of wild animals, which are frequently those rapidly disappearing with the advance of civilization and hunters, are becoming more restricted in their contemporary range. In the following discussion an at. tempt has been made to strike a functional medium from both the practical and the academic standpoints.
The known Sudanese tick fauna comprises 62 identifiable spe_ cies plus two additional subspecies. It is conservatively esti_ mated that twelve to fifteen additional species remain to be dis. covered here and that when a future count is made the presently unknown components of the fauna will include approximately equal numbers of northern, eastern, and western species. Of the 64 known forms, ten are either Palaearctic in origin or are tents. tively referred to this Region, one is an introduced American (Neotropical) species, and 53 are Ethiopian.
H. dromedarii A. rsicus
The hyalomas are Palaearctic in origin and distribution al_ though they invade a narrow vegetated northern fringe of the Ethiopian Region. H. im eltatum has also gained fairly extensive foothold in the savann s o est Africa. The first three spe_ cies listed above conceivably could have reached the far flung areas where they do exist even without the assistance of domestic animals although there is little doubt that these vehicles have greatly facilitated their spread. Details of the distribution of H. detritum and H. mar inatum in the Sudan and elsewhere outside of the Palaearctic Hegion in Africa are vague.
I. vespertilionis and A. persicus probably should be treated as Palaearctic species that have been able to establish themselves as far south as the Cape through bat and human agencies.
Consideration of Q. savisn i, A. reflexus, and I. 5. sim lex as Palaearctic species is entirely tentative. The xerophi lC tampan ranges from India to Southwest Africa and its distribution has probably been influenced by common association with camels, except in southern Africa where other factors must be considered. 0. savivn*i in the Sudan is confined strictly to arid areas. The bat parasite I. s. sim lex is known only from a few, scattered Oriental, PaIaearctic,an Ethiopian records that defy zoogeograph. ical evaluation. The pigeon parasite A. reflexus, probably Palae
ctic in origin though possibly Oriental, is seldom established 5 tropical Africa; the single population of this species known ;om the Sudan may already have died out (page 75).
,- In surmnary, H. dromedarii H. excavatum H. i eltatum and ;. savi@i might be considered as nor@ 1' nhabitangs of the semi.
sser s or short grass savannahs of the Sudan, although extensiveJ distributed by domestic animals. The presence of H. detritum ‘ad £1. mar inatum in the Sudan is inexplicable on the-basis of
ur presenfi Ebrmation. The two bat parasites, I. s. sim lex
nd I. ves rtilionis are not unexpected due to their hos s light range. A. Ersicus and A. reflexus are here as a result
i‘ human'activities. - ___—'
Fifty-three of the Sudan's 64 tick species appear to have ariginated in the Ethiopian Faunal Region and few exist elsewhere except for the now cosmopolitan R. s. san ‘neus, A. -brum ti that reaches a comparatively few Tniles lil'1%O Egypt, E varie"atum that has become established adventitiously ‘in the West IE1 es.
i The Ethiopian tick fauna of the Sudan is largely East and ‘South African in origin. It appears best to dispose briefly of - the uncertain elements and of the small and relatively unimpor- tant West African and montane components of the fauna before
'- considering the bulk of the species.
Several species in the present collection are represented by so few specimens and data that inferences as to manner of occurrence in the Sudan or in certain local areas should be postponed pending further facts. A. reflexus, detritum, and . H. mar inatum have been discussed under Palaearctic species 5 -(page E p The single specimen of pompgsum appears to be far from ' its favored montane habitat and movements of cattle between
montane areas known to be infested and Yei are not believed recently to have occurred. This specimen may, however, point
to a limited, undiscovered focus in poorly..explored mountains ne: Yei. )
I_i_. lonfiicoxatus appears to be so patently a rare Somali lose. ‘N land tick t at t e single specimen from Bahr El Ghazal and others
reported from French West Africa are difficult to reconcile with previous information, and their significance cannot be evaluated properly until further specimens and data become available.
Mont ane Components
The Imatong Area mountain masses (page 8591) harbor outliers of the flora and fauna of both the West and oflthe East and South , African Subregions that occur almost nowhere else in the Sudan. H. £mata, be uaerti, and kochi are typical West African Subregion forms 0 in the Imato_—_ng and Didinga Mountains. The few specimens of Earmata from the plains level around Torit _ are assumed to have een acquired by their hosts in the vicinity 5 of the single stream reaching this area from the mountains.
The bat parasite I. 3. sim lex has already been discussed under Palaearctic species (page SIB). Two other species, I.
schillin si and alluaudi, occur on monkeys and on shrews, respectively, in the Imatong forests and reach here from eastern and southern Africa.
R. com situs, a species of eastern Africa that also extends into limi 1535 areas of western and southern Africa, is generally associated with highland or montane areas but attacks a wide variety of game animals not necessarily confined to these zonesThe several specimens from the Sudan have been found near mountains but not actually in them. This species is tentatively categorized as montane on the basis of its known distribution elsewhere.
West African Components
West African savannah species in the Sudan fauna are B.
annulatus*, 2. circ%uttatus, cuspidatus, 2. long1._1s-and
~ *B. azmulatus is an introduced American species that in the
Ethiopian Faunal Region is known chiefly from the West African , Subregion. }
:R. simus senegalensis; the last two forms have limited extensions
into East rica. West African forest species, in the Sudan known only from montane forests and lower streambanks of the Imatong and
‘ nearby mountain masses of the east bank of Equatoria Province, are
H. armata, g. be uaerti, and §. kochi. The Imatong Area also Far rs several specialized East B'rican forms not found elsewhere in the Sudan.
The occurrence of populations of any of the first five species
listed above outside of the Raga..Loka Area (Figure 328) is excep.. tional.
n It should be noted that the term West African, as here used zoogeographically, applies to elements originating in the first six of the Faunal Districts listed in Figure 1. Several species logically considered as West African from a generalized -point of view and in common name terminologyuare not considered Nest African in the more strictly defined zoogeographical sense of the term. For instance, H. im essum, although confined to West Africa in the generalized gesgraphical sense, is a savannah species of the East African (zoogeographical) Subregion. H. ho i appears to be OOIIJIIDII in the savannahs of both Subregions; EEXL though it is difficult to determine in which Subregion it should be considered typical the evidence strongly suggests East Africa.
._ It V ,
E. reidi sp. nov. is tentatively included here as a species of the West Kfrican Subregion since it has been found in only a restricted sector of the Raga_Loka Area (Figure 328). Further investigation may modify this concept but it is unlikely that a large amount of data will ever be amassed on this curious spa. cies. The unique biological characteristics and distributional picture of the two species in this genus, combined with their localization in remote areas, confuse an interpretation of their pattern of distribution.
East African Components
Species limited mostly to the area politifially considered as East Africa are of considerable value as zoogeographical indicators for the present study. The fact that several of these species, such as Ambl omma emma and Rhipicephalus chellus, are not known to reach the an, is of additional in eres .