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(Figues 208 to 211)

The exact status of this form is uncertain. Since first mentioned from French Somaliland (Hoogstraal l953D), a small amount of additional material, all from camels in the Somali biotope, from British Somaliland and Gebel Elba of southeastern Egypt, has been seen. An attempt will be made to obtain living material for rearing studies in order to define the morphological characters and taxonomic position of this form, both sexes of which resemble extreme variations among other species. The con. sistency with which males and females of this form are found to. gether throughout coastal eastern Africa north of the equator arouses suspicion that this is a distinct genetic entity.

The male subanal shields lie directly posterior of the central axis of the adanal shields; the scutum has characters in common both with heavily punctate H. mar inatum and H. impeltatu. The female scutum is also similar to thaé of Both of_these species but the genital apron is like that of H. dromedarii although more depressed posteriorly. The outline of_this apon in the specimen illustrated (Figure 211) represents the maximum width of this structure observed among available material; in other specimens it is more narrowly and elongately triangular, as in H. droma_ darii. The apron is not flanked by two lobes as in H: impeltatum, and its profile differs greatly from that of H. impeltatum.


Ixodes ticks are highly specialized in their habits. They frequently parasitize small or seldom-examined hosts and are so small themselves that they are easily overlooked. Of some twentyi five species in Africa, six occur in the Sudan. Only sixteen specimens of the whole genus have been collected in the Sudan, all but three of these by the writer. This paucity or material is in striking contrast to Kenya, Cameroons, and Nigeria, where careful collecting is fairly productive for several species.

Phylogenetically, Ixodes ticks occupy a solitary position as a unique, highly specialized branch from proixodoidea stock. Sev. eral exceptional morphological characters may be seen easily by comparison of Ixodes illustrations with those of other genera. The absence of eyes in this genus is believed by some to be a primitive character and the sexual dimorphism of the mouthparts is unparalleled in other ixodid ticks.


Intraspecific variation in the African Ixodes fauna is still poorly understood because only small amounts of material from many localities are available and probably also because these variations do not conform to those typically expected in ticks. Dr. D. R. Arthur of King's College, University of London, is pesently under. taking an exhaustive study of this subject.

Biologically, ticks of this genus offer a wide field for research; their habits differ from all others. To elucidate this, Nuttall (l9l1A) erected the following biological criteria for Ixodes ticks:


I. Species in which both male and female occur on the host.

(a) Species in which the sexes are found in copula
on the host (usually on wandering hosts).

(b) Species in which the sexes are found near each

other on the host (on either wandering or fixed
habitat hosts).

II. Species in which only females are found on the hosts,
and in which males may or may not be known.

Although the males of species confined to the Ethiopian Faunal Region (exce Ixodes nairobiensis Nuttall, l9l6 and Z. hoogstraali Arthur, 1955 are Eown, their Ehits are still obscure.

The genus Ixodes has been reviewed by Nuttall and Harblmton (1911), to which important additions have been made by Nuttall (l9l3C,19l6). The African representatives of this genus are reviewed by Arthur (ms.), who also proposes a number of new species.

Careful examination of rodents and other small animals, and of dogs and other domestic animals will probably reveal other spa. cies in the Suian, especially on the west bank of Equatoria Prov. inoe. Search in rodent nests, animal lairs, and bat caves and retreats should prove fruitful.

No African Ixodes has been reported to transmit hmnan diseases, but at least Ixodes cavi al and I. rasus are known to bite man.

In southern A1'17:|I:-a_, . ru icundus is an 1' mportant cause of tick paralysis of sheep. -I. Dll'OSU.S, to which this condition is most commonly attributed ih iJ.'\.(-‘:1‘&.El.1I‘8, plays no known r31e in this affliction; early misidentification was the cause of this fre. quently quoted misstatement (Theiler, correspondence).



l. Legslo erthan body. (From bat

Figures 252 E 2:” Legs not longer than body. (Not batS).Q.UIII.——...-.........._.._..........._...._.‘--..2


"The males of 2. nairobiensis and of E. _s_. simplex are not known.

Palpal base forming a lateral pro.

jection from basis capituli, palpi

converging anteriorly. Scutum

sharply narrowed posteriorly.

(Shrew parasite, uncommnly on

other insectivores and rodents)...................I. ALLUAUDI

Figures 339"E'xH1ZU

Palpi normal, arising from anterior

of basis capitu].i and parallel.

Scutum gradually or bluntly rounded posteriorly.................................................3

mfl ~QQ..QQ..’...QQ.QQQQQIIQQQQQZU ~I Figures'@'and 223

Anal grooves not lmited posteriorly.........................l.

Scutum with faint, shallow puncta.

ti°nsI.I.Q.’..Q‘.QQ.Q......Q.'.Q.......QQ.......2I Figures ZIFETD

Scutum with numerous large, uneveh

ptmctations. (Monkey parasite)................_I_. EHILLINGSI
Figures '22'5"E_2'2'7
Legs 10 er than body. (Bat



Palpi arising laterally from basis

capituli . Scutum abruptly conver.

ging posteriorly , with few medium

ptmctations ; cervical grooves lateral grooves fine.....................I. ALLUAUDI ’ "Figure BZI

Palpi normal, arising from anterior capitu-L1000OQOOOIOOOOOOOOOOOOOOOOOIOOOOQOOOO3


Anal grooves horseshoe shaped or elliptical, not united posterior1y..........................l.

Anal grooves either united poste-
riorly or parallel or divergent


Scutum at least 1.5 times as long
as wide; punctations few and fine;


Scutum only slightly longer than

wide; punctations large, distinct,

deep; lateral. ridges absent. . . . . . . . . . . . . . . . . . . .I. HJHIILDIGSI Figures ’Z2'8"EH"229

Anal groove closed posteriorly. . . . . . . . . . . . . . . RASUS SUBSP.
Figures_2'2Z-and 225

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