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BIOLKXEY

After having collected numrous specimens of Ixodes rasus from may small mammals in Kenya, from sea level tT8UU5 feet elevation, it was surprising to find this species so rare in the Sudan. From Pearse's (1929) report on Nigerian ectoparasites, I. rasus appears to be connnon on small mammals there. The reasons for these considerable differences in local populations remain to be explained.

Nuttall (1911) categorized I. rasus in the biological group within the genus Ixodes in which-malesi and females are usually found together on a host that either wanders or does not travel far and in the subgroup in which the sexes are often found in co¥a on the host. Present evidence partially supports the

nc usion of Ixodes rasus in the last subgroup and careful col... lecting may suhsequently prove that this species should be so considered.

Systematic search probably will show Ixodes rasus to be a connnon tick in many parts of tropical Africa. Eaten-:.’a.'rTa'.tion of rodents in certain areas should prove fruitful. Seeking for every tick on a variety of anirmils will undoubtedly reveal a few, small inconspicuous, well_hidden Ixodes ticks along with more apparent, more numerous , larger, EH more colorful ticks of other genera.

Questions concerning the biology of Ixodes rasus in its various forms (i.e. subspecies) offer a c~ in one of the most fascinating zoological areas of the world.

DISEASE RELATIONS

Unstudied .

REMARKS

Schulze (1941) noted certain features of the haller's organ of 2. rasus (cf. also K. H. Neumann 1943). A comparison of this

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organ with that of other Ixodes species is presented in table form by Arthur (19563).

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Remarks on morphology of this species are contained in papers by K. H. Neumann. These have not yet been seen and complete ref. erences are not available except for: (191.2) Z. Morph. bkol. Tiers, 38(2):358 362. (Mor ology of subcoxa of subspecies cumulatim. unctatus ; and (191.5 Zool. Jb. (Anat.), 69(2):286, fIg. 3. Jakob

included this species in his review?’ of the relationship of tick genera from the standpoint of comparative morphology.

Both sexes are readily distinguished by their completely closed, usually circular anal grooves, an easily observed character in all specimens except some greatly engorged females in which the anal area is depressed and the associated grooves are difficult to dis. cern. Only one other African species, Ixodes andanus Neumann, 1906 (with which Ixodes laceus Uarburton, , rom Uganda is quite possibly synonymous , s own to have closed anal grooves; these are not circular but characteristically oval and unite in a slight posterior elongation. Eandanus has not yet been found in the Sudan.

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Schulze (l9l.3A) indicated that circular anal grooves are char. acteristic of this species but that some specimens in which these grooves are expanded to a broad oval outline are merely atypical individuals of the same species. According to Schulze, the anal grooves of _I_. rasus may even be narrowed posteriorly.

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Schulze (191.35) differentiated three subspecies of I. rasus and one "related species" as follows:

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I. rasus rasus: Short, broad palpi and hypostome; retro. grade aur c as (lateral spurs of ventral basis capituli); pro. nounced single ptmctations on scutum. (From Cameroons).

I. rasus cumulatim tatus: Long, narrow palpi and hypo. stome-; perpendIcuIar aurIc%Iae; and small scutal punctations, some of which appear to be formed of a small group of smaller, contiguous punctations. (Tanganyika to Fernando Po)

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I. rasus eidmanni: The same characters as given above for I. rasus rasus, Kt “more strongly chitinized and darker", and

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denticles of hypostome with a small apical "hookF, proximity of sensory organs in the integument, and absence of a definite "peripheral zone" of the integument. (Rio Muni, or Spanish Guinea) .

I. vanidicus: Similar to I. rasus but with anal grooves horseshoe shgped or circular but not closed posteriorly. (Tanga. nyika to Cameroons).

IDENTIFICATIN

Males are characterized by circular anal grooves (see REMARKS above), narrow marginal fold beside the scutum, fairly many to numerous fine scutal puctations, and short palpi with segments 2 and 3 of about equal length. This reddish brown species is about 2.8 mm. long and 1.8 mm. wide and has a broadly rounded posterior margin. The tarsi are usually humped but in some specimens which otherwise conform to this description they are tapering.

Females also have closed anal grooves. Their scutal puncta. tions are similar to those of males. The hypostome and palpi are long and narrow and the basis capituli ventrally has a large spur (auricula) arising from each lateral margin. The tarsi are either tapering or somewhat humped.

Note: As presently considered, any African Ixodes male or female with circular, closed anal grooves is I. rasus. Within the large amount of material seen in various EolIections there is

considerable variation in most other characters, the significance of which await to be determined by Dr. Arthur.

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L N 9 0"‘ EIJUATCIRIA PROVINCE REDCRD l Lotti Forest Colobus pglykomos dodiggae Apr

Lotti Forest is at 4500 feet elevation. This is the only record of this species from the Sudan. About a dozen monkeys of the same species examined in Lotti Forest and at other places at different altitudes in the same forest were free of ticks. An equal number of monkeys, Cercopithecus mitis stuhlmanni, from Lotti Forest were tickless, as were numerous specimen's of other monkeys (Setzer 1956) examined elsewhere in the Sudan.

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DISTRIBUTION

I. schillin si, a parasite of East African Colobus monkeys, does hot appear %3 range outside of wooded savannah and forested areas. It is the sole described African representative of a complex of species occurring in Asia, Madagascar, Australia, and Europe.

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KENYA (Nuttall 1916. Lumsden 1955. Arthur, ms. See Hosrs below). TANGANYIKA (Neumann l90l,l90'2C,l9l0B,l9ll. Nuttall and Warburton 1911. Morstatt 1913. Arthur, ms.). ZANZIBAR (Arthur, ms. .

sourrman AFRICA: MOZAMBIQUE (Neumann l9l9A,l9ll. Nuttall and Har5u_1:ton I9II. Santos Dias 1953B).

HOSTS

Man is parasitized by H. s. schillin si according to a single record for a female tick of thIs species Iron Njoro, Kenya (Lumsden

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