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Integumentary sense organs, which are fixed in number and location and essentially similar in all stages, though more primitive in larvae, have been described and illustrated by Dinnik and Zumpt (1949). These are the organs that Delpy (1938) had previously referred to as spiracles ("stigmates respiratoires").

Pervomaisky (1949) was unable to rear a full Fı generation from parthenogenetic females of H. dromedarii. Abnormal specimens have been described by Pavlovsky (1940) and Alfeev (1948).

The feeding of large numbers of this tick (= H. asiaticum induces inflammation of the host skin that hinders normal engorge ment, especially of females that are likely to die as a result. When additional species compete for space, "a further antagonistic factor increases the obstacles" (Pavlovsky, Pervomaisky, and Chagin 1954).

Warburton and Nuttall (1909, page 71) produced an excellent illustration of H. dromedarii (H. aegyptium) but the legend, inferring South Africa as the source, is misleading. Apparently the only specimen from South Africa is the abnormal one (figure 18), the identity of which is uncertain.

"H. asiaticum", which Delpy considers to be a synonym of H. dromedarii, is still treated by Soviet workers (Pomerantzev 1950) as a separate species with several subspecies and with a wider geographical range than H. dromedarii. This form is less robust, smaller, and more slender, with a shorter posteromedian groove than in giant males typical of H. dromedarii. The fe males are more elongate than the typically robust female H. dromedarii and the length width ratio of their palpi and of their scutum is longer. Such individuals are also encountered in African populations. Delpy (1946) first considered the short, wide palpal shape to be diagnostic but further studies indicated so much variation that "applied strictly to determination of isolated specimens, (this character) would have led to errors. (Also) the ratios that are true for a young, recently molted tick are no longer accurate when this tick has aged and become engorged". The shortness of the posteromedian groove appears concomitant with the general lack of robustness in these smaller and more slender ticks.

Feldman_Muhsam (1954) states "The type specimens of H. drome darii asiaticum as well as H. asiaticum citripes differ from H. dromedarii and are not synonyms of H. dromedaril". Without further explanation, it is impossible to evaluate this remark.

DISEASE RELATIONS

MAN:

A host and vector of Q fever (Coxiella burnetii).

Experimentally, this tick can be infected with the virus of Russian spring summer encephalitis, with the virus of mosquito borne autum encephalitis from the Russian Maritime Province,

with the virus of a Japanese mosquito-borne encephalitis.

CATTLE: Theileriasis (Theileria spp.). This tick (as H. asiaticum) is apparently not a carrier of brucellosis (Brucella spp.).

CAMELS:

Theileriasis (Theileria camelensis).

DENTIFICATION

Males: Typical males are recognized by (1) large size (average length: 5.7 mm., range 5.2 mm. to 7.0 mm.; average width: 3.8 mm., range 3.0 mm. to 5.0 mm.), (2) distinct lateral displacement of the subanal shields, (3) short, deep lateral grooves limited to the posterior third of the scutum; and (4) few, large shallow punctations variously scattered over the surface and complete or almost complete absence of other puncta tions. Also distinctive is the deep, usually narrow, postero median groove extending from the distinct parma to the scutal midlength. This groove is bounded on either side by converging ridges; laterad of these ridges are deep, wide, often rugose paramedian grooves. The paramedian grooves are of variable length, and posteriorly delineate the two median pairs of fes. toons, which are often massive and which are larger than the more or less distinct three lateral pairs of festoons. Another pair of parallel ridges may be present between the paramedian grooves and the lateral grooves.

Variations of the above characters are as follows: Small punctations may be present and rarely may be obtrusive enough to suggest H. impeltatum; also a line of large punctations ex tending anteriorly from the apex of the lateral grooves may sug. gest H. impeltatum. In engorged specimens, at least, differences in the posterior area of the scutum separate such specimens. In some specimens a dense field of small punctations may be present posteriorly, suggestive of H. excavatum. The subanal shields are sometimes divided into two pairs, but very few such specimens have been seen during the present study. In unengorged males, the subanal shields are closer to the central exis of the anal shields than otherwise, but their center is still exterior of the central axis of the adanals. Color varies from yellowish brown through dark brown to brownish black. The legs are usually paler than the scutum and the segments may be ringed by a paler band.

Females: Typical females may be recognized by (1) the nar. rowly elongate and triangular genital aperture, which in profile slopes gradually, (2) the comparatively wide scutal outline (length width ratio about equal, (3) few, large, scattered punctations and frequent rugosity of the scutal surface, and (4) large size. The palpi are usually twice as long as their com bined width. The color varies from yellowish brown to black; the legs are usually paler than the body and may be concolorous or ringed.

The genital aperture is most distinctive and hardly variable. In newly molted females its outline is slightly concave sub apically, but in engorged specimens the lateral margins are usually straight. The narrowly triangular outline is apparent ly never lost. A narrow, raised integumental fold surrounds the apron,

The scutal outline is widest just anterior of the eyes. The wide, deep, long cervical grooves are usually rugose as is also the scutal surface of most engorged specimens. From ten to twenty (average thirteen) large punctations are scattered over the central field and an equal number occur in each scapular field. Average newly molted specimens measure about 5.5 mm. long by 3.2 mm. wide, but engorged individuals may be 30.0 mm. long and 15.0 mm. wide. Scutal length is about 3.2 mm., width about 2.8 mm.

The larva and nymph (as H. asiaticum) have been described and compared with those of other species by Bernadskaia (1939) and (as H. dromedarii) by Feldman_Muhsam (1948).

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Figures 166 to 167, 0, dorsal and ventral views
Figures 168 to 169, 7, dorsal and ventral views

A, & genital area. B to D, & genital area outline and profile.

B, unengorged. C, partly engorged. D, fully engorged.

HYALOMMA EXCAVATUM
Egyptian Specimens

PLATE XIL

435

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