HOSTS All domestic animals are attacked by adults of this tick. Available data does not indicate that among these animals H. impeltatum shows any marked host predilection. In Egypt a number of specimens have been taken feeding on personnel during field trips. Wild animals known to be infested are gazelles in Egypt man. Hosts of immature stages are rodents, hares, birds, and At Amara, on the Tigris River in Iraq, Lt. R. A. Buxton reared adults from nymphs taken from hares and from a redstart, P. phoenicurus (= Ruticilla pluvenicurus) (Nuttall lots 3239 and 3240 in BMNH). In Egypt we have reared many adults from nymphs that have dropped from both the lesser and the greater Egyptian gerbils, Gerbillus g. gerbillus and G. p. pyramidum, and fewer from the following animals: lesser Egyptian jerboa, Jaculus j. jaculus; fat sandrat, Psammomys o. obesus; Egyptian hare, Lepus capensis aegypticus; and man. Although Rousselot (1948) reared this species, he furnished no data on the hosts of the immature stages either in the labo ratory or in the field. BIOLOGY Life Cycle Rousselot (1948) claimed that H. impeltatum (= H. brumpti) is a three-host species that in his French West Africa laboratory completed its life cycle in about three months. Results of studies in NAMRU-3 (Cairo) laboratories will be presented when completed. Ecology Although H. impeltatum is a tick of arid and semiarid regions, small populations also exist in certain African savannah areas. Biological and ecological characteristics and limitations of this species are still poorly known. As noted above, immature stages are found in common association with desert and desert edge rodents in Egypt. In Nigeria, where H. impeltatum is almost entirely confined to the more arid northern provinces, it is sometimes the most common tick collected on cattle and appears to require a drier climate than do H. truncatum (= H. transiens), H. impressum, and H. ru fipes (Unsworth 1952). Adults are found around the anus and udders and in the axillary regions of their hosts. DISEASE RELATIONS Apparently this tick is not a vector of Theileria annulata of cattle. Note, from Egyptian records, that nymphs and adults are known to feed on man in nature. REMARKS The comparative size of each stage and sex has been noted by Campana Rouget (1954). The remarks below are based in part on specimens originally identified (as H. brumpti) by Dr. L. P. Delpy, on his remarks (correspondence) on this material, and on our further observa tions of additional collections consisting of some 2000 spec_ imens. IDENTIFICATION Males. In TYPICAL specimens, (1) the exterior position of the comparatively large subanal shields, (2) the lateral grooves that extend anteriorly at least to the scutal midlength, and (3) the numerous, moderate size (few large), shallow, scutal puncta tions that are uniformly and widely distributed over most of the scutal surface, is a combination of characters easily separating males from those of all other species. Variation in each of these characters are as follows: (1) In specimens that have fed, the subanal shields are always situated well exterior of the axis of the adanal shields; they are usually borne on a slightly rounded, elevated protrusion of the ventral integument, and usually extend posterior beyond the body margin. However, in unfed specimens, where the sub anal shields are still closely appressed to the ventral integu ment, these shields may appear to be in line with the central axis of the adanal shields. Close observation reveals that the base of the subanal shields is in an exterior position but that the unique tilting of the subanal shields in a medially-directed position gives the first impression that they are situated direct ly posterior of the adanal shields. In fed males, the subanal shields are usually vertical and parallel. (2) The lateral grooves are usually well delineated and extend from the festoons in a progressively more shallow line almost to the eyes. In some specimens, they are more or less obscured, at the level of the scutal midlength and anteriorly, by scutal punctations; questionable specimens should be tilted towards the source of the light. In other individuals, the anterior extension of the lateral grooves con sists chiefly of a distinct row of more or less contiguous puncta tions; such specimens may be confused with H. dromedarii, and, if the subanal shields are still closely appressed to the ventral integument, possibly even with H. excavatum. (3) Punctations are usually very slightly larger, deeper, and more dense posteriorly than elsewhere on the scutum. Punctations over the scutum are typically dense but not contiguous, regular, medium size with a few scattered larger, deeper ones among them, and fairly shallow. The number and placement of these punctations is subject to con siderable variation; in some specimens the central scutal area may be almost devoid of obvious punctations; this is especially true in engorged individuals. Other characters are as follows: The area just anterior of the festoons is almost always slightly depressed and contains a long, narrow posteromedian groove, and a pair of shorter, wider, and deeper paramedian grooves. A parma, the color of which may be lighter or darker than the rest of the scutum, may be present, or may appear as a normal median festoon. Two definite pairs of festoons and two more or less fused pairs lie on either side of the parma or median festoon. Delpy states that the scutum is flat, actually it is usually more or less arched, especially in males that have fed. The scutal color varies from dark brown to black; excep tional specimens, usually very small ones, may be lighter. The leg segments are usually pale anteriorly and posteriorly and darker centrally, but they may be entirely pale yellowish. Female: The scutum posteriorly and centrally has numerous rather regularly spaced, moderate size, noncontiguous punctations. Scattered among them are several larger and deeper punctations in two parallel rows centrally. The moderate size punctations are usually mostly discrete, but exceptions to this are common. Anteriorly and in the scapular areas, punctations are large and deep; in the lateral fields punctations are absent or present. The deeply depressed cervical grooves are more or less rugose, and the punctations in them are more or less contiguous. The scutum of engorged specimens frequently has less distinct punc_ tations and grooves. The scutum is generally dark brown in color. It is definitely longer than wide, but the ratio may be reduced in some newly molted, misshapen, or greatly engorged specimens. The genital area is distinctive. The central genital apron is an elongate triangle much like that of H. dromedarii but shorter, wider, and usually not quite so narrowly pointed apically. In profile, it definitely bulges anteriorly and is depressed posteriorly. An important principal additional feature is that, in unmated specimens and in mated but not greatly engorged specimens, this genital apron is bordered on each side by a slight bulge that gives the genital area a trilobed appearance not found in any of the other species with which H. impeltatum may be con fused. This characteristic is maintained with only slightly less distinctness in greatly engorged females. Female body size, in all except runts, is always large. The legs are like those of the male. NOTE: Very small, rounded, globose, pale runts appear com monly with typical specimens. Their diagnostic characters are frequently modified. In field collections, such specimens are virtually impossible to identify. They should not be confused with other species or cast into the subgenus Hyalommina. Among collections of reared adults, gradations from typical males to atypical males closely approximating exceptionally small specimens of H. dromedarii are frequently seen. Such atypical specimens are obviously poorly nourished in the immature stages and show numerous indications of lack of proper development. If encountered singly, they would be most difficult or impossible to properly identify. |