place during the winter nymphs molt and adults feed. In Egypt, wild nymphs do not normally molt until almost summertime, possibly because of cold nights during early spring. By late March, however, females begin to feed, and at this time they may oviposit very shortly after dropping from the host as soon as seven days afterwards. The incubation period may be as short as 27 days, so that in May new larvae and last year's nymphs can be found feeding. Under the Russian conditions already mentioned, oviposition does not commence until July or August and it appears that there is only a single generation a year in those climes. In Tadzhikistan (Lototsky and Pokrovsky 1946), adults of H. excavatum (= H. anatolicum) infest cattle from the end of February to November, and larvae and nymphs from July through September; all stages are most numerous early in August.

Larvae feed for from four to six days (32°C., 75% R.H.) according to Feldman Muhsam, but the Russian observer reported only two to four days in nature. Larvae molted six days after leaving the host (30°C.), after four or five days at 38°C., and after thirty to fifty days at 17.5°C. (after six to twelve days in Russian observations). Nymphs fed a week later and remained on the host from nine to twelve days (four to six days in Russia) but the time between dropping and molting to the adult stage varied greatly (twelve to twenty days in Russia).

At 35°C., the molt to females occurred in from eleven to 24 days and to males in from twelve to 35 days. At 30°C. both sexes appeared between eleven and 56 days after nymphs dropped from their host. The duration of one generation at 32°C. was estimated at 116 days, but it was concluded that under field conditions some of these stages may be shorter and there may be three generations a year.

Parthenogenesis in H. excavatum has been observed by Pervo maisky (1949) who found that a few F1 females could be reared from eggs laid by females in the absence of males.

Ecology

Feldman Muhsam (1947) observed that unfed larvae and nymphs are much more sensitive to humidity than to temperature. At any

temperature survival of unfed immature stages increases with higher humidity. In laboratory tests, larval longevity varied between two and 241 days (mean 1.25 and 162.6 days), nymphal longevity between ten and 246 days (mean 6.8 and 149.2 days). The author considered that under undisturbed natural conditions survival would have been longer than in these tests in which daily counts were made.

Nymphs are less susceptible than larvae to low humidity. The length of nymphal life increases directly with humidity and inversely with temperature. Other life history and hibernation studies by Feldman Muhsam (1949) are of interest, but since they apply to frigid Palestinian winter conditions that do not occur in the area under consideration this work is not presently pertinent.

Serdyukova (1946A) observed ticks detaching from their hosts at night; larvae and nymphs mostly between nine and eleven o'clock in the evening. A number of larvae and nymphs placed on a calf in the morning became fully engorged during the day but remained on the calf when darkness set in. This behavior, probably an adaptation to local climatic conditions, protects the ticks from exposure to the direct rays of the sun, which are fatal to them. They are apparently inactive during the hot part of the day, and attach to hosts at night as has been recorded for other Hyalomma species under desert conditions. In an isolated plot only slightly over five percent of a counted number of unfed ticks attached to calves between noon and sunset.

H. excavatum is obviously a tick of xeric regions not neces sarily associated with domestic animals although populations are considerably larger where these animals occur. Experience in the comparatively lightly-vegetated desert areas of the Mediterranean littoral of Egypt, where it infests rodents in their burrows, indicate this tick's habits away from large, dense flocks of domestic animals.

In Transcaucasia, H. excavatum (= H. anatolicum) is typical of various desert, semidesert, and steppe formations, but does not occur in forested zones (Pomerantzev, Matikashvily, and Lototsky 1940). This agrees with observations in Anatolia (Hoogstraal, ms.). With respect to altitudinal distribution in Trans

caucasia, these authors say H. excavatum falls in group in which the "upper limit of distribution is ..... inversely proportionate to the moisture of the climate and to the amount of rainfall and directly proportionate to the height of the snow line during the summer period".

In Armenia, H. excavatum (= H. savignyi armenorium) is found in pasture at 6500 feet elevation and higher (Lototsky and Popov 1934). During the present study it has been found at similar heights in Sinai, Yemen, Anatolia, and Eritrea.

Feeding Sites and Reactions

Adults feed on cattle chiefly on the scrotum and perineum and in the inguinal and axillary areas. Nymphs generally feed on the neck, chiefly along its crest. Larvae are not commonly found on Egyptian cattle.

Note: The following section is ancillary to further remarks on the subgenus Hyalommina" (page

In Egypt (Hoogstraal, ms.), larvae and nymphs of H. excavatum are frequently found completely overgrown by rodent host skin. This phenomenon is especially common among young jirds, Meriones shawi shawi Duvernoy, and sometimes on young fat sandrats, Psammo mys o. obesus, on the Mediterranean littoral. During springtime almost every nestling jird in the vicinity of Mersa Matruh is infested in this manner. The ticks can be detected by lumps under the skin, most frequently around the neck, axillary areas, shoul ders, and flanks. Some of these rodents have as many as 22 im mature ticks under the skin. The host skin may partially or completely enclose the ticks*, which are almost always misshapen when removed. Some nymphs extricated from under the skin of jirds have molted to adults in our laboratories. They have in variably been tiny, weak, misshapen, poorly developed, pale specimens, which, if identified according to criteria offered by Schulze (1919), would be H. rhipicephaloides Neumann, 1901, in the subgenus Hyalommina.

*Nuttall (1914B) has quite accurately described this processes as an oedematous swelling of the host skin, as a result of irritation when the long mouthparts of Ixodes (and Hyalomma) ticks reach firm subcutaneous connective tissue; the oedematous swelling may gradually engulf the feeding tick.

Schulze (1921) recognized this growth phenomenon for material of "H. rhipicephaloides" from a "steinbock" (probably meaning an ibex) near the Dead Sea in Palestine, although he continued to apply a species name to these runts. Yet, Schulze and Kratz have presumed to refer to this as a "half-endo parasitic type of para sitism" by ticks. Large number of ticks were found in pale reddish cysts in the ibex's subcutaneous tissue, especially in the axillae. Holes in the host skin could not be detected.

In several instances we have found cast larval skins en casing subdermal nymphs. Young jirds raised to adulthood in the laboratory yielded dead H. excavatum in the middle of the summer when the hosts were sacrificed, and nymphal skins were found around them. We have no evidence that a Hyalomma tick overgrown by the host's skin can force its way out through the skin.

Pavlovsky, Pervomaisky, and Chagin (1954), in preliminary studies, have also indicated that when H. excavatum (= H. anato licum) feeds in large numbers on a restricted area of the host, poorly developed specimens result. Females especially do not fully engorge and may even die due to inflammation of the host skin. When other species also compete for a restricted area of the host skin, an additional antagonistic factor increases the chances of abnormal development or death.

Prolonged infestation on rabbits by H. excavatum under lab oratory conditions does not confer host immunity, preventing engorgement by subsequent larvae, against this species or against Dermacentor pictus (Chabaud 1950A, Brumpt and Chabaud 1947).

REMARKS

A capillary tube arrangement, which has proved successful for the artificial feeding of adults of H. excavatum for physio logical and disease transmission studies, has been described by Chabaud (1950A).

Schulze (1932C) illustrated the leg segments (of "H. anatolicum) to support theories of tick ornamentation. In the same

work, he illustrated a cross section of the scutum (of "H. lusita nicum) and compared it with that of A. cohaerens.

Gynandromorphs and malformed specimens of this species have been described and illustrated (as H. savignyi: Pavlovsky 1940) by Pervomaisky (1950). A gynandromorph of H. excavatum (= H. savignyi) has been described by Feldman Muhsam (1950) but Campana Rouget (1950) considers this to be an "intersexue" (see also Chabaud and Choquet 1953). An abnormal male ( (as H. kumari) has been illustrated by Sharif (1940).

The rate of growth and comparative differences among those morphological parts that are either similar or different between the two sexes of this tick have been studied by Chabaud and Choquet (1953). Cuticle growth has been mentioned by Lees (1952, as H. savignyi).

Campaniform sense organs have been briefly described (Das gupta 1955).

Specimens from Kenya, identified as H. anatolicum, were used by Yalvac (1939) to describe features of development of the adult stage in nymphs.

DISEASE RELATIONS

MAN: The virus of Uzbekistan hemorrhagic fever has been isolated from H. excavatum (= H. anatolicum) in Soviet Central Asia, where this tick appears to be at least an important natural reservoir if not a vector. Experimental work with H. excavatum (= H. turkmeniense) indicates, for the virus of Russian spring-summer encephalitis, transmission by bite and transovarial transmission, and the same for the virus of Japanese (mosquito-borne) endephalitis except that transmission by biting was not obtained. These viruses, as well as that of Russian (mosquito-borne) encephalitis, persist for many months in infected ticks.

H. excavatum is commonly found infected with the rickettsiae of Q fever (Coxiella burnetii) in North Africa, southern Europe,