MIDDLE FAST: INDIA AS H. kumari: Sharif (1928,1930). Delpy (19498) considers H. kumari as a synonym of H. excavatum but it seems best to reserve judgement on this matter for the moment. Numerous specimens typical of H. excavatum are present in BMNH collections, H.H. det. As H. savignyi: Dasgupta (1955) and Dasgupta and Ray (1955); the possibility that these refer to H. marginatum should be considered. PORTUGESE INDIA (Santos Dias 19543).

HOST'S

H. excavatum is a parasite of cattle, horses, donkeys, camels, buffaloes, sheep, goats, and swine. It also attacks man and dogs. Hares appear to be especially important wild hosts.

Nymphs are variable in occurrence on cattle, but nymphs and larvae are often found on calves. Nymphs and larvae frequently attack rodents, and normally do so on the desert. They also feed on man, hares, lizards, and birds.

All stages of H. excavatum have been observed feeding on hares in a forest near Casablanca where other wild and domestic animals are absent (Blanc and Bruneau 1953,1954,1955). In Ana tolia, numerous adults have been reared from nymphs taken from hares (Hoogstraal, ms.). A larva has been reported from a hare in Iraq (Hubbard 1955). In Yemen these animals are heavily infested by immature stages (Hoogstraal, ms.). British Museum (Natural History) collections contain specimens from Indian hares (Nuttall lot 3423; H.H. det.). Wherever hares and H. excavatum occur together the association appears to be an important one.

The complete absence of any specimens of H. excavatum on more than five hundred hedgehogs collected throughout Egypt, is noteworthy (Hoogstraal, ms.). Hedgehogs were, however, used as laboratory hosts of immature stages by Feldman Muhsam (1948).

Delpy (1949C) considers birds, especially nestlings, important hosts of nymphs. A male in British Museum (Natural History) collections has been reared from a redstart, P. phoenicurus (= Ruticilla pluvenicurus) at Amara on the Tigris River (Nuttall lot 3240; H.H. det.).

Single instances of attack of human beings have been reported from France (Buttner 1949) and Iraq (Hubbard 1955; whether actual ly feeding not stated). During field work for the present study, feeding specimens of H. excavatum have been taken from personnel in Egypt, Turkey, and Yemen (Hoogstraal, ms.). In Uzbekistan, this tick (= H. anatolicum) often attaches to man (Gajdusek 1953).

Apparently the only larger wild animals yet recorded as hosts of the adult stage are gazelles in French Somaliland (Hoogstraal 1953E).

Biological observations in Egypt thus far have been confined to searching for naturally infested wild animals in the field, keeping them alive in the laboratory, and allowing ticks that drop from them to molt to the next stage. Adults reared from nymphs taken from wild animals have been from the following hosts:

Colas Belcour and Rageau (1951) report adults in Tunisia from burrows of gerbils, jirds, and fat sandrats and nymphs from jirds. They also found H. excavatum in burrows and on other rodents in France. Adults of H. excavatum in rodent burrows are always newly molted, remaining there before they venture forth to seek a larger host (Hoogstraal, ms.). There is no evidence to consider gerbils as common hosts of adults, as stated on the map of the American Geographical Society (1954); see also Erratum sheet).

BIOLOGY

Life Cycle

The several investigators who have reared H. excavatum in the laboratory (Delpy 1952 in Iran; Daubney and Said 1951 in Egypt;

Feldman Muhsam 1948 in Palestine; Brumpt and Chabaud 1947 in France, and Serdyukova 1946A in Russia) confirm that this is normally a three-host species. In Tadzhikistan, however, Lotot sky and Pokrovsky (1946) consider H. excavatum (= H. anatolicum) to be a two host tick. Feldman Muhsam observed that some larvae may remain on the host through the nymphal stage, but Delpy (19460) stated that if they do so, they first detach and wander away, for example to the ear, and reattach only after molting. Daubney and Said observed a single larva molting while still attached. On desert rodents in Egypt nymphal H. excavatum have on several occasions been found attached to the host and partially enclosed by the larval exuvia. Possibly in these situa tions, where hosts are scarce, the typical life cycle is more commonly somewhat altered. On Egyptian deserts, the molt from nymphal to adult stage typically occurs in rodent burrows. Remarks that desert rodents dislodge most ticks attached to them by rubbing, shaking, or eating are contrary to frequent experience in Egypt.

The effect of a small size host on the life cycle of H. excavatum has perhaps best been described by Serdyukova (1946A, as H. anatolicum) (from abstract in Review of Applied Entomology):

"Larvae from a single egg-batch engorged on a
rabbit, which is an unusual host for this tick. Some
detached after engorgement, others molted on the ani
mal. Some of the resulting nymphs wandered on the
rabbit without feeding but others engorged and then
dropped off. Larvae placed on the ears of a calf all
detached after engorging, and no engorged or molting
larvae or larval exuvia were observed on calves in
the field. Ticks collected in a calf shed included
freshly engorged and molting larvae and unfed nymphs.
It is concluded, therefore, that H. excavatum = H.
anatolicum) develops as a three host tick on its
normal host, but that an unusual host may alter this
behavior. The cycle of ixodid development has prob
ably altered as a result of evolutionary processes.
The type of development that occurs on the usual
host should be considered as normal, and deviations
from it on unusual hosts as atavistic."

It is significant that the Russian worker considers the rabbit to be an atypical host of immature stages of H. excavatum. This is far from true in North Africa and Arabia, where hares and other smaller animals are frequently parasitized (rabbits do not occur here). Most probably smaller animals are also parasitized in Russia but workers there, who have been occupied chiefly with veterinary problems, have failed to investigate this possibility. Indeed, it seems that a diametrically opposed, theoretical con clusion might be drawn:

Under primitive conditions, in areas lacking large
numbers of domestic animals, H. excavatum spends part
or all of its life cycle on small animals, usually no
larger than hares. In these situations it undergoes a
one or two host type of life cycle. However, when herds
of larger domestic animals are present in the range of
this tick, the adults and sometimes the immature stages
may be confined to these animals. On these larger ani
mals, H. excavatum undergoes a three-host type of life
cycle, which is an atypical one for the species, in
fluenced as it is by the availability of hosts due to
human activities.

This matter is obviously in need of further investigation.

With regard to the seasonal cycle of H. excavatum, the aforementioned authors working in Iran, Egypt, and Palestine, as well as Serdyukova (1946B) working in the semi-deserts of Tadzhikstan, agree that engorged nymphs and young adults hi bernate in cracks and crevices of buildings during the winter; the Soviet observer states that larvae may also overwinter under these conditions. In Russid, hibernating ticks were taken in, among, under, and in association with wooden fixtures of animal enclosures, but not under cakes of dung plastered on loose walls. When these structures were removed the incidence of ticks found in these yards the following summer was only a fraction of what it had been the previous year. In the deserts of Egypt engorged nymphs and unfed adults overwinter in rodent burrows.

In spring, ticks that have hibernated venture forth to feed. Under experimental conditions, if they are removed to a warmer

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 32oC. 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 Perva 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