Leeson 1953. Theiler and Robinson 1954. Theiler and Hoogstraal 1955). UNION OF SOUTH AFRICA Lounsbury 1899 1900B,C (confused with 0. moubata), 1903B,1904A. Howard 1908. Donitz 1910B. Bed ford 1920,1926,1927,1932B,1934. Alexander 1931. Bedford and Graf 1934,1939. R. du Toit 1942B,C,1947A,B. Theiler and Robin son 1954. Theiler and Hoogstraal 1955.7

NEAR EAST: ADEN (Nuttall et al 1908. Patton and Cragg 1913. Cunliffe 1922. Hoogstraal ms.T. YEMEN (Mount 1953. Hoogstraal, ms.). PALESTINE (Theodor 1932. Smith 1936 quoted by Brumpt 1936. Bodenheimer 1937). IRAQ (Leeson 1953).

MIDDLE EAST: INDIA (Christophers 1906. Neumann 1911. Patton and Cragg 1913. Donovan 1913. Fletcher 1916. Cross and Patel 1922. Rao and Ayyar 1931. Sen 1938. Sharif 1938. Kapur 1940. Joshi 1943). CEYLON (Nuttall et al 1908. Brumpt 1936. Crawford 1937. Chow, Thevas agayam, and Tharumarajah 1954).

HOSTS

Camels are most frequently mentioned as hosts. 0. savignyi appears to be present in most areas in which dromedaries are used. Fowls are sometimes attacked and all domestic animals may serve as hosts (Lounsbury 1900B). For instance, this tampan is common in cattle yards at Mawar, India (Joshi 1943) and under trees where mules are tethered in Somaliland (Lipparoni 1951). Human beings are frequently bitten, especially when they sleep in camel yards or sit under trees commonly used by domestic animals for shade. Any laboratory animal may serve as a host. Dogs are satisfactory laboratory hosts (Lounsbury 1904A).

Game animals are said to be attacked, but evidence is scant. The rhinoceros, lion, and buffalo may serve as hosts in Kenya according to Walton (1951). Neumann (1912) reported numerous specimens from a Kenya locality where a giraffe had been standing.

BIOLOGY

Life Cycle

Eggs of 0. savignyi are deposited in sandy soil where adults hide. Individual females, observed by Cunliffe (1922) at 30°C.,

laid from 100 to 417 eggs, averaging 219. Other individuals that had fed four times laid five egg batches totalling about 900 eggs over a thirteen month period (Patton and Cragg 1913). The embryonic development, described by Christophers (1906), is essentially like that of O.moubata.

Larvae, like those of 0. moubata, are nonmotile and do not feed. Although some undergo ecdysis in the egg, most larvae free themselves from the eggshell before molting to nymphs (Cunliffe 1922). After splitting the eggshell, larvae molt to nymphs in five hours (Davis 1947) to ten hours (Patton and Cragg 1913).

Four nymphal instars over a period of about 84 days and seven nymphal feedings were observed by Patton and Cragg (1913). Cun liffe (1922), on the other hand, noted that males appeared after four to six molts and females usually after the sixth molt. Rea sons for differences in mumber of instars among argasids remain to be ascertained.

The very active nymphs commence feeding two or three days after molting and require fifteen to thirty minutes to reach repletion. Adults normally feed for similar periods but the presence of both stages along remote camel trails would indicate that on occasion some tampans may remain longer on the host.

Females in Cunliffe's (1922) studies lived between 292 and 420 days at 30°C. and for an average of 775 days at 22°C.

Spermatophores superficially similar to those of 0. moubata are utilized by this species (in Egypt), although Christophers (1906) and Nuttall and Merriman (1911) questioned their presence.

Other details of the life cycle have been reported by the above mentioned observers and by Rousselot (1953B). However, more extensive and refined studies are still necessary.

Ecology

0. savignyi, among the tick species studied by Lees (1947), shows the greatest ability to limit water loss at high temperatures. The critical level for this species is 75°C. while for O. moubata

it is 63°C. Even xerophilic hyalommas abruptly increase water loss at 45°C. (cf. page 154). This factor explains in part how the eyed tampan can exist in deserts where little other life is sustained. Cunliffe's (1922) studies, from which he concluded that the temperature and humidity requirements of both these tampans are much the same, should be repeated with special at tention to extreme levels.

Famous for the viciousness of its attack, this tampan is usually well known wherever it occurs. Natives quickly lead one to infested animal corrals, trees under which man and beasts rest, and well sides where the eyed tampan is superficially burrowed awaiting its prey. In Somaliland, Lipparoni (1951) reported, 0. savignyi is common under trees where soldiers tether their mules and 0. moubata infests huts beside these trees. Although the adventitious presence of 0. savignyi in buildings must be expected, early records from human habitations appear to be based on misidentification. For instance, Drake Brockman's various reports of 0. savignyi in British Somaliland buildings have been questioned by Anderson (1947). Anderson found O. savignyi exclusively outdoors in the same area, and O. moubata, previously thought to be nonexistant in the area, exceedingly common in huts and coffee houses.

We have never observed 0. savignyi in sites directly exposed to the sun. Indeed, at the Khartoum quarantine one may see a long, seething line of thousands of hungry tampans helplessly confined to the shade of a row of acacia trees. A few yards away, separated only by the hot, nine o'clock sun, newly arrived cattle tied to a post fence tempt the tampans to cross the glaring strip. The next morning, in the coolness of seven o'clock, those tampans under the trees are all blood bloated and resting comfortably in the sand, others are dragging back from their hosts across the now nonexistant barrier, and the legs of the cattle are beaded with yet other podshaped ticks taking their fill of blood in a regular line just above the hoof.

Laboratory rats and mice, as noted by Heisch (1950A), assail this tampan. Rats feast on nymphs and adults. Mice commonly assault nymphs, but only particularly bold mice attack adults. These rodents, in turn, facilely escape bloodthirsty but lumbering adults, although small, active nymphs more easily attack them. Predators in nature do not appear to have been reported.

REMARKS

Christophers (1906) extensive study on morphology and diges tion of 0. savignyi has been reviewed in the section on 0. moubata, which also contains a number of other data pertaining to both species.

The nymphal instars may be approximately determined according to Cunliffe's (1922) data, also presented by Campana Rouget (1954).

The haller's organ of O. savignyi has been described and il lustrated (Schulze 1941).

Jakob (1924) used this tampan to illustrate certain theories separating the ixodids from the argasids on the basis of differences in external grooves, ridges, and prominences. He did not believe, as a result of these studies, that Argas developed from Ornithodoros, but rather that both genera had a common origin in the Uropodidae, a member of which, Discopoma africana Vitzhum, was illustrated.

DISEASE RELATIONS

MAN. The bite of 0. savignyi may have severely painful seque lae but this tampan has never been found infected with pathogenic organisms in nature, and transmission of pathogens has not been demonstrated until recently. Even the earlier assertions that the eyed tampan transmits human relapsing fever (Borrelia spp.) have been cast into considerable doubt by subsequent research.

DOMESTIC ANIMALS. Camels and cattle suffer greatly and may even be killed by the volume of blood lost to numbers of eyed tampans in their pens.

EXPERIMENTAL. Leishmania donovani, which causes kala azar in human beings, does not develop in 0. savignyi. Trypanosoma cruzi undergoes development in this tick in the laboratory. T. evansi cannot be transmitted from the tick to animals except by inocula tion of a suspension of infected ticks.

Experiments on transmission of heartwater (Rickettsia ruminan tium) of cattle by means of O. savignyi have been unsuccessful.

West Nile virus remains viable for at least three months in 0. savignyi, and transmission of the virus to mice by the bite of parenterally-infected ticks has been demonstrated. Similarly, specimens experimentally infected with Sindbis virus transmit the organism when biting.

Spirochetosis of chickens (Borrelia anserina) is not trans mitted by this tampan.

IDENTIFICATION

See remarks under 0. moubata, pages 189 and 190.