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Mouthparts are situated close to the anterior margin of the body. The hypostome formula is 2/2 to 2.5/2.5, the apex is notched and bears a corona of three or four rows of small denticles in four to six files.

The larval and nymphal illustrations and descriptions of A. vespertilionis by Neumann (1896) are quite good, though they shall have to be expanded for present day purposes.

These have been employed subsequently by the same author, Nuttall et al (1908), Bedford (1934), and others.

ARGAS SP.

(Not illustrated)

A single damaged larva, mounted on a slide, sent by Mr. E. T. M. Reid of the Sudan Veterinary Service, represents an un known species of tick, Although many of the characters of this specimen are obliterated, enough are preserved to indicate distinct differences from A. vespertilionis, to which it is probably more or less closely allied, and from alí other described species. This larva was collected from a Pachyotus bat at Latome, Equatoria Province, on 18 March 1951 by Mr. J. Owen.

ORN I THODOROS*

INTRODUCTION

Both important African species of Ornithodoros, 0. moubata and 0. savignyi, occur in certain areas of the Sudan, where they are known as haim (O). From two to five other species indubitably exist in the Sudan but have not yet been found there. Approximately fifty species comprise the genus throughout the world. 0. moubata is the most important tick vector of relapsing fever in Africa and its bite is often painful. 0. savignyi has been sus. pected to be a relapsing fever vector, although incriminating evidence in nature is negative or unconvincing.

Ornithodoros ticks are thick, leathery, and podlike. They may be more or less difficult to find but pain when they bite signifies their presence. In contrast to Argas ticks, which usually parasitize birds and bats, most Ornithodoros ticks parasitize mammals, including bats, and only exceptionally attack birds, reptiles and amphibians,

The two species under consideration represent a somewhat more advanced stage in evolution of parasitism than do Argas and other Ornithodoros species in that their larvae remain in the large, leathery egg until ready to make the larval nymphal molt. The safety of the tough egg capsule affords delicate larvae considerable protection from the elements. 0. moubata and 0. savignyi are un usual in this respect; larvae of most other Ornithodoros species are active and feed from animal hosts. Shortly after hatching larvae molt to nymphs that soon set out to find a host. Nymphs and adults feed rapidly, in a matter of a few minutes to an hour or two, and are seldom transported while feeding on the host. They are, therefore, usually found only in their resting places. Ornithodoros

*Some writers replace the os ending used here by us. The original name used by Koch (1844) was spelled with an os ending, and this is generally though not universally conceded to conform to the rules of nomenclature and of philology. This question has been reviewed by Najera (1951).

ticks are able to withstand long periods of starvation and are very resistant to aridity. The two species discussed in the following pages have been widely spread along man's trade routes.

Subgenera of Ornithodoros are scarcely better established than those of Argas. 0. moubata and 0. savignyi are closely related species with only one other kindred kind, o. eremicus Cooley and Kohls, 1941, of Utah, western North America. Some workers would include only these three species in the genus Ornithodoros and all others in several different genera. This position seems an unnatural approach and a useless complexity. For present pur. poses, 0. moubata and 0. savignyi are treated as in the subgenus Ornithodoros, the only one presently known to be represented in the Sudan.

In addition to these two tampans, it is certain that several other species of Ornithodoros occur in the Sudan and await dis_ covery, Among these should be o. foleyi, O. delanoči subsp., and possibly some member of?the 0. Tholozani group. When more inten sive search is undertaken in the Sudan it will probably be found that 0. erraticus is localized but widely distributed here. 0. erraticus is broadly characterized by small size (maximum length 7.5 mm., usual length 3.0 to 5.0 mm.), oval shape, closely crowded, hemispherical granulations interspersed by large discs, and absence of tarsal armature and of cheeks surrounding the mouthparts. Specimens will probably be found in small mammal burrows.

The following are the other known Ornithodoros species that occur in Africa, with selected references concerning them:

0. arenicolous Hoogstraal, 1953 (c); description of all stages;

biology; from rodent, hedgehog, and Varanus lizard burrows in Egyptian deserts. Absence of spirochetes (Davis and Hoogstraal 1954).

0. capensis Neumann, 1901; described from penguininhabited islands

off Cape Province. Found on Cargados Carajos Island in Indian
Ocean (Neumann 19078). Challenger Expedition specimens from
St. Paul's Rocks (Nuttall et al 1908). Present on islands off
Southwest Africa (Tromsdorff 1914). Biology of hosts and
description of habitat, St. Croix Island off Cape Province
(Hewitt 1920). Other South African records (Bedford 1934).

Records from western Australia (Taylor and Murray 1946). Present on marine birds, Guam (Kohis 1953). Specimen from leg of soldier on island in Lake Nyasa (Hoogstraal 19540).

0. coniceps (Canestrini, 1890); described from Venice, Italy.

Specimens, from near Aral Sea, in St. Petersburg Museum
(Birula 1895); these quoted by Yakimov and Kohl-Yakimov
(1911) and Yakimov (1917,1922). Present in France (Guitel
1918, Theodor 1932, Roman and Nalin 1948). As 0. talaje
from Fezzan, Morocco; introduced with pigeons; severe se
quelae in human victims (Martial and Senevet 1921). From
bats and pigeons, life cycle, Tunis (Colas Belcour 1929).
Description of all stages, Palestine (Theodor 1932). Bi.
ology, Palestine (Bodenheimer 1934). Present in Spain
(Gil Collado 1947,1948A,B). Present in Morocco (Blanc and
Maurice 1950). Present in Nablus area of Jordan; parasite
of chickens and persons; infected with spirochetes (Badu
dieri 1954,1955). Transmits fowl spirochetes ("Brumpt's

Precis"). Life cycle (Davis and Mavros 19560). 0. delanolei delanoei Roubaud and Colas_Belcour, 1931; described

from porcupine burrow, Morocco. Biology (Roubaud and Colas.. Belcour 1936). Life cycle and larval feeding (Colas_Belcour 1941). Non_transmission of spirochetes (colas-Belcour and Vervent 1949). Present in Egypt (Hoogstraal 1953C). Ab_ sence of spirochetes (Davis and Hoogstraal 1954). Life cycle (Davis and Mavros 1956A). Biological observations and dis tribution in Egypt; descriptions of immature stages (Hoogstraal 1955E).

IK

delanoei acinus Whittick, 1938; described from cave in British

Somaliland. Haemoglobin (Wigglesworth 1943). Biology (Ro-
binson 1946). Coxal organs ("glands's) (Lees 1946B). Trans-
piration from cuticle (Lees 1948). Egg waxing organ (Lees
and Beament 1948). Weight of tick and of its cuticle, fed
and unfed (Lees 1952). Larval and nymphal measurements,
and the increase in size following each molt and male meas.
urements have been noted by Campana Rouget (1954).

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