The presence of the ventral paired organ related the subgenus Carios to the subgenus Chiropterargas and separates Carios from the subgenus Argas and from other subgenera. The presence of a lateral suture and of peripherally differentiated integument, and the absence of an appendagelike hood clearly separates the subgenus Carios from the subgenus Chiropterargas.

The name vespertilionis was assigned by Latreille in 1802, not in 1796 as stated by most authors. The reference to this name as of 179% (Hoogstraal 1955B) derives from an editorial change.

Schulze (1943B) noted that the immature stages of species of this group ("A. pipistrellae") have especially highly devel oped terminal branching of midgut diverticula but little basal branching.

IDENTIFICATION

Males and females are alike except that males average some what smaller in size and their genital aperture is semicircular in outline, rather than narrowly ovoid, and is not bounded by thickened rugose lips as in females.

In both sexes and in nymphs, a definite lateral suture en circles the body, a dorsal and ventral row of rectangular "cells" marks the body periphery, no appendagelike hood is present over the mouthparts, but ventral paired organs are present just posterior of the anus.

The body outline is generally circular or subcircular, but may be somewhat longer or wider in some specimens. Few individuals reach six millimeters in length or breadth. The integument is smooth, marked by a fine network of small, irregular cells among which regular, subparallel rows of larger discs radiate.

Legs arise from the anterior half of the body and are shorter than the body; coxae are contiguous; and tarsi are tapered and lack dorsal humps.

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 dis tinct differences from A. vespertilionis, to which it is probably more or less closely allied, and from all other described species. This larva was collected from a Pachyotus bat at Latome, Equatoria Province, on 18 March 1951 by Mr. J. Owen.

ORNI THODOROS*

INTRODUCTION

Both important African species of Ornithodoros, O. moubata and O. savignyi, occur in certain areas of the Sudan, where they are known as haim ( ). 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. O. 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. fore, usually found only in their resting places.

They are, there-
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 ran'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 purposes, 0. moubata and O. 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 0. foleyi, O. delanoei 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 O. 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 penguin inhabited islands off Cape Province. Found on Cargados Carajos Island in Indian Ocean (Neumann 1907). 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).