580 MEDICAL ENTOMOLOGY 



* 



The Argatini contains two genera, Argas and Ornithodorus, the species 

 of which are characterised by the flat shape of their bodies and the ventral 



position of the capitulum ; in the larval stage the latter 

 General Structure . . , . , , , 



Plate LXXXIV mav " e terminal or sub-terminal. On the ventral surrace 



of the adult there are two folds, one internal to the 

 coxae, the coxal fold, and the other above the coxae, the supracoxal fold. 

 The base of the capitulum is rectangular and is attached dorsally to the 

 surface of the cephalothorax ; the hypostome is broader at its base than at 

 its apex, and is nearly always armed with a smaller number of teeth than 

 is usually found in the Ixodini. The articles of the mandibles are more 

 delicate than those of the Ixodini. The four segments of the palps are 

 cylindrical and leg-like, and are all about the same length. The eyes, which 

 are present only in some species of Ornithodonts, are arranged in one or 

 two pairs situated in the supracoxal fold. The spiracles are discoidal or 

 reniform in shape. The legs are of medium length and the coxae are 

 always devoid of spurs ; the tarsi and protarsi frequently have marked 

 protuberances. The male is usually a little smaller than the female, 

 otherwise they are much alike. The genital aperture in both sexes is 

 situated in the interval between legs I and II. In the male it is narrow 

 and almost as long as it is broad, and is semi-lunar in shape ; in the 

 female it is a wide transverse slit with more or less parallel borders ; 

 it is almost as broad as the base of the rostrum. 



GENUS ARGAS, LATREILLE 



Body flat, oval or rounded in contour, with a flattened margin giving it 

 a sharp edge which is apparent even when the tick is replete with blood. 

 The body is often narrowest in front and may even be pointed. The 

 integument is not mammillated, but has on the dorsum and venter symmetri- 

 cally arranged discs usually disposed in radial lines ; the remainder of the 

 skin is wrinkled into irregular folds. The coxal and supracoxal folds are 

 prominent. Eyes are absent. (Neumann) 



According to Neumann the genus Argas consists of nine well estab- 

 lished species, one doubtful and two separated into four sub-species. He 

 gives the following key for the identification of the species. 



NEUMANN'S KEY TO THE SPECIES OF ARGAS 



1. Body at sides convex, without pointed anterior end . . . ; ,' . 2 

 Body at sides rectangular, parallel, with anterior end blunt .... 8 



2. Body oval, longer than broad, straighter anteriorly 3 



Body discoidal, or circular, broader anteriorly . . . vespertilionis. 



(France ; England ; Germany ; Egypt ; Algeria ; S. India.) 



