374 THE ANIMAL PARASITES OF MAN 



Ornithodorus megnini (Duges), 1883. 

 Syn. : Argas megnini, Duges, 1883. 



Length 8'5 mm., breadth 5*5 mm. Native of Mexico. 1 



[Another synonym for this species is Rhynchoprion spinosum, 

 Marx. Wheler describes the nymph as follows : Length 3 mm. to 

 4 mm. fasting, to 9 mm. when replete. Body brown, diamond shaped, 

 with the rostrum exposed before repletion. Rostrum beneath the 

 body and the latter squarer after distension. Palpi filiform. Legs far 

 apart and coxae almost entirely concealed beneath the skin. Surface 

 of the anterior half of body covered with small brown spines, 

 replaced by whitish hairs posteriorly, which are specially numerous 

 in the hinder margin. The stigmata are placed above instead of 

 behind the fourth pair of- legs. These differ entirely from the stigmal 

 plates and peritremes usually present, and consist of cone-like pro- 

 jections pointing backwards. The top is truncated and perforated 

 by an orifice ; through this is a jointed organ, somewhat resembling 

 the terminal joints of the palpi, which partially fills the orifice and 

 is furnished with three hairs at the end. It can be projected and 

 withdrawn with rapidity. This feature, according to Neumann, is 

 absent in the male. The female is stated by Neumann to differ 

 greatly from the nymph, which latter attains dimensions at least as 

 large as the mature adult. 



Two specimens in the nymphal state were taken from the ear of 

 an American visitor to Cambridge by Dr. J. Christian Simpson. 

 They were supposed to have entered the ear when the American 

 was camping out in Arizona. 



This species attacks the horse, ass and ox, generally around 

 the ears, but it chiefly attacks man. It is well known in the 

 United States as infesting the ears of children (New York Ent. Soc. 

 Journ., pp. 49-52, 1893). F. V. T.] 



7. Fam. Tyroglyphidce. 



Very small mites without eyes and without tracheae,- with smooth skin. 



The males usually have a suctorial pore on either side of the anus, which 



is used during copulation, or suckers may be found in both sexes near the 



1 Duges, A., La Naturaleza, Mexico, 1883, v., p. 195; Megnin, P., " Les Argas 

 de Mexique " (Journ. de Van et de la phys., 1885, xxi., p. 460) ; Neumann, G., I.e., 1896, 

 p. 42 ; Guerin, in Bull. soc. chir., 1867, viii., p. 444 ; Simpson, J. Ch., " Case of Para- 

 site (Arg. Megn.) in each ear " (Lancet, 1901, No. 17, p. 1197). 



2 [Cheyletus has a distinct and peculiar tracheal system. F. V. T.] 



