496 THE ANIMAL PARASITES OF MAN 



now known as Rhipicephalus annulatus, Say (the carrier of Texas 

 fever), moulting takes place on the host, and in many other species 

 also. 1 Some species of ticks leave their host on its death (as the dog 

 tick, Hcemaphysalis leachi), but others die with the host (bont tick, 

 Amblyomma hebrceuin}. 



[Two species are of special importance, namely Ornithodorus 

 moubata, Murray, which may infect human beings with the spirillum 

 of African tick fever, and Dermatocentor reticulatus var. occidental^, 

 which is said to be the carrier of Rocky Mountain spotted fever. 



CLASSIFICATION OF Ixodidcv. 



[The TICKS, or Ixodida, are divided into two groups, known as 

 (i) Argantince, (2) Ixodince. The Argantince are told from the 

 Ixodince by the absence of dorsal or ventral shields in both sexes, 

 and also by the rostrum being placed beneath the cephalothorax, 

 which covers it over : except in the larval stage, in which it is sub- 

 terminal, and in the pupal, when it partly projects. Legs nearly 

 equal in length. The sexual orifice is situated between the two first 

 pairs of legs. The males usually smaller than the females. 



[The Ixodince have the legs unequal, of six segments with two 

 false segments, making them look as if composed of eight segments. 

 The rostrum is terminal and never hidden beneath the body. 

 The sexual orifice is situated between the bases of the first three 

 pairs of legs. In the males the orifice is obsolete or very rudi- 

 mentary, sexual intercourse being effected by the rostrum. The 

 males are smaller than the females. The shield in the females never 

 covers so much as one-half of the body even when fasting, also 

 in the larvae and nymphs ; but in the males, which do not distend, 

 the shield covers the body entirely, or all but a narrow margin. 

 The Ixodince are divided into two groups : (i) the Ixodce, and (ii) the 

 Rhipicephalce. The former have a long proboscis reaching nearly to 

 the end of the palpi or even a little longer than the palpi. The 

 palpi are longer than broad. The Rhipicephalce have short palpi, 

 nearly or quite as broad as long, more or less conical or subtriangular. 

 They were called Conipalpi by Canestrini. 



SYNOPSIS OF GENERA. 



[A. Argantince : Rostrum concealed in adult, partly exposed in 



larvae and nymphs. No dorsal and ventral shields. 

 Body flat with thin edges, finely shagreened and punctate Argas. 

 Body with numerous small round granules and with thick 



sides ... ... ... ... ... ... ... ... Ornithodorus. 



1 Some ticks require only one (R. decoloratits}, others two (R. evertsi}, and some 

 three hosts (R. appendiculatiis] in order to reach maturity. 



