ii6 Veterinary Medicine. 



Anal shields or plates {dypei) are found only in the male of 

 particular genera, which have two on each side of the anus. 



Stigmata {stigmal plates, peritrennes) are situated, one near 

 each margin, between the III and IV legs in Argasidse, and back 

 of the IV pair in Ixodidse in the octopod stage. In Boophilus 

 Annulatus they are present in the larvae as well and may be even 

 in three pairs (Stiles). Each bears its stigmal breathing aperture 

 or spiracle. 



Two Genital Furrows, beginning one on each side of the 

 genital pore, extend backward, and from near the plane of the 

 IV legs diverge to the postero-lateral borders. The Anal Furrow 

 extends backward in the median line. 



The pits, punctations, and hairs have similar characters as 

 on the back. 



A hard chitinous Caudal Appendage characterizes certain 

 species such as Boophilus Australis. 



Leg. These are six in number in larva (hexapod) and eight 

 in nymphcB and adults (octopods). They are indicated as pairs I, 

 II, III and IV. Each leg is made up of six articles united by 

 joints, and from proximal to distal end are named coxa, trochan- 

 ter, femur, tibia, protarsus and tarsus. The coxa, is firmly 

 fixed on the ventral aspect of the body, and may be furnished 

 with one or more spurs ; the others are movable. The distal 

 article (tarsus) is furnished at its free end with two claws and on 

 its lower aspect a disc-like membranous expansion (pulvillum), 

 and a cup-shaped organ (Haller's) which has been supposed to 

 be subservient to the sense of hearing. 



IXODOIDEA. TICKS. 



KEY TO FAMILIES AND GENERA. 



Salmon and Stiles give the ticks as a superfamily , divided into 

 the t^NO families of Argasida and Ixodidce. They give the fol- 

 lowing key to the families , subfamilies and genera ; 



1. Scutum (dorsal plate) absent Argasidae 

 Scutum present Ixodidse 



Family Argasid^E. 



2. Capitulum removed by at least its length from the anterior 



margin : body rounded anteriorly, without a projecting 

 beak-like prominence ; eyes absent. Argas 



