297 



While the Ixodinae only moult twice during their 

 life, viz., at the change from larva to nymph, and again 

 from nymph to adult ; the Argasinae moult not only 

 at these periods but also several times during the 

 nymphal stage and again several times during the 

 adult stage. The Argasinae also do not become 

 distended with blood to the enormous extent so 

 characteristic of the Ixodinae. The duration of life 

 is probably a year or more. 



EXTERNAL ANATOMY 

 IXODINAE 



The Rostrum or Capitulum. The rostrum consists 

 of a massive posterior portion (head) prolonged 

 anteriorly into the mouth parts. 



The dorsal surface of the head is continuous, 

 anteriorly, with two tubular sheaths (mandibular 

 sheaths) within which the rod-like mandibles (or 

 Cheliceres) play (Fig. 95). Ventrally, the head is 

 continued forwards as a conspicuous dagger-shaped 



Cheliceres 



Pedipalps 



Pedipalps 



ig- 95- (Left figure}. Mouth -parts of Hyalomma (an Ixodine). 

 (Right figure] Mouth parts of an Eurhipicephalus (a Rhipicephaline) 

 H = hypostome ; 1-4 = segments of palpi 



