341 



Ixodidae open into a stigmal plate or peritreme. 

 In the Argasidae they lie between the third and 

 fourth legs. The shape of the plates are important 

 in classification. 



ID. The Anus is a little way in front of the 

 posterior ventral margin. It has a valve. 



11. The Anal plates or clypei, four in number, 

 on either side of the anus, in the male. They are 

 used for classifying. Not always present. 



12. The genital orifice is in the middle line, 

 a little way behind the rostrum. 



13. The Legs are six in the larva, eight 

 in the nymphs and adult. The claws have 

 ventrally a well-marked pad or pulvillum. The 

 coxa (with which the trochanter articulates) may 

 have spines or teeth or larger ' shields.' These are 

 used in classification. 



Internal Anatomy and Dissection of Ticks 



1. Take a large gravid female which has 

 been kept a few days until it shews signs of 

 shrinkage. 



2. Taking care not to compress the tick, snip 

 tangentially round the body. 



3. Place the tick in normal saline, and now 

 separate the dorsal from the ventral surface, and 

 pull it gently over the head with a forceps. 



4. The various viscera may now be fairly 

 easily displayed. Observe — 



(a) The very complicated diverticula contain- 

 ing blood (d). 



(b) The alimentary canal similar in appear- 

 ance passing direct from the head to the anus (a, c). 



(c) The rectum. A terminal portion white in 

 appearance (rect). 



