second pair, there is a pore, from which the secretion 

 of the large coxal gland, described later, is at times 

 exuded. 



(2) Argas. Note the pit-like structures on the 

 dorsum and also the absence of the fold around the 

 base of the rostrum. 



INTERNAL ANATOMY AND DISSECTION OF TICKS 

 (A) ORNITHODOROS 



1. With a sharp pair of scissors snip all round the 

 edge so that the dorsal and ventral surfaces of the tick 

 are completely separated. 



2. Place the tick in a dissecting trough* in salt 

 solution, and fix the ventral chitin by means of fine 

 pins or hedgehog quills. Remove the dorsal piece by 

 grasping it behind with a pair of forceps and dragging 

 it forwards over the head, detaching any structures 

 which may adhere to it with a touch or two of a needle. 



3. Whilst carefully removing tracheal tissue and 

 separating the organs observe, in the female, a thin 

 sheet of tissue stretched over the whole dorsum. This 

 is composed of fat tissue and tracheal branches. 



Heart. In the central line is the tubular heart 

 dilated, at about the junction of the posterior with the 

 middle third of the body to form a conspicuous sac. 



Alimentary Diverticula. Note that there is a 

 central short median ventricle or sac receiving anteriorly 

 the oesophagus and ending posteriorly in the fine, almost 

 capillary, tube which passes to the rectum. Trace out 

 a number of anterior, lateral and posterior blind 



* A dissecting trough -^an be purchased, or readily made in the following way. 

 Put some pieces of lead at the bottom of a convenient dish and pour over them a 

 mixture of melted paraffin wax (melting point about 60 C.) and soot or fine animal 

 charcoal. 



