TICKS OF THE BELGIAN CONGO. 



341 



efforts on the part of the parasite. When the chelicerae and hypostome have penetrated 

 sufficiently and the digits have cut tne smaller blood vessels, the tick proceeds to suck 

 in blood by means of a powerful pumping organ, the pharynx, which is situated in 

 the capitulum. The blood, traversing the pharynx and oesophagus, enters the highly 

 distensible intestinal caeca and the tick proceeds to swell in size. The blood is 

 imbibed slowly at first, the maximum increase in the engorgement of the tick usually 

 taking place during the last twenty-four hours (in Ixodida?) before the parasite 

 abandons the host. 



DORSAL PSOCESS 



EXTERNAL AIJTICU:;-* 



-PORE. 

 -ABTICULATIOSJ 



PLEXOS TENDON.. 

 EXTENSOR TENDON r- 



Fig. 48. Haemaphy salts cinnaharina var. 



-punctata, (Canestrini and Fanzago, 1877), 9 : 



showing mechanism of chelicera (Xuttall, 



Cooper and Robinson, 1908). 



Owing to the structure of the tick's mouth-parts they are frequently injured when 

 the parasite is forcibly removed from its seat of attachment. Due care should therefore 

 be taken in removing a tick, a fine pair of forceps with which the mouth-parts are 

 grasped, will be found useful for the purpose. If the broken off mouth-parts are left 

 in the wound considerable irritation may be produced, over and above that which is 

 occasionally caused by the bite itself. 



The salivary secretion of ticks has been shown by Nuttall to contain an anti-coagulin, 

 and there is reason to suppose that it may at times exert a toxic action. 



Whilst feeding, this being especially observable in Argasidae (Ornithodorus moubaia 

 and to a lesser degree in Argas persicus), ticks may give off considerable quantities of 

 clear fluid from glands whose ducts emerge between the coxae of the first and second 

 pairs of legs. This secretion of the coxal glands likewise contains an anti-coagulin. 

 Ticks frequently void excreta whilst feeding. 



The function of the anticoagulin is obviously that of preventing the coagulation 

 of the blood and consequently promoting its flow. (See further under 0. mouhata, 

 biology p. 345.) 



There can be no question but that massive tick infestation may be fatal. Animals 

 have been known to die from " tick worry." 



