TICKS. 227 



mouth parts. It is the intermediate host of Sp. duttoni. (South African 

 tick fever.) 



Subfamily Ixodinae. Mouth parts project in front of body when 

 viewed dorsally. Scutum present. Stigmal plates posterior to fourth 

 pair of legs. Adults have suckers on claws. 



Section Ixodce. Transverse recurved preanal groove in female. 

 Genus Ixodes. 



Section Rhipicephalus . No preanal, but postanal groove in female. 



In the genera Aponomma and Hvalomma the palpi are long and 

 slender. The genus Aponomma has eyes. Amblyomma has no eyes. 



Palpi are short in the genera Haemaphysalis, Dermacentor and 

 Margaropus. 



Haemaphysalis has no eyes; Dermacentor and Margaropus have 

 eyes. In Dermacentor the head is transversely oblong; in Margaropus 

 it is hexagonal. Dermacentor andersonii transmits spotted fever of 

 the Rocky Mountains. 



LlNGUATULIDA. 



These are vermiform acarines more or less distinctly annulated. 

 They have hooks at either side of the mouth. 



Linguatula rhinaria. This has been observed in man both in 

 larval and adult stages. The female lays eggs which, gaining freedom 

 through the nasal mucus, are swallowed by various animals. A larva 

 develops which bores its way through the gut and encysts in the liver 

 or mesenteric glands. After several moultings, they work their way 

 again to the intestines and so get out of the body of their host; or they 

 may wander to lungs and trachea and either escape or take up their 

 position in the nostrils and produce eggs. Consequently, one animal 

 may act as intermediate and definitive host or these cycles may take 

 place in distinct animal hosts. 



Porocephalus constrictus. The adult form lives in snakes and 

 the eggs are probably ingested by drinking water. These eggs de- 

 velop into a curled-up, ringed larva, which is encysted especially in the 

 liver or lungs. These escape and are swallowed by the snakes, their 

 definitive hosts. 



