LINGUATULIDA 289 



surface of male without adanal plates in Dermacentor, Haemaphysalis, Aponomma 

 and Amblyomma, but with one or two pairs in Hyalomma, Rhipicephalus and 

 Margaropus. 



In the genera Hyalomma, Aponomma and Amblyomma the palpi are long and 

 slender and of about uniform width of segments. 



In Hyalomma the segments of palpi are of about equal length. In Aponomma 

 and Amblyomma the second palpal segment is much longer than the others. Ambly- 

 omma differs from Aponomma in being very ornate and in having eyes. 



In the genera Haemaphysalis, Dermacentor, Rhipicephalus, and Margaropus 

 the palpi are short. 



Haemaphysalis has very broad rostrum, triangular palpi, and no eyes. Derma- 

 centor has a square rostrum with short thick palpi, the second and third joints being 

 as broad as long. Dermacentor andersoni transmits spotted fever of the Rocky 

 Mountains not D. reticulatus. 



Rhipicephalus has palpi without transverse ridges and comma-shaped stigmal 

 plates. The stigmal plates of Margaropus are nearly circular and the palpi have 

 acute transverse ridges externally. Margaropus annulatus transmits Texas fever 

 of cattle. This tick is also called Boophilus bovis or B. annulatus. Some authors 

 term it Rhipicephalus annulatus. Larvae developing from eggs of female ticks 

 which have fed on cattle infected with Texas fever transmit the disease which is due 

 to a protozoon Babesia bigemina. 



LINGUATULIDA (TONGUE WORMS). 



These are vermiform acarines more or less distinctly annulated. They have 

 retractile hooks at either side of the elliptical mouth. 



If the hooks are to be considered not as degenerated legs but antennae and palpi, 

 then there is no vestige of legs in the adult. The sexes are separate. 



Linguatula rhinaria. This has been observed in man both in larval and adult 

 stages. 



The male is white and about 3/4 inch long while the female is about 4 inches 

 long, tadpole shape, yellowish in color, and has about ninety segments, lives in "the 

 nasal cavity and frontal sinus of dogs, rarely in horses and sheep, and very rarely 

 in man. 



The female lays embryo-containing 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 to become adults and produce eggs. Consequently, 

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

 place in distinct animal hosts. 



The larval form (1/5 in.) is far more common in man than the adult. Symptoms 

 are referred to liver in both larval and adult stage, and epistaxis and nasal symptoms 

 for adult stage only. 



Porocephalus constrictus. The adult form P. moniliformis lives in the lungs of 

 snakes and the eggs are probably ingested by drinking water. These eggs develop 



