140 



REPORT 108, U. S. DEPARTMEXT OF AGRICULTURE. 



the size of a pinhead to that of a pea. Within each of these abscesses a number of 

 the Demodex were crowded together. They did not appear to affect the health of 

 the animal. D. bovis Stiles was recorded from hides of cattle in the United States. 

 They formed swellings, about the size of a pea, on the skin. AVithin each there were 

 a great number of mites. The presence of these tubercles lessens the value of the 

 hide to a considerable degree. Herds could doubtless be cleaned by dipping in 

 ^^^if,^^^^ some liquid similar to the sheep and cattle dips now in use 



«(I^SS?& against other mites. Borrel (1909) considers that there is eA-idence 



that leprosy is transmitted by Demodex, but the evidence is at the 

 most only suggestive and not conclusive; he also suggests that in 

 some cases Demodex mav be the vector of cancer. 



mB$m 



m 



M 



Family OPILIOACARIDJE. 



This family has been made for certain peculiar mites recently 

 described by With as Opilioacarus. They have a body about twice 

 as long as broad, with large, prominent, simple, five-jointed palpi, 

 and long, slender legs. The front and hind legs are more than 

 twice the length of the body. The abdomen is segmented, and 

 bears four pairs of dorsal spiracles. The cephalothorax has two 

 sessile eyes on each side. The mandibles are stout, two-jointed, 

 and chelate. The two claws at the end of the tarsus are situated 

 upon a caroncle. With considers that they represent a distinct 

 suborder, the Notostigmata, but what relation they have to other 

 mites is as yet uncertain. Several species have been described 

 from Italy, Algeria, Arabia, and Argentina. Nothing is known of 

 their life history or habits, except that some occur under stones. 



UNCERTAIN ACARI. 



Mention should be made of those groups of animals more or less 

 closely related to mites, but whose relationships are not agreed 

 Fig. 2Q2.—Poroceph- upon by naturalists. By some they have been placed in Acarina, 

 aiussp. (Original.) ^^^ ^^^ ^^^^ reason would seem to be that they do not fit into 

 other groups. They have not been studied by acarologists nor usually consid- 

 ered by them as coming within their field of observation. The first, the Linguatu- 

 lidse, are wormlike creatures, usually found in the nasal cavities, lungs, or connecting 

 passages of flesh-eating ver- 

 tebrates, such as snakes, 

 crocodiles, and carnivorous 

 mammals. Their larvae are 

 found in various tissues o 

 the prey of these carnivor- 

 ous animals. The body is 

 more or less ringed; the an- 

 terior part separated from 

 the rest, and with a central 

 mouth, and two pairs of 

 hooks each side of it. The adults have no legs, but some larva? have two pairs of leg- 

 like processes. Some of them become 2 or 3 inches long. Shipley, who has revised 

 the group, recognized 20 species. There are two principal genera: Linguatula with a 

 flattened body, and Poroccphalus (fig. 292) with an elongate, cylindrical body. 



The second group, the Tardigrades (fig. 293), or "water bears," have much greater 

 resemblance to acari, but whether more affinity or not is a doubtful question. They 



FiQ. 293.— A tardigrade, 



