56 



REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. 



ScaptognathiLS (fig. 101) and Simognathus (fig. 102) have each a number of species, 

 neither with much resemblance to the true Halacaridse. Lejptognathus is similar to 

 Halacarus, but the palpi are situated close together at the apex of a prominent beak, 

 and the last joint of the palpus is not so slender. The species occur not far from shore. 

 Acaromantis is similar to Simognathus, but the first pair of legs is destitute of claws, the 



very short tarsus ending in a number of hairs. 

 Atelopsalis is based on an abyssal species similar to 

 ScaptognathiLS, but the rostrum is small and short. 



Of Agaiie about a dozen species are known. Most 

 of them occur not far from shore. They have the 

 first pair of legs much thicker than the second pair. 

 Rhomhognathus also includes about a dozen species, 

 most of which occur on algae in the littoral region, but 

 one was described from fresh water in England. 

 They are much smaller than the ordinary Halacarus, 

 usually only a third of a millimeter long. 



Superfamily IXODOIDEA. 



The members of this group, commonly known as 

 ticks, are of all acarians the most familiar to most 

 people. They are all mites of considerable size; even 

 (Origi- the young or "seed ticks" are visible to the naked 

 eye, while a full-grown engorged female maybe more 

 than one-half inch long. Their abundance on many of the domestic animals and 

 occasional occurrence on man have rendered them well-known objects of disgust in 

 every clime. 



Fig. 102.— Simognathus sp. 

 nal.) 



Tig. lOZ.—Argas miniatns, from below. 

 (Author's illustration.) 



YioAOA.—Otdbius mcgnini: Nymphal form and details, 

 (From Marx). 



Tlic body is covered by a tough, leathery skin, which in the female becomes greatly 

 distended as she engorges herself with the blood of the host. Before distention the 

 tick is of a somewhat triangular outline, flat, \\'ith prominent, slender legs, and a 

 beaklike rostrum in front. When the female becomes swollen these structures may 

 be hardly noticeable, and the whole creature looks like some large seed or beau. In 



