NO. 138-2. 



THE ACARTXA OR MITES— BANKS. 



29 



The niiindibles are slender, needle-like, and retractile, thus ditfering 

 greatly from those of Tr<>iiilndiwiK Jind forming the warrant for a 

 sei^arate famil3\ 



The legs are commonly quite slender, the hind pair sometimes more 

 tiian twice as long as the body. They are seven-jointed and terminate 

 in two small claws. The last joint, or tarsus, 

 is nearly always shorter than the preceding 

 joint, and in the iirst and fourth pairs often 

 swollen. The ))ody and legs are densely cov- 

 ered with bristles or hairs, sometimes l)oth. 

 The hinder pair of legs are always quite re- 

 mote from the anterior pairs. The genital 

 opening is between the hind coxa^; the anal 

 opening is usually close behind it. 



The\' are usually found on the ground, 

 sometimes in ver}' hot situations, and run over 

 the surface or on low plants with great ra- 

 pidity. Other species occur in moss or under 

 fallen leaves in woods, 

 and one is al>undant 

 among the rocks near 

 the top of Mount 

 Washington. Several 

 species appear to live 

 in colonies, but most 

 are solitarj' in habit. 

 The eggs are deposited 

 on the ground or un- 

 der stones, often in clusters. The larva is a 

 six-legged mite attached to insects. When full 

 fed they drop to the ground and become qui- 

 escent, and after a varying time transform to 

 the adult. 



There are several genera in the family, but 

 only three are so far known from the United 

 States. In Smaris the mouth-parts are retrac- 

 tile, and so are often invisible; the palpi are 

 four-jointed and there is commonly an extra 

 pair of eyes near the anterior margin, making 

 six in all. In ASmaridia the mouth-parts are less retractile than in 

 Smaris^ and there are l)ut four eyes. The palpi are live-jointed and 

 the dorsal groove is sometimes swollen in the middle. 



Thor, who has recently published on this and allied families, makes 

 Smaris the type of a special family. He finds that in this genus there 

 are no spiracles near the beak, as in other Prostigmata, and that there 

 are no laro-e tracheal trunks in the bodv. There are a great many fine 



Fig. 39.— Rhyncholophus. a, 

 TALPi's; h, mandibles; e, beak; 



d, TRACHEAL pores; C, DORSAL 

 groove; /, TARSI'S. 



I.— Rhyscholophis 



MACULATUS. 



