THE ACAEINA OR MITES. 



89 



plate, and Uropoda, in vrhich the anal plate is wholly united to the ventral A\ithout 

 trace of a suture. 



Species of Uropoda are frequently found attached to various beetles. One of these 

 is common on the Colorado potato beetle, and it was formerly supposed by many 

 economic entomologists that the mites fed upon the beetle. It has lately been showTi 

 that some species feed on bacteria and small fungi. The species are very numerous; 



Tig 



174. — Uropoda 

 sp.; p, Pedicel. 

 (Author's illustra- 

 tion.) 



Fig. 175. 



Uropoda sp., from below. (Author's 

 illustration.) 



some are smooth, others hairy; nearly all of a red-brown fawn color. The species of 

 Glyphopsis have also been found in ants' nests, and seem to live on good terms with the 

 ants, although their exact status is not known. One species, G. michaeli Ewing, is 

 recorded from Illinois. It differs very Uttle from Trachyuropoda. TJroseius and Poly- 

 aspis are based on a few forms, and not well known; a species of the latter genus has 

 been found on Orthosoma in Ohio. 



Trachytes contains two or three p>Tiform species 

 found in moss. The genus was formerly called Celaeno. 

 Cilliba is similar in appearance to Uropoda. Some 

 species have been found in moss, but others occur 

 parasitically upon ants, attached to the thorax or 

 abdomen. One of our species, C. circularis Banks, 

 has been found thus fastened to the thorax of Cre- 

 mastogaster lineolata. Another species, C. hirsuta 

 Banks (fig. 176), was taken upon a species of Lasius 

 in Arizona. 



The relation existing between the Cilliba and the 

 ant has formed the subject of several recent investi- 

 gations, both by Wasmann and by Janet. The mites 

 which cling to the abdomen of the ant do not seem to 

 be disturbed by the ant, but if a mite was placed on 



the ground of the nest it was seized and destroyed by the ants. The mites bite 

 through the soft skin situated between the segments, and thus draw blood from theii- 

 hosts. 



The genus Dinychus (fig. 177) is peculiar in having enormously long extensile 

 flexible mandibles. The mandibles are more than twice as long as the entire animal, 

 and can be retracted so that the bend in them is close against the posterior walls of 

 the abdomen. The tips of these mandibles are distinctly chelate. We have one 

 species in this country. 



From New Guinea, Canestrini has described several species of a remarkable genus — 

 Deraiophorus. They have a paii- of plate-like projections over the head, and from these 



Fig. ITd.— Cilliba hirsuta from 

 below. (Author's illustration.) 



