62 



PROCEEDINGS OF THE NATIONAL MUSEUM, 



VOL. XXVIII. 



The UropoclicUw are divisible into comparatively few genera. In 

 general appearane(^ the}" are quite dift'erent from most of the Gan^-asidte, 



being shorter and their legs more or less 

 hidden under the body. They are familiar 

 to most entomologists when attached to 

 beetles and other insects. Besides the char- 

 acters given in the table for the separation 

 of these forms from the Gamasidfe, it may 

 1)0 added that the mandibles are very long 

 and slender, ending in delicate chehe. In 

 fact the mandibles in some 

 species are twice the length 

 of the liody, and when re- 

 tracted the bend near the 

 middle is near the posterior 

 walls of the body. Most of 

 the Uropodida* that are 

 found on insects are there 

 for the Y)urpose of transportation and not as para- 

 sites, l)ut in certain forms found on ants the mite is a 

 true parasite. The species that use the insect as an aid 



to mip-ration 



Fic. 114. — Uropoda; caronclk 



AND PERITREME. 



115.— Uropoda 



p. PEDICEL. 



are attached 

 thereto ])y a 



pedicel of excrement; those 

 that are true parasites are not 

 so attached. Most of those 

 that are attached by this anal 

 pedicel are not adults, but in a 

 nymphal stage, and are called 

 "^ /i//mp/i(f jtedimculatar The 

 mite can detach itself by a 

 fresh excretion. They occur 

 on insects that breed in places 

 suitable for the mites. There- 

 fore the mites are sure to ])e carried to a spot where they can drop off 

 and find the desired breeding grounds — decayed wood, humus, manure, 

 or fallen leaves. Sometimes the insect is so completely covered b}^ 

 the mites that it can not be seen. 



The genera may be tabulated as follows: 



1. Venter lirovided with impressed fove;e for tlie reception of the leors 2 



No such fove;e 4 



2. Body irregular, dorsum sculi)tured Glypftopsis 



Body regular in form; dorsum evenly convex; no scul])ture, except punctuation. 3 



'^. Leg I ])rovided with claws Vrojioda 



Leg I without claws <■ Cilliba 



Fig. 116. — Uropoda .sp., fro.m below. 



