THE ACAEINA OK MITES. 



87 



female deposits one large egg at a time. In the male the lower claw of the chela, or 

 mandibles, is provided with a brush of long hairs, which is considered to assist in trans- 

 ferring the sperm at mating. Most of the species are hairy all over the dorsum, others 

 only around the margin. They occur in Europe, Africa, Australia, and South America, 

 and three are known from the United States. 



A number of genera have been made, but most of these are scarcely more than sub- 

 genera and based largely on the females. They are distinguished as below: 



1. But one genital shield Parantennulus. 



With three genital shields 2 



2. Shields near vulva partly cover it, the anal united to the ventral ...Physalozercon. 

 Shields near vulva do not cover it 3 



3. The ventro-anal shield elongate, not occupying the available sipace. Antennophorus. 

 The ventro-anal shield very broad, occupying all available space 4 



4. The shield near Aailva united to the ventro-anal shield . Neomegistus, Echinomegisius . 

 The shield near vulva separate from ventro-anal shield 5 



5. Metasternum divided Paramegistus. 



Metasternum entire Antennomegistus. 



A closely related genus, Ophiomegis- 

 tus, occurs under the scales of certain 

 snakes in the Philippines. They are so 



flat that they can not be noticed under Kh>\y^^^^^^\^ ''•^ ) ■ - 



the scales, but leave the snake when the "n^v" U ^ ^ ] J 



latter is placed in alcohol. P^fW^ ^ ^ ^ "^ ^ \-\ 



In Ptocharus, an Australian form oc- ^)7/rr /* ^ ^ \ \^ '^ '^'^V 



curring on ants, the abdomen may juf I ^^^'^ / . ' ."^ ^ •>' 



become greatly distended with food, y4[ ^ ^ ^ "" ( -) ^ '^"^0^^ 



becoming nearly as high as broad. ■^/y^^ / ( r ^ ) )*^ "^ -^ '^'^ 



In general appearance the Uropodinse ^f ^^^^^ ^ ^r ^ l"* ^ "^ ) 



(fig. 172) are quite different from most '« ^'^^^^bCC K^ 



oftheParasitinse, being shorter and their ^ .„ . ^ ., . . 



, . '.., ^ T - ^ , Fig. 170.— AntennopJiorus uhlmanni. (After 



legs more or less mdden under the body. Haller.) 



They are familiar to most entomologists 



when attached to beetles and other insects. Besides the character given in the table 

 for the separation of these forms from the Parasitinae, it may be added that the mandi- 

 bles are very long and slender, ending in delicate chelae. In fact, the mandibles in 



some species are twice the length 

 of the body and when retracted 

 ^\t^"-- "£fe. /\ ^^^ bend near the middle almost 



reaches the posterior walls of the 

 body. Most of the Uropodinae 

 __ th a t are found on insects are there 

 Fig. 171. -Ant carrying three Antennophori. (After Janet.) ^o^" tl^^ piu-pose of transportation 



and not as parasites, but in cer- 

 tain forms found on ants the mite is a true parasite. The species that use the insect 

 as an aid to migration are attached thereto by a pedicel of matter secreted by glands 

 near the anus; those that are true parasites are not so attached. Most of those that 

 are attached by tliis anal pedicel are not adults, but in a nymphal stage and are 

 called "nympha pedunculata." The mite can detach itself by a fresh secretion. 

 They occur on insects that breed in places suitable for the mites. Therefore the mites 

 are sure to be 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 by the mites that it can not be seen. They have been found 

 attached to wood lice (Porcellio) and to caterpillars. Cummins has shown that 

 Uropoda feeds on bacteria and minute fungi that grow on the substances inhabited 

 by the mite. He made many experiments with them. On placing the bacterial 

 matter on a slice of potato near the mites they would, through some sense, at once 



