108 



Acarology 



UROPODINA KRAMER, 1881 



The Uropodina are characterized (except for the intermediate group 

 of genera in the family DiscoureUidae) by the arrangement of the 

 gnathosoma. The anterior ventral portion of the body is excavated so 

 that the gnathosoma and tritosternum are enclosed in a cavity, the 

 dorsal wall of which is formed by the body wall while coxae i can 

 close it ventrally. This cavity is frequently called a camerostome. The 

 metasternal plates of this group are also either greatly reduced {JJro- 

 diaspis and Uroplitella) or completely absent. The male genital open- 

 ing is in the center of the sternal plate, as is the epigynial plate. The 

 tritosternum is frequently divided into three lacinae anteriorly. The 

 dorsal plate is usually entire in the adults. Depressions for the legs are 

 found on the ventral surface so that the short legs may be folded com- 

 pactly against the body. The stigmata are opposite leg ii or in. The 

 peritremes are usually convoluted to conform to the ridges that limit 

 the depressions into which the legs can be folded. The chelicerae 

 usually extend for some distance into the idiosoma and in some cases 

 may almost reach the posterior end. 



Twelve families are placed in this group with assurance. Two other 

 families that are questionable are included here. The Trematuridae 

 Berlese, 1917 was supposedly characterized by the presence of four 

 stigmata. Tragardh 1942 has shown Berlese to be in error as regards 

 the number of stigmata, but Tragardh was unable to clarify the system- 

 atic position of Trematura patavina (Canestrini), 1885 with the aid 

 of Berlese's specimens. The family DiscoureUidae lacks the camero- 

 stome and is thus intermediate between the Uropodina and the Trachy- 

 tina. A key to the families modified from Tragardh 1944 follows. 



Figure 80 The arrangement of the dorsal 

 plates of representative genera of the 

 Uropodina, Top row, from left to right, 

 Phaiilodiaspis, Urodiaspis, Oodinychiis; mid- 

 dle row, Phaidodinychits, Trematiirella, Pliyl- 

 lodinychiis; and bottom row, Eiitrachytes, 

 Cilliba, Urodinychus. (After Tragardh 1944 

 and Vitzthum 1935) 



