g 



45 



Not being well armed for aggressive warfare, this group is 

 very remarkable in its adaptation for defense. The thick chi- 

 tinous integument of the group when taken into consideration 

 with the special structures of the Oribatidce, the pteromorphge 

 or abdominal wings, affords an excellent protection against some 

 of their smallest, though most troublesome, enemies. When the 

 least disturbed, most of the species with these chitinous ab- 

 dominal wings will fold the legs up underneath the body and 

 close down the abdominal wings over them, so that they are 

 almost or quite completely concealed and protected. In case 

 of the Hoplodermidce, which have the cephalothorax hinged to 

 the abdomen, they at once feign death upon being disturbed, 

 fold themselves into a small ball by bending the cephalothorax 

 down over the ventral surface of the abdomen, at the same 

 time drawing up the legs, and are thus completely covered by 

 the cephalothorax. 



In their movements the Oribatoidea are sluggish as com- 

 pared with the other Acarina. As a rule the smooth, shiny 

 species are more active than the larger, rough species. The 

 species of the genera Neoliodes and Nothrus are especially slow 

 in their movements. One species, Zetorchestes micronychus, 

 which though common in Europe has been found in only one 

 place in America, is quite unique in being the only oribatid 

 which is saltatorial. 



Many of the Oribatoidea pass the winter in moss. Some 

 of the species which live upon the leaves of trees, apparently 

 winter under the bark. 



The Taxonomy of the Higher Groups of the Oribatoidea. 



Michael, the expert acarologist already mentioned, regards 

 the group of beetle-mites as a family, and in his monograph 

 of them in " Das Tierreich" (Lief. 3, 1898) divided the group 

 into seven subfamilies. I can hardly agree with this author in 

 all respects as to this division, for although the characters 

 which separate some of his subfamilies are fundamental and are 

 correlated with differences in habit as well as structure, others 

 are somewhat variable and hardly of more than generic im- 



