118 Annals Entomological Society of America [Vol. X, 



nemid mites were included with the beetle mites in a suborder 

 called Heterotracheata. The beetle mites were divided into two 

 sections under this suborder, Ginglymosoma and Scleroderma. 

 The former section included the family HoplodermidcE and the 

 latter the families HypochthojiidcB, NothridcE, and Oribatidce. 

 Berlese has in the last few years described some interesting 

 new species, which show both the characters of the family 

 Hoplodermidoi and also those of the families Hypochthonidce 

 and OribatidcB. These should, I believe, be regarded as the 

 direct descendents of the "connecting links" between these 

 families, and their discovery must necessarily cause us to regard 

 the Hoplodermidce as being more closely bound to the other 

 families than was formerly believed. 



Considering the beetle mites as a phylogenetic unit, dis- 

 regarding for the present their place in the order to which 

 they belong, we find that they can be easily divided into four 

 families already recognized by others. These four families 

 I have divided into fourteen subfamilies, which are given with 

 the families in the following key: 



A KEY TO THE FAMILIES AND SUBFAMILIES OF THE BEETLE MITES. 



A. Cephalothorax immovably united to abdomen; tracheae usually present. 



B. Abdomen without dorsal grooves or sutures dividing it into parts; integu- 

 ment well chitinized. 

 C. Abdomen provided with chitinous, wing-like expansions known as ptero- 

 morphse, which usually are large and conspicuous, but which may be 



small and shelf-like Oribatidae 



D. Chelicerse swollen at their bases, styliform beyond, and ending in 



minute chelae Pelopin^ 



DD. Chelicerce stout in the middle and with large chelae. .. .Oribatin^ 

 CC. Abdomen without wing-like expansions known as pteromorphfe, even of 



the rudimentary, shelf-like type Nothridae 



D. Chelicerse rod-like, serrate toward their tips Serrariin^e 



DD. Chelicerae not rod-like, chelate. 



E. Fourth pair of legs fitted for jumping Zetorchestin^e 



EE. Fourth pair of legs not fitted for jumping. 



F. Lamellae present, being either blade-like or in the form of straight 

 chitinous ridges. 

 G. Integument of dorsal surface of abdomen smooth, and without 



markings of any kind Notaspidin^e 



GG. Integument with markings in the form of reticulations, tubercles, 



pits, sculpturings, or ridges Tegeocranin^ 



FF. True lamellae absent, but crooked or irregular ridges may be 

 present. 

 G. Some of the segments of the legs other than the femora swollen 

 toward their distal ends and pedicellate proximally; legs 



slender Damaein^ 



GG. None of the segments of the legs swollen and pedicellate except 

 the femora. 

 H. Ventral plate present, and usually containing the genital and 



anal apertures Nothrin/E 



HH. Ventral plate absent or rudimentary, and in no case inclosing 

 genital and anal apertures Lohmannin^e 



