NEW AMERICAN ACARINA. 



TRANS ACTTIONS 



OF THE 



AMERICAN ENTOMOLOGICAL SOCIETY. 



voIvUnie: XXII. 



ON THE ORIBATOIDEA OF THE UNITED STATES. 



BY NATHAN BANKS. 



The Oribatid mites are easily recognized by the division of the 

 body into two regions, cephalothorax and abdomen, by the jDresence 

 of a seta to a small pore near each posterior corner of the cepha- 

 lothorax, by having the legs in the normal position (not separated 

 in pairs), and by their coriaceous tegument. Because of this latter 

 character they have often been called " beetle-mites." The body of 

 an Oritabid is readily divided into two parts, the smaller and anterior 

 portion is the cephalothorax, the posterior part is the abdomen ; 

 beneath the tip of the cephalothorax is a distinct, articulated por- 

 tion, the true head. To the head is attached the mandibles and 

 palpi, both of minute proportions. The cephalothorax is usually 

 more or less triangular ; a plate of tegument frequently extends from 

 the base of the abdomen down upon the cephalothorax, thus making 

 the surface of the cephalothorax continuous with that of the abdo- 

 men, and the dorsal outline entire. This plate is known as the tectal 

 plate or tectum. Whenever there is a distinct break in the dorsal 

 outline of the body at the junction of the cephalothorax and abdo- 

 men the tectal plate is considered to be absent. And on this char- 

 acter the true Oribatidfie is divided into two sub-families, the Nothrinse 

 in which it is absent, and Oribatinie in which it is present. Most of 

 the genera of the former have but one claw to tarsus, and most of 

 the genera of the latter have three claws ; but there are prominent 

 exceptions in each group. In some forms the tectal plate is free at 



TRANS. AM. ENT. SOC. XXII. (1) JANUARY, 1895. 



