258 COLEOPTERA OP NORTH AMERICA. 



rarely truncate. The claws of the tarsi are equal, and simple, 

 except in the male of Ligyrus t^elicius, where the inner claw of 

 the anterior tarsi is thickened, dilated, and suddenly incurved. 

 The labruni, always visible in the preceding tribe, is here almost 

 invisible, and sometimes in part membranous. 



This tribe, among its foreign members, numbers the largest 

 Coleoptera existing; some of the genera are remarkable for the 

 size a.nd form of horns on the thorax and head of the males. 



Organs of stridulation are found in many genera; they consist 

 of rugose spaces, usually on the propygidium, sometimes on the 

 inner surface of the elytra. The fifth ventral segment and the 

 propygidium are connate, and the spiracle is on the suture nearer 

 the anterior than the posterior margin. 



The sub-tribes represented in our fauna are as follows: — 



Labial palpi inserted at the sides of the nientum ; « 



Head and prothorax unarmed in both sexes. Cyclocephalini. 



Head and prothorax armed, or at least tuberculate, in both sexes ; 



Anterior feet of the males not elongated. Okyctini. 



Anterior feet of the males elongated. Dynastini. 



Labial palpi inserted behind the mentum. Phileurini. 



Sub-Tribe 1. — Cyclocephalini. 



But two genera of this sub-tribe exist in our fauna; they have 

 the appearance of Melolonthinae, and are readily distinguished 

 from the following sub-tribes by the thorax and head being 

 entirely destitute of tubercles, and by the clypeus being flat, 

 parabolic, and finely margined ; the mandibles project but slightly, 

 and are not toothed extet-nally. The males have the fifth joint of 

 the anterior tarsi much enlarged, and the club of the antennae is 

 sometimes longer than in the female. Stridulating organs none; 

 posterior tibiae not festooned nor expanded at tip; mentum trun- 

 cate in front; antennre 10-jointed (9-jointed otdy in certain species 

 of Cyclocephala) ; the thorax is only partially margined at the 

 base ; the prosternum is prominent behind the coxjb ; the tarsi 

 are cylindrical. 



Our two genera have the mcsosternum scarcely visible between 

 the middle coxaj; Cyclocephala has the mandibles narrow, scarcely 

 curved; Chalepus has them broad, rounded externally, and curved. 



Cyclocephala is generally diffused ; Chalepus has not yet been 

 found on the Pacific slope. 



