144 COLEOPTEItA OF NORTH AMERICA. 



tirely destitute of tubercles, and by the clypeus being flat, para- 

 bolic and finely margined ; the mandibles project but slightly, 

 and are not toothed externally. 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; antennas 10-jointed (9-jointed only in certain species 

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

 base ; the prosteimuni is prominent behind the coxas ; the tarsi 

 are cylindrical. 



Our two genera have the mesosternum scarcely visible between 

 the middle coxas ; 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. 



Sub-Tribe 2.— ©ryctini. 



The insects of this sub-tribe vary much in size and form, but 

 have the following characters in common : — 



Labial palpi inserted at the sides of the mentum; mandibles 

 prominent, usually toothed externally ; head more or less tuber- 

 culate (except in Strategus), always with some elevations, some- 

 times armed with a horn ; thorax usually tuberculate or horned ; 

 anterior feet not elongate in the males; clypeus not parabolic, 

 but rather triangular, reflexed with one or two small apical teeth ; 

 mentum narrowed in front ; posterior tibiaB expanded at the ex- 

 tremity (except in Polymcechus), sometimes digitate; first joint 

 of hind tarsi more or less elevated at its upper extremity. Stridu- 

 lating organs are found except in Aphonus and Polymcechus. 



The sexual characters are usually in the greater development 

 of horns or tubercles in the male, rarely {Ligyrus relictus) in 

 the thickening of the outer claw of the anterior tarsi ; and, in 

 Polymcechus, in the elongation of the antennal club, and the outer 

 claws of the middle and hind tarsi being armed with a strong 

 tooth. 



Three groups are represented : — 



Posterior tibiae expanded (sometimes but slightly) at the extremity, trun- 

 cate, and ciliate ; 

 Antennce alike in both sexes. Pentodoktes. 



