SCARAB^IDAE. 259 



Sub-Tribe 2.— Oryctini. 



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

 have the following ciiaracters in common: — 



Labial palpi inserted at the sides of thementuin; 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; clypcus not parabolic, 

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

 mentuni narrowed iu front; posterior tibiai expanded at the ex- 

 tremity, sometimes digitate ; first joint of hind tarsi more or less 

 elevated at its upper extremity. Stridulating organs are found 

 except in Aphonus. 



. The sexual characters are usually in the greater development 

 of horns or tubercles in the male, rarely (Ligi/rus relictus) in 

 the thickening of the outer claw of the anterior tarsi. 



Two groups are represented : — 



Posterior tibiae expanded (sometimes but slightly) at \hi'. extremity, trun- 

 cate, and ciliate. Pe.ntodontes. 

 Posterior tibiae digitate or festooned at the extremity. Okyctes. 



Group I. — Pentodontes. 



Moderate-sized, robust, convex species, having the head slightly 

 tuberculate, or rather, iu our species, with small anterior ridges 

 or teeth, alike in both sexes; thorax sometimes with a small acute 

 tubercle near the anterior margin, sometimes entirely uniform, 

 convex. 



Three genera occur in our fauna: Ligyrus, generally diffused; 

 Aphonus, from the Atlantic and Central districts. 

 Front tibise digitate ; 



Stridulating organs on tlie inner surface of tlu- <'Iyt(a : mandibles toothed 

 ext.irnally. Ligyrus. 



Stridulating organs entirely wanting; mandibles not t<Kithed. 



Aphonus. 

 Front tibiae without teeth, rounded at tip. Orizabus. 



The last genus is founded upon a Mexican species which 

 extends into New Mexico. It greatly resembles in appearance 

 Aphonus clunalis. 



