12i COLEOPTERA OF NORTH AMERICA. 



Body contractile, legs broad. Acanthocerini. 



Body not contractile, legs normal. Nicagini. 



Epimera of niesothorax not attaining the rounded coxa?. Tkogihi. 



Tribe I.— COPRIjVI. 



These insects are of rounded form, and live almost exclusively 

 in excrements. The clypeus is expanded so as to cover entirely 

 the oral organs; the lobes of the maxilke are large, ciliated, and 

 of a membranous or coriaceous structure ; mandibles lamelliform, 

 principally membranous, with only the outer margin corneous ; the 

 mentum is emarginate; antennae 8- or 9-jointed, club 3-jointed; 

 epimera of metathorax covered ; mesosternum very short ; middle 

 coxae oblique, widely separated ; posterior tibia? with a single 

 terminal spur ; tarsi usually without the bisetose onychium ; ely- 

 tra subtruncate, leaving the pygidium exposed ; ventral segments 

 six, all connate. 



It is in this tribe alone that species occur in which the anterior 

 tarsi are wanting in the females, or in both sexes ; the claws of 

 the tarsi are also sometimes wanting. Organs of stridulation are 

 found on the dorsal surface of the abdomen of certain species. 



According to the form of the posterior tibia?, two sub-tribes 

 are indicated : — 



Middle and posterior tibia? slender, scarcely enlarged. Atecchini. 



Middle and posterior tibia? dilated at the extremity. Coprini. 



Sub-Tribe 1. — Ateucliilii. 



These species deposit their eggs in balls which they construct 

 of the materials on which they live, and roll these balls to a con- 

 siderable distance, a labor for which their long, slender, and 

 slightly curved posterior tibiae fit them. The head and thorax 

 never bear horns, and the sexes are alike in appearance, except 

 in Deltachilum gibbosum, where the elytra of the male are each 

 armed with a large dorsal tubercle. The anterior coxa? are 

 slightly prominent internally. The onychium between the claws 

 is wanting. 



Our genera are but two in number, and each represents a sepa- 

 rate group of this sub-tribe ; the groups of genuine Ateuchi and 

 Minthophili not occurring in our fauna. 



Epipleura? of the elytra narrow, or wanting ; anterior tarsi distinct. 



Group I. GYMNOPLEUTJ. 



