144 COLEOPTERA OP NORTH AMERICA. 



Elytra truncate behind, leaving two segments of tlie ab- 

 domen uncovered. 



Abdomen with five free ventral segments, the first very 

 large, the fifth very short, closely applied to the last d<jrsal 

 segment, which is triangular and defiexed. 



Anterior coxas transverse and not prominent in the first 

 sub-family, globose in the second ; middle and posterior coxae 

 widely separated, not prominent, rounded, or rather sub- 

 quadrate, the latter not extending to the sides of the body. 



Legs short, retractile ; tibite compressed, anterior ones 

 usually toothed, posterior sometimes toothed; spurs distinct, 

 those of the anterior pair very unequal. Tarsi slender, short, 

 5-jointed (except in Acritus, Aeletes, where the posterior 

 ones are 4-jointed); claws (in all of our genera) two, simple; 

 anterior tarsi usually received in grooves on the anterior face 

 of the tibiee. 



A very well defined family of insects, moderately numerous, 

 nearly all of a shining black color, with tlie elytra variously 

 .sculptured with striag ; some few species of Hister and Saprinus 

 liave the elytra marked with red, and a few of the latter genus 

 are metallic in color. The form of body is variable ; those of the 

 first tribe are oblong and flat, with prominent mandibles; the 

 others are round, oblong, oval, globose, or cydindrical, some 

 depressed and some convex. The species live under bark of 

 trees, in excrements, and in carcasses. When touched, the 

 insects retract the antennae and feet, appearing as if dead. 



The metasternum is marked by two distant lines diverging pos- 

 teriorly, and the first segment of the abdomen with two similar 

 ones, recalling somewhat the sculpture of the same parts in Coc- 

 cinellidfe. 



The genera in this family appear to us to have been multiplied 

 unnecessarily by later authors. We accordingly have made, when 

 necessary, two tables, one of the genera as understood in the 

 great monograph of Marseul, the other of those which appear to 

 us to be entitled to real generic distinction. 



This family may be divided, following the example of Lacor- 

 daire, into two very natural tribes, according to tlie position of 

 the liead in repose: — 



Head porrected. Hololeptini. 



Head retracted, bent downwards. Histrini. 



