490 AN INTRODUCTOIN TO ENTOMOLOGY 



beetles in the shortness of the wing-covers and in having the dorsal 

 part of the abdominal segments entirely homy; but they differ 

 from them in that the abdomen is not flexible, and in having fewer 

 abdominal segments, there being onh' five or six on the ventral side. 

 The species are chcstnut-bro^^^l, dull yellow, or piceous, and are 

 usualh' slightly pubescent. The antenna) are usually eleven-jointed, 

 rarely ten-jointed. The elytra and abdomen are convex and usually 

 wider than the head and prothorax. These beetles are usually found 

 under stones and bark, or flying in the twilight; a few species have 

 been foimd in the nests of ants. There are three hundred and fifty- 

 five described North American species. 



The family CLAVIGERID^, or the ant-loving beetles, includes 

 a small number of beetles that resemble the Pselaphida2 in the char- 

 acters given above except that the antemiee are only two-jointed. 

 These beetles live in the nests of ants. They excrete from small 

 tufts of hairs, on the three basal abdominal segments, a fluid of 

 which the ants are very fond. The ants caress the tufts of hairs with 

 their antennse, causing the exudation of the fluid, which they greedily 

 swallow. The ants are said to feed the beetles and to allow them to 

 ride about on their backs, when the beetles wish to do so. Only 

 seven North American species are described. 



The family TRICHOPTERYGID^, or the feather-wing beetles, 

 includes the smallest beetles that are known; most of our species are 

 less than i mm. in length. The most striking feature of the typical 

 forms is the shape of the wings, which are long, narrow, and fringed 

 with long hairs, being feather-like in appearance; but in some species 

 the wings are wanting. Some species live in rotten wood, muck, 

 manure, and other decaying organic matter; few have been found in 

 ants' nests. There are about eighty described species in ova fauna. 



The family SCAPHIDIIDvE, or shining fmigus-beetles, includes 

 small, oval, very shining beetles, foimd in fungi, rotten wood, dead 

 leaves, and beneath the bark of logs. The elytra are broadly truncate 

 behind, not covering the tip of the conical abdomen. But little is 

 known regarding their life-history. There are fifty described North 

 American species. 



The family SPH^RITID^ is represented in our fauna by a 

 single species, Sphcsrites glahrdtus, which has been found in Alaska and 

 California. This beetle is very similar in appearance to those of the 

 genus Hister. For distinguishing characters, see table, page 470. 



The family SPHvERIID^ includes a single genus, Sphcerius, 

 which is represented in North America by only three known species. 

 They are very minute beetles, measuring about .5 mm. in length; 

 they are very convex, and may be found walking on mud or under 

 stones near water. 



The family HISTERID.^ includes certain easily recognized 

 beetles which are found about carrion and other decomposing sub- 

 stances. They are mostly small, short, rounded or somewhat square- 

 shaped beetles, of a shining black color, with the wing covers marked 



