THE CANADIAN ENTOMOLOGIST. 73 



Of the above-mentioned tribes the Hydroporini contains nearly all of 

 the small species, and can be treated only with considerable difficulty, 

 as the genera are distinguished by structural characters not always evident 

 without the destruction of a specimen. After some practice, however, 

 the facies will be found a tolerably reliable guide. The genera may be 

 known by these characters : 

 A. Small (.06 to .07 in). First ventral connate with hind coxee. 



Form rounded, robust . . Desmopachria. 



Form oblong, depressed Bidessus. 



AA. Larger (usually over .10 in.) First ventral free. 



b. Scutel distinct Celitia. 



bb. Scutel invisible. 



Elytral ligula* distinct, abrupt Ccelambres. 



Elytral ligula wanting. 



Mesosternum not attaining metasternum Deronectes. 



Mesosternai fork connected with the intercoxal process of 

 the metasternum Hydroporus. 



Desmopachria, Bab. 



D. convexa, Aube, is a small species (.07 in.), rounded and convex 

 in form, and of a shining brownish-red colour without markings. The elytra 

 are finely punctured, the clypeus with distinct margin. I find it here in 

 small creeks or ditches through meadows. 



Bidessus, Sharp. 



Contains two small Canadian beetles of depressed, oblong form and 

 brownish colour, sometimes with paler markings. The thorax and elytra 

 have a common basal striola on each side. 



Nearly unicolorous, punctuation fine (.06 in.) affinis, Say. 



Brownish, elytra with paler shades and coarse punctures(. 06 in. )///5^d!/'«.f,Cr. 



Celina, Aube'. 



The Canadian records give C. angustata, Aube, as an inhabitant of 

 the region, possibly in error, as the genus is characteiistically southern. 

 It is a parallel, elongate insect of a brownish-red colour, the elytra darker, 

 mucronate. The thorax is transverse, gently rounded on the sides, the 

 disk with fine punctures, which become deep in front and on the sides 

 near the base (.14 in.). 



*This is a tongue or raised process on the under surface of the elytra near the outef 

 margin. They must be lifted to show it. 



