Till; \\\ri:i; stAvr.\(:i:i; r.iMyi'LKS. 249 



Horn. — "Notes on sdiiic 1 1 ydi-oliiini i>l' I'.oi'cal AiiicricM, " loc. 



(it., 237-278. 

 Ifoni. — "A l\c\isi(iii of llic Splia'i'idiiiii I iilwihitiniz: I-Joi'cjiI Amci'- 



ii'a," h>c. (11., 27i)-;n4. 

 Wiclhaw. — "Tlic Hydfopliilida' (A' Oidai-io and Quehcc," In 



Can. Ent.. XXVI I. IS!).'). ISI. 21.;. 



About 170 sjiocics of Ilydiophilidu' ai'c Iokuvii I'l-oiii tho (Tnitcd 

 Slates. Tlioso ai'c dislrihidcd aiiioiiii' I'lmr tribes, all (d* wbidi at'o 

 i'('|ti'('S('iit('d ill Indiana. 



KEY TO I'KlliKS OF II V DKOl'II II.ID.E. 



(/. Thora.x narrower tli.TU elytra, usually uarrowed behind; form cloniiate; 

 sculpture usually rou.i^li ; len.i^th less than nun. 



Tribe I. Helophorijni. p. 24!). 

 (/(/. Thora.x at base as wide as elytra, narrowed in front; form usually eon- 

 vex, oval or elliittieal; seidiiture usually weak. 

 h. Middle and hind tarsi with lirst joint short. 



c. Metasternum prohinired into a distinct spine; tarsi compressed. 



Tribe II. Hydrophiltni, p. 254. 

 cc. Metasternum not prolonged; tarsi not compressed. 



Tribe III. PIydrobiini, p. 2.17. 

 hb. Middle and hind tarsi with the first .ioint elcmgated; length less than 

 :'...■» mm. (except in .'^jilniridiiim ). 



Tribe IV. Sph.eridiini, p. 2(;.5. 



Tribe I. IIELOPIIORINI. 



Small oblopo' or elongate a(|uatie sj)oeies. gray or brown, more or 

 h'ss tinged with bronze in color. They oeeiir in pools, where the}' 

 cling- to aquatic plants and may be readily taken by stirring up the 

 innd and plants at the bottom, when the beetles will rise to the sur- 

 face. They swim but poorly and are itnable to dive rapidly. Of 

 the five genera into which the tribe has been separated, representa- 

 tives of four occur in Indiana. 



KEY TO IM)I.\X.A (iE.XER.V OF Tn'.r.OlMIORI XI. 



(/. Elytra with ten stria- or rows of punctures; inaxillary ])alpi moderate. 

 h. Last joint of maxillary palpi longer tiian the next to last. 



c. Antenna' nine-jointed. I. IIeloimiorl's. 



cc. Autenuio seven-jointed. II. IlYnRociics. 



J)h. East joint of inaxillary palpi shorter than the next to last. 



III. OCUITII'.IUIS. 



(III. Elytr:i with more than ten rows of imnetures; m;ixillary ]ial]pi very long. 



ly. IIVI)K.EN.\. 



