THE WATER SC'AVKMiER BEETLES. 257 



VII. HYDROCIIARIS Latr. IS:T>. 4r., "water f delight." ) 



The prosternuni. instead of being grooved for the reception of 

 the front end of the sternal crest, is entire and raised into a sharp 

 carina. One species occurs in the State. 



497 (1597). HYDBOCHARIS OBTI SATTS Say. Journ. I'liil. Acacl. Nat. Sci.. 

 Ill, 1823, 200; ibid. II, 129. 



Male elongate-oval; female obloug-oval, very obtuse behind. Black. 

 shining; under surface dark reddish-brown, pubescent-. Klytra each with 

 four rows of distinct punctures, the outer row double. Spine of nu-ta- 

 sternum not extending beyond hind coxae. Length 13-KJ nun. 



Common throughout the northern half of State; less so in south- 

 ern portion. April 6-Septemk-r 15. Often taken be:' eat h l:igs 

 and stones close to the edge of water; also at electric light. 



Tribe III. IIYDROBIINI. 



Aquatic beetles of small size and of an oval or hemispherical 

 form, having the thorax at base always as wide as the base of elytra, 

 and the metasternal spine never prolonged back of the hind coxa 1 . 

 The tribe is represented in Indiana by nine genera, separated by 

 Dr. Horn as follows : 



KEY TO INDIANA GENERA OF HYDROBIINI. 



a. Last ventral segment eniarginate ; antennae seven-jointed ; elytra with 

 ten strite; length 2.5-6 mm. VIII. BEROSUS. 



. Last ventral segment entire. 



b. First and second ventral segments concealed by plates ; length less 

 than 2.5 mm. IX. CH^ETARTHRIA. 



6&. Ventral segments not covered. 



c. Antennae eight-jointed; color mostly pale; form rounded, convex; 

 length 2.5-3 mm. X. LACCOBHS. 



cc. Antenna 1 nine-jointed; color usually dark. 



'/. Last joint, of maxillary palpi shorter than third; length 3.5- 



7 nun. 

 e. Tarsi live-jointed on all the feet. 



f. Mesosternum with a longitudinal lamina or plate ; second 

 joint of maxillary palpi curved, with the convexity to the 

 front; elytral punctures confused. XI. PHILHYDRUS. 



ff. Mesosternum with only a slight median tuberosity ; con- 

 vexity of the curved second joint of maxillary palpi turned 

 to the back ; elytral punctures in rows. 



XII. HELOCIIARES. 

 ee. Tarsi four-jointed on the middle and hind feet. 



ff. Mesosteruum with a feeble transverse carina ; tarsnl claws 

 simple; elytra not striate. XIII. CYMBIODYTA 



