THE WATER SCAVENGER BEETLES. 



257 



VII. Hydrgcharis Latr. 1825. (fir.. 1 Aniter - delight. ? ') 



The .presternum, 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). Hydrochabis obtusatus Say, Journ. Phil. Acad. Nat. ScL, 

 III, 1S23, 200; ibid. II. 129. 



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

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

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

 sternum not extending beyond hind coxa?. Length 13-16 mm. 



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

 ern portion. April 6-September 15. Often taken bereath lags 

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



Tribe III. HVDROBIIXL 



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 GEXEEA OF HYDEOBIIXI. 



a. Last ventral segment emarginate ; antenna? seven-jointed ; elytra with 

 ten stria? ; length 2.5-6 mm. VIII. Beeostts. 



aa. Last ventral segment entire. 



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

 than 2.5 mm. IX. Chjetabtheia. 



Ventral segments not covered. 



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

 length 2.5-3 mm. X. Laccobius. 



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



<L Last joint of maxillary palpi shorter than third; length 3.5- 

 7 mm. 



e. Tarsi five-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. XL Philhydeus. 

 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. Helochaees. 

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



g. Mesosternum with a feeble transverse carina ; tarsal claws 



simple; elytra not striate. XIII. Cyvtbiodyta 



