THE WATER SCAVEXGEE BEETLES. S.) i 



VII. HYDROctrARis Latr. 182.3. (Clr., "water + delight.") 



The prostM'Duni. instead of being grooved for the reception of 

 the front end of the sternal ercst. is entire and raised into a sharp 

 carina. One species occurs in the State. 



i'JT (1597). Hydkochakis obti satis t<a.v. Jnvirn. I'liil. Acad. Nat. Sci., 

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

 Male elongate-oval; female oblong-oval, very obtuse l)ehind. Black, 

 shilling ; under surface darlv reddish-broT\Ti, pubescent. Elytra each with 

 four rows of distinct punctures, the outer r(jw double. Spine of nieta- 

 stermim not extending beyond hind eoxai. Length ]:!-l(j mm. 



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

 ern portion. April 6-Scptcmher 15. Often taken hereath logs 

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



Tribe III. IIYDUOBIIXI. 



Aquatic beetles of small size and of an oval or hemispherical 

 form, having the thoi'ax at base always as wide as the base of elytra, 

 and tlie metasternal spine never prolonged back of the hind coxa-. 

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

 Dr. Horn as follows : 



KEY TO I^IUIA^'A GENEEA OF HY'DKOBIINI. 



a. Last ventral segment emarginate ; antenn;e seven-jointed ; elytra with 

 ten strife; length 2.5-6 mm. VIII. Bebosus. 



aa. Last ventral segment entire. 



6. First and second ventral segments concealed liy plates; length less 

 than 2.5 mm. IX. Ch^etabtheia. 



66. Ventral segments not covered. 



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

 length 2.5-3 mm. X. Laocobiis. 



cc. Antennai nine-jointed ; color usually dark. 



il. Last joint of maxillary palpi shorter than third; length 3.5- 

 7 mm. 

 e. Tarsi five-jointed on all the feet. 



f. ilesosternum with a lojigitudinal lamina or plate ; second 

 joint of maxillary palpi curved, with the ccmvexity to the 

 front; elytral punctures c(]nfused. XI. Philhydrus. 



ff. Jlesostei-num with only a slight median tuberosity ; con- 

 vexity of the curved seeond joint of maxillary palpi turned 

 to the back ; elytral punctures in rows. 



XII. Helochares. 

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



fl. JlesosternuiM with a feeble transverse carina ; tarsal claws 

 simple; elytra not striate. XIII. CvirBiODY'TA 



