208 FAMILY TV. DYTISCID^E. 



mi. Last joint ol' ma \ill;i ry palpus triinratM; prostprna I (.I|-"PRS ver.y broad 

 behind the <-o\.-p; hind tibi:e broader; length 4-5 mm. 



II. HYDROCANTHUS. 



I. CANTHYDBUS Sharp. 1882. (Gr., "beetle + water.") 



Small and short, strongly convex species, usually variegated in 

 color above ; antennae very short and slender ; pectoral plate coarsely 

 sculptured at middle ; hind legs slender, the femora and tibiae but 

 little flattened, the former contiguous at base. Two species occur 

 in the State. 



393 (1237). CANTHYDBUS BICOLOB Say, Trans. Amer. Phil. Soc., IV, 1834, 



447 ; ibid. II, 561. 



Ovate, convex. Head, thorax and under parts reddish-yellow ; elytra 

 dark reddish-brown, thickly and rather coarsely punctate. Length 2.5 mni. 



A small but handsome species, taken in Indiana only from Bass 

 Lake, Starke County, and Hudson Lake, Laporte County. Prob- 

 ably occurs throughout the lake region of the State. May 30-Au- 

 gust 20. 



394 (1238). CANTHYDBUS GIBBULUS Aube, Spec. Gen., VI, 1838, 414. 

 Ovate, convex. Head and thorax yellow, the latter clouded with dusky 



on the front margin ; elytra dark brown or piceous, with an irregular oblique 

 yellowish cross-bar near the middle. Elytra more sparingly punctate than 

 in Incolor, the dorsal rows of punctures more distinct. Length 2.5 mm. 



Beneath rubbish on beach of Lake Michigan, near Pine, Lake 

 County; scarce. August 1. 



II. HYDROCANTHUS Say. 1823. (Gr.. "water -'-beetle.") 



In addition to the characters given in the key. this genus may b 

 known by having the last joint of the labial palpus very large, tri- 

 angular and compressed; the front tibia 3 with a strong spur; the 

 hind femora short and stout, th'-ir apical margins strongly ciliated; 

 tibia- 1 short, smooth, claws equal. But one species is known from the 

 United States. 



.'I'.tn (1240). HYDBOCANTIIUS IEICOLOK Say, Trans. Amer. Phil. Soc., II, 182.' 1 ., 



105 ; ibid. II. 517. 



Ovate, convex, attenuate behind. Head, thorax and under parts red- 

 dish-yellow; elytra dark reddish-brown, polished, iridescent. Three irregu- 

 lar dorsal rows of fine punctures visible. Length 4-5 mm. 



Throughout the State; frequent. March 16-August 15. Prob- 

 ably hibernates, as one was taken from mud at the bottom of a pond 

 on the earlier date. 



