222 



FAMILY IV. DYTISCIDJE. 



X. Ilybius Er, 1832. (Gr., "mud + life. " ) 

 Oblong, convex black or metallic beetles of medium size, having 

 the thorax margined and the prosternal spine compressed and 

 acute. The males have the front and middle tarsi compressed, 

 thickly fringed beneath, the claws equal, the anal segment often 

 carinate; female with anal segment emarginate. The upper sur- 

 face, when viewed with a lens, is seen to be finely reticulate, while 

 beneath they are finely strigose. On the sides of the elytra are two 

 small pale spots, one of which is subapical. 



Two species have been taken in Indiana while three others may 

 occur. 



KEY TO INDIANA SPECIES OF ILYBIUS. 



a. Hind tarsi of males with the joints margined at the outer lower edge ; 

 all four spots of elytra distinct. 



b. Last ventral segment of male acutely carinate; above dark reddish- 



brown. 429. IGNAEUS. 



bl>. Last ventral of male not carinate, its apical portion with coarse 

 lengthwise striae; upper surface greenish-bronzed, metallic. 



SUB^ENEUS. 



aa. Hind tarsi of males not margined at the lower outer edge. 



c. Last ventral of male carinate; one or both elvtral spots very faint. 

 d. Black, slightly bronzed ; elytra without reddish marginal stripe. 



430. BIGUTTULUS. 



dd. More strongly bronzed ; elytra with reddish margins. 



FRATERCULUS. 



cc. Last ventral of male not carinate; elytra with margin broadly red 

 from the humeri to beyond the middle. confusus. 



429 (1385). Ilybius ignabus Lee. Proc. Phil. Acad. Nat. Sci., 1862, 521. 

 Elongate-oval, not dilated at middle. Dark reddish-brown; margin of 



elytra slightly paler, the front spot linear; legs piceous. Front tarsal claws 

 of male distinctly sinuate beneath. Length 8-9.5 mm. 



Shore of Lake Michigan near Pine, Lake County; rare. May 

 25. Also one specimen marked "Ind." in Webster collection. 



I. subceneus Erichs., 11.5 mm. : /. fraterculus Lee, 10.5 mm., and 

 /. confusus Aube, 11 mm. in length, are all members of the boreal 

 fauna which have been taken in Michigan and perhaps occur in 

 northern Indiana. 



430 (1389). Ilybius biguttulus Germ., Ins. Sp. Nov., 1824, 29. 



Oval, convex, slightly dilated at middle. Antennae and front and mid- 

 dle legs, reddish-brown; under snrfnee and hind legs piceous. 

 Length 10-11 mm. (Fig. 111.) 



Lake, Laporte, Starke, Vigo and Fountain coun- 

 ties; probably throughout the State; frequent. April 

 23-October 6. When caught with the fingers it ex- 

 Fig. in. udes from the under side a white milky substance. 



