THE PREDAOEOUS DIVING BEETLES. 



233 



the margins; elytra with the margin broadly yellow and usually with a 

 sub-basal yellowish band from which extend backward four or five narrow 

 dull yellow lines; under surface dark pieeous, the prosternum paler. Length 

 12.5-14 mm. 



Lake and Steuben counties : rare. May 27-August 16. 



455 (1478). Hydaticus leyipennis Thorns., Op. Ent.. Ill, 324. 



Elongate-OYal, subc-omrex. Pieeous aboYe and beneath ; front of head, 

 thorax except a basal cross-bar. front and middle legs and antennae reddish- 

 yellow ; side margins of elytra dull brownish-yellow: middle tibiae pieeous. 

 Dorsal rows of punctures distinct. Female with tips of elytra slightly pro- 

 duced and subsinuate. Length 12.5 mm. 



One male in Field Museum collection from "Ind.," probably 

 St. Joseph County. The dark basal cross-bar of thorax is widest at 

 middle and tapers to a line each side. 



H. bimarginatus Say, 12 mm. in length, occurs from Ohio to 

 Georgia and Florida. 



XXI. Acilius Leach. 1817. (L., a Koman name.) 



Medium-sized subdepressed. species, slightly oboyate in 

 form, and having the upper surface distinctly and regu- 

 larly punctate; thorax not margined; hind coxa? very 

 large. Females with elytra either sulcate or smooth. 

 Males with front tarsi broadly dilated, with one large and 

 two small disks beneath, the middle tarsi simple, the 

 hind claws equal. (Fig. 118. ) Two species have been 

 taken in Indiana, while one other may occur. 



118. 



Comstock.) 



KEY TO INDIANA SPECIES OF ACILIUS. 



a. Vertex with a distinct M-shaped black mark ; sulci of female elytra un- 

 equal in length, the outer ones longer and reaching nearly to base. 

 1). Hind femora reddish-brown; length 12.5-14 mm. 



456. SEMISULCATUS. 



1)1). Hind femora black ; length 12 mm. mediates. 

 aa. Vertex without an M-shaped mark; sulci of female subequal in length 

 and reaching only to middle of elytra; length 13-15 mm. 



457. EKATERXUS. 



456 (1492). Acilius semisulcatus Aube. Spec. Gen.. 

 VI. 1S3S. 132. 

 Broadly oval or oboYate. Dull brownish-yellow aboYe ; 

 head with base and an M-shaped mark on Yertex 

 black ; thorax with two transYerse black lines on 

 disk, the front one the wider; elytra closely marked 

 with black dots and with subapical yellowish cross- 

 bar. Length 12.5-14 mm. (Fig. 119.) 



Lake, Marshall, Marion and Vigo counties 

 frequent, June 12-August 15. 



Fig. 119 X 2. 

 (After Wjckham.) 



