THE PREDACEOUS DIVING BEETLES. 



229 



447 ( ). IllIANTUS CONFUSUS Sp. 110V. 



Elongate-oval, rather robust, subdepressed. Above uni- 

 form black, shining; antennae and palpi light reddish- 

 brown ; tibiae and tarsi dark reddish-brown ; under sur- 

 face piceous. Head smooth, the front with two small 

 foveae between the bases of antennae. Thorax more than 

 twice as wide as long, sides feebly curved, margins dis- 

 tinct ; surface with sparse fine punctures near the front 

 and hind margins. Elytra each with four double rows 

 of fine, very confused punctures. Presternum convex but 

 not distinctly carinate along the middle. Length 12 mm. Fig. 113. x 2\. 



(Pig. 113.) (Original.) 



Floyd County - rare. September 28. Described from a single 

 male taken from beneath a stone on the shore of the Ohio River. 

 Under a strong lens the entire upper surface of both this and bis- 

 iriatus is seen to be marked with very fine reticulated lines between 

 which are numerous exceedingly minute punctures, giving it the ap- 

 pearance of being alutaceous. 



XVIII. Colymbetes Clairv. 1806. (Gr., "dive + swim. ") 

 Rather large elongate beetles having the sides of thorax oblique, 

 not margined; scutellum punctate; elytra with very fine transverse 

 striae. The males have the anal segment triangularly emarginate 

 and joints 2 and 3 of front and middle tarsi clothed with small 

 equal disks. One species occurs in Indiana. 

 448 (1474). Colymbetes sculptilis Ilarr., N. Eng. Far., 1829, 8. 



Elongate-oval. Vertex black with two small paler spots ; 

 thorax, front of head and margins of elytra dull yellow, 

 the thorax with a black transverse discal bar; disk of 

 elytra darker; under surface black, legs and hind mar- 

 gins of abdominal segments reddish-brown. Length 16 mm. 

 (Fig. 114.) 



Occurs sparingly along the shore of Lake Michi- 

 gan ; not noted elsewhere but should occur. May 



Fig. 114. X If ^ Tnnp 9fi 

 (After Wickham.) O-JUne Zb. 



Tribe III. DYTTSOINI. 

 Diving beetles of large or medium size, easily distinguished by 

 the peculiar dilated form of the front tarsi of the males. In these 

 the first three joints form a circular cushion with small disks on the 

 under side. The middle tarsi are also frequently dilated, the joints 

 being oblong with variously arranged disks or suckers beneath. 

 Sometimes, as in Acilius, there are three well-marked sizes of disks 

 on the same foot. The tribe is represented in the United States by 

 six genera, five of which occur in Indiana. 



