201 



1 \ M [LT IV. DYTISCIDyE. 



389 (1231). Cnemidotus 12-punctatus Say, Trans. Amer. Phil. Soc., II, 

 1823, 106 ; ibid. II. 518. 



Ovate, very convex. Dull yellow, each elytron with six 

 well defined black spots arranged as in the accompanying 

 figure. Head finely, thorax rather coarsely and sparsely, 

 punctate. Elytra each with eight rows of large black punc- 

 tures and two rows of finer, paler ones on sides. Hind coxal 

 plates subangulate on hind margin. Length 3.5-4. (Fig. 

 103. ) 



Northern half of State, common ; less so in the sonth- 

 (AftCTWickhlm.) erri comities. Often taken in numbers when seining. 

 May 2 5- August 15. 



390 (1233). Onemidotus edentulus Lee. New sp. N. A. Col., I, 1863, 21. 

 Slightly more elongate and less convex than 12-punctatus. Pale straw 



yellow. Elytra more attenuate behind the middle and with spots larger, 

 often more or less confluent. Length 4 mm. 



Lake. Laporte. Marshall and Fountain counties ; scarce. April 

 29-August 15. 



391 (1232). Onemidotus muticus Lee. New Sp. X. Am. Col., I. 1863, 21. 

 Resembles 12-punctatus in form and sculpture. Differs by having the 



hind femora wholly piceous or dark brown, the hind coxal plates broadly 

 rounded, and the elytra subtruncate at apex. The sutural black line is 

 narrowed on basal half and the median subsutural spot is confluent with it 

 to form a rather large irregular blotch. Length 3.5-4 mm. 



Throughout the State; common. March 14-October 23. This 

 as well as the other species probably passes the winter as imago. 



392 (- ). Cnemidotus pedunculitis Roberts MS. 



Very close to the preceding. Differs mainly in the arrangement of the 

 elytral spots as mentioned in key. The sutural black line is wider, occupy- 

 ing the sutural interval on the basal half, and is not confluent with the 

 median spot. The elytra are feebly sinuate rather than subtruncate at 

 apex. Length 3-3.5 mm. 



Laporte. Marshall, Fountain. Marion and Lawrence counties; 

 scarce. May 11-October 23. 



Family IV. DYTISCIDiE. 



The Predaceocs Diving Beetles. 



In the quiet, deep pools of streams, and in ponds or stagnant 

 water may often be seen oval, flattened beetles hanging head down- 

 ward, with the tip of the abdomen at or slightly above the surface 

 of the water. These beetles belong to the family Dytiscidse, the 



