U2 



Bulletin No. 159 



pose. In the swift streams of mountain regiors these 

 beetles of the family Hydrophilidae and Dytiscidse are not 

 commonly seen. They appear not to endure buffeting well 

 enough to hold their own in such waters. But their places 

 are taken by others which are perfectly able to take care of 

 themselves in the swiftest currents. One of the whirligig 

 beetles was observed repeatedly in both creeks and rivers, 

 often lurking in sheltered nooks among partly submerged 

 rocks, but striking out in the swift current if pursued and 

 when pressed diving to the bottom. These beetles are ex- 

 clusively aquatic, their form and flattened middle and hind 



Fig. 21.— Expanded legs ot the whirligig beetle, Dtneutes dtscolor. 

 a, right hind leg; /', right middle leg. Greatly magnified. 



legs rendering them strong swimmers and unsuiting them 

 for locomotion on the land. They have four compound 

 eyes, or at any rate four independent divisions, two looking 

 downward in the water and two looking upward. 



The only species collected was Dineutes discolor. It is 

 shining black with an olivaceous cast, in some lights with 

 purple and bronzy reflections, especially about the head and 

 the anterior edges of the wing covers. Eyes in preserved 

 examples, reddish brown. Body rapidly contracted forward 

 from the middle of the wing covers and meeting evenly 

 behind with angles little evident and margin not serrulate. 

 Labrum protruding, rounded, with a dense silken white 



