278 
NORTH AMERICAN GYRINUS (cOLEOPTERa) 
l''()i iii ratluM- la-oader, siirfafo luster, especially of the female, less strongly 
shining; middle lobe of oedeagus laterally com[)ressed apically so that it 
appears at I ip to he wider when viewed from the side than from above. 
27. lugeiis 
Tpper surface distinctly aeneous, anal segment conspicuously rufous; 
form rather narrow, size smaller 2S. aiKilis 
2cS. Tarsal claws yellowish 29. nixicufi 
Tarsal claws piceous 29 
29. lTpi)er surface distinctly and rat luu- closely micro-])unct ulate. MO. vallisi 
Upper surface not a.ppreciably micro-punctidatc' MO 
30. Form moderately gibbous in profile Ml. frosii 
Form very thick, strongly gibbous 32. gibber 
31. Sides of thorax and elytra less continuous than usual; first ventral seg- 
ment shorter, the fifth longer than in other species. . 33. itnpressicolUs 
1. Gyrinus minutus Linnaeus 
Small, narrow, moderately convex; above black, sides bronzed, surface 
throughout strongly reticulato-alut;iiceous and dull; beneafh testaceous or 
brownish testaceous, the ventral segments except the apical one commonly 
more or le.ss infuscate; scutellum very finely longitudinally carinate basally; 
me.'^osternum distinctly rather deeply sulcate. 
Male genitalia. Color brownish apically, paler basally; middle lobe about 
as wide apically as the lateral lobes, narrowly rounded and minutely notched 
at fip. 
Length, M.f) to 4.3 mm.; width, l.S to 2.3 mm. Average lenglh close to 4 
mm. 
A coiniiioii species, oeeurring’ throughout Central aiul North- 
ern Euroi)e and in Siberia. In North America it ranges entirely 
across the continent from Maine to Alaska. 
Specimens at hand are from Alonmouth, Maine (Frost); 
I lolderiK'ss, New Hampshire (A. P. Alorse); Northern Illinois; 
Diiaga, Kansas; Prookings and Volga, South Dakota; Le Pas, 
Picpiitmiay Piver, Mile 250 Hudson Pay Paihvay, and Kettle 
Pai)ids, Manitoba (Wallis); kldmonton, Alberta (C'arr); Homer, 
-Maska (W. S. McAliiinc). 
d'lu' small size and dull sui'face luster instanlly distinguish 
this w('ll known species from all others of our fauna except tlu' 
next, which s('e for a statement of differences. The carina of 
I he scut('lluni is lunu'r very cons])i(‘uous, and consisls of a. V('ry 
shot I leebh' (‘h'vation close' lo lh(' thoracic mai'gin. 
