TRIBE III. IIYPERIXI. 153 



wider than long, apex one-fourth narrower than base; disc closely covered 

 with granuloid tubercles which are small above, larger and rugose on the 

 sides; median carina fine, reaching the base. Elytra oval, one-half longer 

 than wide; striae deep, narrow; intervals tuberculate as thorax, tips con- 

 jointly rounded. Mesosternum, elevated between the coxa?. Length 9 

 11.2 mm. 



A European species recorded by Hamilton as occurring 1 in 

 Michigan. 



L. gemellus Kirby, described from Alaska, having the thorax as long 

 as wide, coarsely granulate, strongly carinate, elytra without antemedian 

 pale spot, but with a line of white hairs along the strife, intervals coarsely 

 rugose, alternating strongly in width and feebly in convexity; length 12.5 

 mm., has been recorded from the Hudson Bay Region of Canada. 



IV. LISTRONOTUS Jekel, 1864. (Gr.. "smooth" 4- "back.") 



Medium sized, usually dirty brown species, 5 or more mm. in 

 length, having the ocular lobes of thorax prominent, partly con 

 cealing the eyes in repose; first, second and fifth ventral seg- 

 ments long, third and fourth very short ; legs slender, tibiae bent 

 inward at tip and rather strongly mucrouate. Male with first 

 and second ventrals more or less flattened and concave, and anal 

 segment often so convex as to project behind the last ventral and 

 become visible from beneath ; female with elytra often either sub- 

 acute or more or less prolonged at tip, and with fifth ventral 

 often impressed or otherwise modified. All the species whose 

 habits are known breed in semiaquatic plants and many of them 

 are readily attracted by light. For convenience our Eastern 

 species are separated into two groups as follows : 



KEY TO GROUPS OF EASTERN SPECIES OF LISTRONOTUS. 



a. Funicle of antennae slender, third joint distinctly longer than fourth; 

 second joint two or three times longer than first; length 7 14 mm. 



GROUP I. 



aa. Funicle less slender, the third and following joints rounded, sub- 

 equal; second joint three times as long as first; subapical callus of 

 elytra feeble or obsolete; length usually less than 8 mm. GROUP II. 



GROUP I. 



This group comprises our larger species and the ones in which 

 the secondary sexual characters of the female are most strongly 

 developed, that sex being much easier to determine than the male. 

 For example, the males of camJatus are very similar to those of 

 callosits and are distinguished only by the feeble callus near the 

 elytral declivity, whereas the females of the two species are easily 



