4 NORTH AMERICAN 



elevation are entirely absent, and the surface between the eyes evenly 

 flat or curved throughout. Antennae varying but slightly, 11 -jointed, 

 sometimes rather long and strongly clubbed (Dianous), in two species 

 (sub-gen. Mutinus) long and very feebly enlarged toward the tip, 

 generally distinctly clubbed and slightly longer than the width of 

 head; first two joints always more robust than the funicle, inserted 

 upon the front under slight tuberculations of the upper surface. 

 Maxillary palpi generally very well developed, first joint shortest and 

 almost invariably palest in color, third joint longest, more or less 

 strongly and gradually enlarged toward the tip, fourth extremely 

 minute, generally spinous, acute, and seldom visible, except under 

 favorable conditions and under the high powers of the microscope. 

 Labial palpi very small, second joint very robust, third spiniform and 

 minute. Maxillae short, lobes membranous toward tip, where they 

 are densely and coarsely ciliate. Mentum trapezoidal, nearly trans- 

 versely truncate anteriorly, having upon its exposed surface a strongly 

 elevated, triangular process, separated from the base of the mentum 

 by a transverse, curved canaliculation ; apex of the triangle acute 

 and generally projecting slightly beyond the anterior margin of the 

 mentum ; sides of triangle generally incurvate ; the mentum usually 

 bears several setae irregularly disposed. Ligula membranous. Man- 

 dibles long, arcuate, acicular toward the tip, which is very acute; 

 having internally near the apex, a long, very acute, recumbent tooth, 

 which, however, is sometimes shorter and robust. 



Prothorax usually more or less elongated, always strongly convex, 

 and sometimes sub-cylindrical, often longitudinally canaliculated, and 

 more or less tuberculate at the base. 



Elytra wider than the prothorax, generally longer than wide, 

 moderately convex, usually more or less impressed along the suture, 

 more particularly toward the base, also often impressed near the 

 humeri, thus giving the appearance of a slight longitudinal tubercula- 

 tion near the middle of the base of each elytron ; together broadly 

 and more or less feebly emarginate behind ; sides more or less diver- 

 gent posteriorly, generally slightly arcuate. 



Abdominal segments seven in number, usually decreasing in width 

 posteriorly, sometimes (Areus advena), with the fourth and fifth seg- 

 ments wider than the first and second. Each dorsal segment has at 

 the base, a transverse elevated ridge, which generally has several 

 cusped prolongations posteriorly. 



Legs variable in length, generally rather long and somewhat slender, 

 always pubescent. Tibiae usually nearly equal in thickness through- 



