AKT. 23 REVISION OF THE BEETLE GENUS OEDIONYCHIS BLAKE 3 



described by von Harold from " California," has not since been 

 identified. Four species are known to occur in Canada. 



Specimens have been examined from the United States National 

 Museum, Philadelphia Academy of Natural Sciences, Museum of 

 Comparative Zoology, Boston Society of Natural History, University 

 of Kansas, British Museum, and Museum of Natural History at 

 Paris. At the last-named museum, where M. P. Lesne and his asso- 

 ciates courteously placed the collections at my disposal, I had oppor- 

 tunity during the summer of 1925 to examine the old Bosc collection, 

 in which are several specimens considered by M. Lesne to be cotypes 

 of species described by Fabricius. I wish to express my thanks to 

 the curators of the collections mentioned for the opportunity to 

 study the specimens in their charge, to Dr. A. G. Boving for his 

 description and drawing of the larval stage, to Dr. F. H. Chittenden 

 for his encouragement in this study, and to Dr. E. A. Schwarz and 

 Mr. H. S. Barber for their constant assistance and advice. 



DESCRIPTION OF THE GENUS 



The main characters differentiating the genus Oedionychis from 

 related genera are (1) the swollen, globular claw joint of the hind 

 tarsus and the comparatively short first joint of the posterior tarsus ; 

 (2) the confusedly punctate or smooth and glabrous elytra; (3) 

 the open coxal cavities; and (4) the wide prothorax. not much nar- 

 rower than the elytra. 



The genus is composed of species widely dissimilar in general 

 appearance. The North American species range in length from 3 to 

 8 mm., and there are larger species in tropical America. In color 

 they vary from pale, almost waxen, to lustrous metallic green, blue, 

 or purple, and even opaque black; they may be concolorous, spotted, 

 vittate, or transversely banded. 



The head is usually exposed to the eyes. The prothorax is always 

 considerably wider than long, has a more or less explanate margin,^ 

 and has usually dentiform anterior angles. The scutellum is either 

 small and triangular, or in the larger, more convex species, rounded. 

 The elytra are sometimes very narrowly, sometimes widely explanate. 

 At base the elytra are not much wider than the prothorax, but widen 

 ovately in some species, and in others are broadly or narrowly ob- 

 long. The punctation when present is always confused, never 

 striate; frequently the surface is nearly impunctate, never pubes- 

 cent. The body beneath is usually lightly pubescent. The epipleura 

 vary with the width of the explanate margins, the species with broad 

 margins having wider epipleura reaching nearly to the apex. The 

 legs are relatively short. The posterior legs have the femora much 

 thickened, with a little tooth just above the tarsus on the tibiae, 



