ART. 2 REVISION OF TRIRHABDA NORTH OF MEXICO BLAKE 9 



History; C. A. Frost; E. T. Cresson, jr., of the Academy of Nat- 

 ural Sciences of Philadelphia ; Dr. T. H. Frison, of the Illinois State 

 Natural History Survey; H. P. Loding, Prof. H. B. Hungerford, 

 and Warwick Benedict, of the University of Kansas; Prof. Paul 

 Johnson, of South Dakota College; Prof. Franklin Sherman, of 

 Clemson College; Ralph Hopping; and F. S. Carr. I am also in- 

 debted to my associates in the United States National Museum, par- 

 ticularly to H. S. Barber and L. L. Buchanan, who have given me 

 freely their welcome criticism and advice. 



KEY TO GENERA 



1. Third and fourth auteiiual joints approximately equal or third 



slightly the longer ; a distinct ridge or sulcus on outer edge 



of tibia extending its entire length 2 



Third antenual joint distinctly shorter than fourth ; sulcus on 



outer edge of tibia indistinct, not extending its entire length 3 



2. Body dilated posteriorly ; prothorax more than twice as broad 



as long, with arcuate sides ; antennae not longer in male Monocesta 



Body parallel ; prothorax subquadrate, scarcely twice as broad 

 as long, sides tending to be straight or slightly angulate at 

 middle ; antennae longer and more robust in male Coraia 



3. Aedeagus short, truncate ; prothorax considerably more than 



twice as broad as long ; head glabrous Derospidea, new genus 



Aedeagus long, acute at tip ; prothorax approximately twice as 



broad as long; head pubescent Tririiabda 



KEY TO THE SPECIES OF TRIKHABDA 



1. Occipital and pronotal spots and elytral vittae piceous or black 



without metallic luster , 2 



Occipital or pronotal spots or vittae or entire elytra except for 



margin dark with metallic luster 12 



Occipital and pronotal spots and remnants of elytral vittae 



reddish brown to piceous. Species of the arid Southwest 29 



2. Pronotal surface between coarse punctures smooth and shining 3 



Pronotal surface between coarse punctures alutaceous 4 



3. Elytra coarsely punctate, with short, very sparse pubescence; 



sutural vitta only a narrow darker border of sutural edges, 

 lateral vitta narrow, more or less evanescent ; pronotum 

 usually coarsely punctate, not polished. Owens Valley, 



Calif caduca (p. 31) 



Elytra finely punctate, finely and densely pubescent; sutural 

 and lateral vittae usually united at apex ; pronotum sparsely 

 punctate, polished. Rocky Mountains and southern Cali- 

 fornia nitidicollis (p. 23) 



4. Elytra with lateral and sutural vittae united before or slightly 



behind middle or with traces of utedian vitta coalescing with 



lateral vitta 5 



Elytra with lateral and sutural vittae distinct and not united 

 before apex, no median vitta 7 



54290—31 2 



