NORTH AMERICAN COLEOPTERA. 89 



DIABROTICA Chev 



Head not inserted as far as the eyes, front transversely impressed, 

 vertex foveate, a carina between the antenna;. Eyes broadly oval, 

 entire; labrum rather large, truncate, or feebly emarginate. An- 

 tennae slender, at least longer than half the body, sometimes longer 

 than the body, second and third joints often very small ; maxillary 

 palpi moderately stout, the terminal joint conical, shorter and nar- 

 rower than the preceding. Thorax broader than long, sometimes 

 nearly square, the margin distinct, slightly reflexed, disc usually 

 bifoveate ; scutellum acutely oval at tip. Elytra with a very dis- 

 tinct and slightly reflexed side margin, the epipleurge distinct to 

 apex ; anterior coxae contiguous, the prosternum with merely a linear 

 prolongation, the cavities open behind ; metasternal parapleurte long, 

 narrower behind. Legs moderately long and slender ; tibise slender, 

 the middle and posterior pairs with terminal spurs, the outer edge 

 carinate from knee to tip, except in a few species ; first joint of hind 

 tarsus at least as long as the next two, sometimes nearly as long as 

 the next three ; claws bifid. 



Diahrotioa is, with few exceptions, confined to the Western Hemis- 

 phere, represented by many species of varied facies and ornamenta- 

 tion. It is the most numerously represented of all the Galerucide 

 genera of our fauna. 



All attempts to arrange the species have been based primarily on 

 the structure of the antennae with the result of completely confusing 

 the species in their true relations to each other. 



In the majority of the species the second and third joints are 

 small, together .scarcely as long as the fourth, sometimes only half 

 as long ; several species have the third joint nearly or quite as long 

 as' the fourth, while the second remains small. When the third 

 joint is equal, or nearly so, to the fourth, it will be found to be 

 densely punctured and pubescent like the fourth, but when that joint 

 is small it will be found smooth and like the second in structure. 



That some of the species have the tibise carinate, while in others 

 it is not, seems not to have been observed by authors. 



The male sexual characters are feeble. All have the last ventral 

 truncate, and in some broadly emarginate. A few have the first 

 joint of the anterior tarsi dilated. 



Our species seem to divide naturally into three series, and may be 

 determined by the aid of the annexed table : 



TKANS. AM. ENT. SOC. XX. (12) JUNE, 1893. 



