6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 82 



a more artificial but all-inclusive key, based mainly on color dif- 

 ferences, appended for practical use in the identification of the 

 species. 



The first group, the pensylvanica group, is composed of 5 northern 

 species, j)ensylvanica^ conjugata, procera, uniguttata^ and limbicoUis, 

 and at least 1 Mexican and Central American species, recticollis. 

 All of them feed on Polygonum. They are slender, oblong insects 

 with parallel sides, often with the dark elytral vittae broader than 

 the pale ones, and with the head and under surface more or less 

 darkened. The pronotum is usually uneven and the elytra of the 

 female distinctly costate. The aedeagi are quite unlike one another 

 in the shape of the dorsal tip, but the differences are more a matter 

 of degree than of radical change in shape. 



The second group, the alternata group, is composed of four 

 northern species, alternata^ pluriligata, latiovittata^ and schaefferi^ 

 and a fifth, teapensis, described from Teapa, Mexico. The first four 

 are known to feed on willow. These are the largest of the genus 

 (6 to 8" mm) and are broadly oblong with parallel sides. The head 

 is usually coarsely punctate and, as in the pensylvanica group, but 

 to a less degree, the pronotum is uneven and the elytra of the female 

 show traces of costation. The aedeagi differ in the shape of the 

 tip but their differences, as in the pensylvanica group, are merely 

 relative. 



The third group, the fumata group, is composed of two species, 

 fumata and latifrons^ each with several geographic races. As far as 

 known, they feed on Aster and Solidago. They are more oval in 

 shape than the preceding groups, with smooth, not depressed or 

 uneven, prothorax, and with no traces of elytral costae. The aedeagi 

 of both species are very similar, but the tip in latifron's, is wider. 



The fourth group, the discoidea group, is composed of three closely 

 related United States species, discoidea,^ leptoUneata^ and antennata, 

 as well as the still undistinguished Mexican and Central American 

 species that were called abhreviata Melsheimer in the Biologia Cen- 

 trali-Americana. Except for discoidea., which feeds on Passi-jiora 

 sp., the food plants of this group are unknown. The species, while 

 differing greatly in markings, are so similar in structure that it is 

 not easy to determine their specific differences. They may be but 

 varieties of one species. All are broadly oval in shape with smooth, 

 undepressed upper surface, the head is nearly impunctate, having a 

 large fovea near each eye, and the pronotum is smooth and usually 

 unspotted, and all either entirely lack the submarginal elytral vitta 

 or show only faint traces of it. The aedeagi are so much alike as to 

 be hardly distinguishable. 



The fifth group is composed of species that have blue or green 

 elytra and that feed on Ainaranthus and Chenopodiwn., and consists 



