2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 82 



The earlier species of Disonycha — caroliniana, glabrata, conjugata, 

 coUata, and discoidea — were described by Fabricius in the genera 

 Crioceris^ Chrysomela, and Galleruca. Later he referred them all 

 to Galhriica, with the exception of Grioceris collata^ the only one 

 having blue, unicolorous elytra, and Ghrysomela discoidea^ not a 

 vittate form. Olivier (1789)'' placed caroliniana and glabrata^ and 

 later ^° conjugata and collata^ in Altica, a name emended by Illiger 

 (1807) to Haltica, and this name in one spelling or the other was 

 used for species of Disonycha, as well as other flea beetles, till long 

 after the publication of the Dejean Catalogue, not only in European 

 works but in descriptions by the early American coleopterists Harris, 

 Say, and LeConte. Melsheimer ^^ (1847) was the first in America 

 to describe a species under the name Diso7iycha, and he used the 

 same generic name in his catalogue of 1853 with 19 specific names 

 listed. In Europe the name Disonycha appeared in the Sturm 

 Catalogue (1843) and in a description by Mannerheim.^^ Clark 

 (1865)^^ redefined the genus, and Crotch (1873)" constructed the 

 first table of United States species, which contained 11 species and 

 1 variety. Since then, von Harold, Baly, Jacoby, and Weise have 

 described many new species from South and Central America, and 

 Jacoby, Casey, Horn, Blatchley, and Schaeffer have added 22 new 

 specific names for North American forms. Horn's treatment 

 (1889)^^ of the Halticinae is the only work in which the genus as 

 a whole, as it occurs north of Mexico, has been studied. Horn rec- 

 ognized 18 species, a number raised to 32 in the present revision. 



The present paper is not written for the purpose of describing 

 new species. In fact, only 2 new species and 3 new varieties are 

 described. It is rather an attempt to create order in a genus in 

 which, on the one hand, too many specific names have been based 

 on differences in coloration unaccompanied by structural charac- 

 ters and, on the other, too many distinct species have been referred 

 to synonymy. Furthermore, an attempt has been made to show the 

 relationship of the species among themselves and the variations in 

 a given species over its entire range. 



DESCRIPTION OF THE GENUS 



Disonycha, as a genus, has long been loosely defined because of its 

 few outstanding characters. In order to include such diverse groups 

 as at present make up the genus, the definition must necessarily be 



"Olivier Encyclopedie m^thodique, vol. 4 (Insects, vol. 1), p. 105, 1789. 



M Olivier, Kntomologie, vol. 6, pp. 686, 702, 1808. 



" Mclshoimev, Pioc. Acad. Nat. Sci. I'liiladelpliia, vol. 3, p. 163, 1847. 



12 Mannerheim, Bull. Soc. Imp. Moscou, vol. 16, p. 311, 1843. 



" Clark, Jouin. Eiit., vol. 2, no. 13, p. 401, 1865. 



" Crotch, Proc. Acad. Nat. Sci. Philadelphia, vol. 25, p. 64, 1873. 



« Horn, Trans. Amer. Ent. Soc, vol. 16, p. 200, 1889. 



