THE INSECT FAMILY DELPHACIDAE— CRAWFORD. 603 



These ''genera," Delphax, Libumia, Megamelus, Kelisia, Chloriona, 

 Euidella, and ProMisia, are so closely related and intergrade so 

 completely that it is- quite impossible to draw any generic line between 

 the species constituting these groups. The principal characters here- 

 tofore used for this purpose have been the relative distinctness and 

 the trend of the cephalic and notal carinas, the shape of the vertex 

 and frons, and the form of the fore wings. All of these charactei-s are 

 very variable and inconstant, and any generic distinction between 

 species based on them is purely arbitrary and very confusing, and, 

 moreover, it is quite apparent that no two students would agree on 

 the lines of division. 



To a certain extent, however, these characters may be employed 

 to divide very loosely the large genus Megamelus into a number of 

 subgroups (not subgenera), which will intergrade and overlap to a 

 certain extent. The recognition of these subgroups is solely for con- 

 venience in synoptical keys to the species, and in order to avoid error 

 in the use of these keys, allowance must be made for a possible differ- 

 ence in the point of view between the author and the student. 



Since there has been confusion existing so long in regard to the 

 priority of generic names in this group, it seems necessary to present 

 the entire case in order to clear it up : 



Delphax was first used by Fabricius in 1798,^ with a brief description 

 as follows: 



Os labio brevi conico. Antennee compressse, raarginatae, inoscularum cantho 

 inferiore insertae. 



This characterization could not include the species of the group 

 with which we are dealing now, because of the form of the antennae. 

 The only two species mentioned under Delphax in this original descrip- 

 tion were D. crassicornis and D. clavicornis, in the order named, 

 neither of which is congeneric with the species under our considera- 

 tion. It is evident, therefore, that Delphax must be restricted to 

 crassicornis and its cogenors, and can not be used for the present 

 group of species, as has been most persistently done by several stu- 

 dents. Spinola, in 1839, used this same species, D. crassicornis 

 Fabricius, as the type for a new genus, Araeopus. This, of course, 

 was impossible, and the latter must become a synonym of Delphax. 

 Further reference is made to this under Araeopus. 



In 1866 Stal ^ further complicated matters by restricting the name 

 Delphax to D. clavicornis, which he erroneously supposed to be the 

 type, and erected a new genus, Lihurnia, for a number of species more 

 or less related to the generic group in hand. Strangely enough, Stal 

 used as the type of his genus Lihurnia a species which in 1853 ^ he 



J Supplementum Ent. Systematicae, p. 522. 

 2Heniipt. Africana, vol. 4, p. 178. 



31 have not seen this original description. St&l treats the matter, however, in Hemiptera .\fricana, 

 vol. 4, p. 179. 



