Feb., 1909.] Definition of Nysson and of N. aurinotus. 443 



differential characters parallel with those separating Acanthos- 

 tethus and Hyponysson from Nysson proper. It is evident, there- 

 fore, that the latter are not independent genera. Further, being 

 based each on a single species (and mostly on a single individual) 

 and defined by a single character known to be individually, and 

 not specifically, variable and which if employed would place a 

 single species in several genera at once, the terms Synneurus, 

 Brachystegus, Acanthostethus (Spalagia) and Hyponysson must 

 be treated as names of artificial groups and cannot be used for the 

 indication of sections or subgenera in the genus Nysson but must 

 be placed "as direct synonyms of the genus. 



The case of Paranysson is not similar. The character upon 

 which it is founded, the serrate tibiae, may be different in degree 

 in different species and may not in all cases be in correlation with 

 other characters, such as the bilobed postscutellum and the 

 short submedial cell of the hind wings and may therefor fail of 

 full generic value; but, the character being specific, the name 

 Paranysson cannot be quoted as a direct synon3-m of Nysson, 

 and mav be used subgenerically. While it ma}^ remain a matter 

 of opinion whether Paranysson should be regarded as a genus 

 and while the consideration of American species alone supports 

 the view that it is a distinct genus (the species with serrate 

 tibiae from both South and North America agreeing in the bilobed 

 postscutellum and in the venation), yet the connection with 

 Nysson, through the European scalaris and militaris, as pointed 

 out bv Gerstaecker, is, it seems to me, sufficient to sustain the 

 broader view. Study of the connecting species may discover 

 a generic character in the male eighth ventral segment or in the 

 claspers. The mandibles of Paranysson are much sinuate 

 beneath, of Nysson without sinuation; both not dentate. 



If there exists any difference between a genus and a sub- 

 genus other than one of degree, this difference is surely that of the 

 nomenclature employed, the name of the genus appearing in the 

 binomial designation of the species and that of the subgenus 

 not so appearing, and no "hedging" is possible in a binomial 

 nomenclature. It is therefore to be regretted that in Mr. 

 Cresson's paper on the "genus Nysson" (Transactions of the 

 American Entomological Society, vol. ix, p. 273, March, 1882), 

 in which he indicates "subgenera," one of which is Paranysson, 

 the inconsistency should appear, on the same page, of adopting 

 Paranysson into the nomenclature of the species with serrate 

 tibiae to the exclusion from that nomenclature of the generic 

 name Nysson ; for, notwithstanding Mr. Cresson's use of the 

 words quoted above, he has thus adopted Paranysson as a genus 

 and must be so cited. Foxia (F. pacifica Ashm., CaHf.) differs 

 from Nysson in having second recurrent in third submarginal 

 cell, and in ventral segments, 4-5 each having a lateral tooth, 9 

 pygidium serrate at tip. 



