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 Paranvsson 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 
Paranvsson cannot be quoted as a direct synonym of Nysson, 
and may be used subgenericallv. While it may remain a matter 
of opinion whether Paranvsson 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 
Nvsson, through the European scalaris and militaris, as pointed 
out by 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 Paranvsson 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 Paranvsson, 
the inconsistency should appear, on the same page, of adopting 
Paranvsson 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 Paranvsson as a genus 
and must be so cited. Foxia (F. pacifica Ashm., Calif.) differs 
from Nysson in having second recurrent in third submarginal 
cell, and in ventral segments, 4-5 each having a lateral tooth, $ 
pygidium serrate at tip. 
