172 THE CANADIAN ENTOMOLOGIST. 



SYNOPSIS OF NOMADIN.^. 



BY CHARLES ROBERTSON, CARLINVILLE, ILLINOIS. 



This paper is intended to give the results of the study of the local 

 species. 



Unless otherwise indicated, vein a = basal nervure ; vein Vj = trans- 

 verse medial nervure ; vein ;-w = first cubital nervure ; cell IIIi4.2 = margin- 

 al cell ; cell III5 = second cubital cell ; " joint " refers to antennae ; " seg- 

 ment " refers to abdomen. 



There has been enough confusion in this group to suit the most 

 stupid of lumpers. It takes a mystagogue to identify a species from a 

 description of its ornaments. Such descriptions are regular pitfalls — 

 regular synonym-traps. The description of N. bisignata, Say, can be 

 duplicated from five different local species. Mrs. Annie Trumbull Slos- 

 son sent me specimens of the immaculate form of Gnathias ovatus, which 

 had been identified for her as AF. incerta. The former has bidentate 

 mandibles and simple coxje, while the latter has simple mandibles and 

 spined coxae, and is the female of Centrias americanus. The synonymy 

 is given in Tr. Am. Ent. Soc, 22 : 125. Here the question arises as to 

 whether the N. americana, Kby.. is the same as N. incerta or the same as 

 this immaculate form of G. ovatus. The latter is rare, and has the 

 abdomen much paler than indicated in Kirby's description of the former. 

 Then, which one of these is the immaculate variety of Say's IV. bisignata? 

 Here, also, JV. incerta is by far the more probable determination. N. 

 simplex, with simple mandibles, was identified as N. bella. On compar- 

 ing the type, I found that N. bella had bidentate mandibles. 



N. affabilis, Cr., is composite. The N. Y. specimen, on which the 

 description was evidently based, is regarded as the type. The 111. speci- 

 men is the male of N. vincta. The ornaments of the two species are al- 

 most identical. 



N.rubicunda, Oliv., { = N. torrida, Sm.) belongs to Ce?itrias. 



N. bella and inaculata belong to Gnathias. I have examined the 

 types of the former twice, and of the latter once. They resemble G. 

 cuneatus, but are quite different from the local specimens. JV. viaculata 

 is much larger and more red. At present I would not unite. them. The 

 two local species are very common and very variable. In the table I have 

 indicated the colour forms at some length. They seem to show a strong 

 tendency to divide into several species, and there may be differences in 

 the hosts which they infest. I cannot separate the males in the same way. 



