Page:Phylogeny of cynipid genera and biological characteristics.pdf/4



The first abscissa of the radial vein of the wings of the Cynipidæ varies from an arcuate to a sharply angulate condition, some species showing a pronounced, vein-like projection into the radial cell at the apex of the angle made by the vein. Every degree of gradation between the extreme forms may be found. Indeed, so remarkably complete is the list of transitional forms that it was this exhibition which first drew my attention to the existence of evidence of the course of evolution in the group, and I have failed to find any other one line of data which offers as complete a story as that presented by these gradations in vein form. A sufficient display of this variation is shown in the wings of the forty-five species which I figure to remove any necessity for an account of the details of conditions in particular species.

It is to be remarked that no great variation in the vein is to be found among the species of a single genus, i. e., the form of the vein is a generic character, indicating the same lines of generic limits which were drawn originally after considerations of very diverse morphological characters. In the Figitidae, in Aulacidea, Aylax, Neuroterus, Disholcaspis, Cynips (of European authors), and in Apmhibolips every species which I have seen agrees in details of venation with a pattern typical for its genus.