HEADLEE] A STUDY IN BUTTERFLY WING-VENATION 287 
My own studies have convinced me that this primitive type of 
radius prevails among the most generalized lepidoptera such as 
Hepialus, Sthenopis, and Castnia cochrus. Spuler also evidently 
considered this type the most primitive in the Lepidoptera, for he 
figured this exact condition in his “ Schema des Vorderfliigelgeaders 
der Schmetterlinge ”* (pl. Lx, figs. 1-5 and Ir). 
This, then, being the prevailing condition of radius not only in the 
most generalized lepidopterous wings but also in generalized insect 
3d As 
Fic. 35.—Hypothetical type of primitive rhopalocerous fore wing. 
wings generally, as was shown by Comstock and Needham, may 
safely be laid down as the primitive lepidopterous radius from which 
the present types have been developed. Usually the modifications 
take the form of a coalescence between the radial branches, or of a 
more or less complete atrophy of individual branches. In fact, 
these are the means by which the heterocerous radius has been modi- 
fied. The rhopalocerous radius, on the other hand, shows not only 
the effects of such modifications but of a splitting back of R,,, until 
it finally comes to arise near the base of the main stem of radius 
(text fig. 35). The traces of the last appear in the adult wing of 
Anosia plexippus in the form of two spurs and a connecting line. 
One of the spurs is very short and projects from the base of radius 
into the discal cell and toward the outer edge of the wing, the other 
projects from the base of M, into the discal cell and toward the base 
of the wing, while the line connects the two spurs (plate fig. 12). 
Although these traces are of themselves suggestive, they are not con- 
vincing proof of such a modification of radius. The tracheation of 
the pupal wing, however, clearly explains and supplements the evi- 
dence furnished by these remnants. Trachea R,,, is found to follow 
*A. Spuler, Zur Phylogenie und Ontogenie des Fliigelgeaders der Schmet- 
terlinge, Zeitschr. wiss. Zool., L111, 4, 1802, pp. 597-040. 
