March, 1898] GROTE : CLASSIFICATION OF I.EPIDOPTERA. 21 



may consult also my illustrated paper in the " Verhandlungen der 

 Gesellschaft Deutscher Naturforscher und Aerzte " 1896, p. 197. In a 

 linear series we would arrange the generic types thus : Altacus, Saturnia, 

 Hemileuca, Aglia, Automeris, Citheronia. 



In a foot-note, Journ. N. Y, Ent. Soc., VI, 46, I have written that the 

 crossvein becomes oblique in Aglia and Citheronia. As I recollect, I 

 had in my mind to write Eacles, but a fresh study of the latter genus, 

 and all the Citheronians now accessible to me, has led me to the con- 

 clusion that everywhere in this group the crossvein remains transverse. 

 No steps that I can now clearly recognize as such have been taken, as in 

 Aglia, towards an independence of IV2. But even were my former 

 statement correct, the argument supposed to be drawn from it is futile. 

 For the movement is secondary in its nature and would not indicate any 

 necessary nearer connection between Aglia and Citheronia. What we 

 want is primary character, underlying the general type of the wing and 

 this we have found in the long stem of IV2 and IVi in Saturnia, 

 together with the other comparative characters here discussed, as opposed 

 to the issuance of IV2 from the crossvein in A^lia, together with the 

 equally opposing features above summarized. 



We have above admitted that the peculiarly Citheronian type of the 

 Agliadffi, stands at a greater distance from Aglia and Automeris than 

 these two from each other. It remains here to point out these differ- 

 ences and emphasize the conformity to a common type of wing. The 

 wing in the Citheronians has pursued a slightly varying form of special" 

 ization of the Media from the other groups of Emperor Moths, one that 

 we meet on occasion again in the Day- Butterflies and also the Hawk 

 Moths. How far this variation is caused by the mechanics of the wing, 

 I cannot now enter upon. Vein IVi travels up the lower edge of the 

 Radius, and the extent of its absorption by the Radius is the measure of 

 the specialization of the genera. These stand, in ascending order, 

 Eacles, Citheronia, Anisota. I do not know the neuration of Sphingi- 

 campa, nor whether it bears out my formerly expressed idea that it stood 

 nearer to Eacles than to Citheronia. It is probably a specialized form. 

 But although the wings of Citheronians are on the whole perhaps more 

 specialized, as compared with Automeris, and in a different way, we 

 have more than a reminder of the Aglian and Automerid pattern. The 

 Radius is four-branched, and this is the natural precusory stage of the 

 three-branched, here the Aglian and Automerid, wing. In Anisota vein 

 III i +2 has traveled up the Radius and is given off beyond the cell. In 

 the median system vein IV2 inclines to the Radius, and vein IV3 



