WITH FURTHER HISTORIES. 167 



There is another form of dimorphism which is 

 not seasonal, but occurs in all broods alike. The 

 simplest form of this appears in the genus Poly- 

 gonia, where it affects nearly all the species. The 

 most conspicuous case is in the largest, the Violet 

 Tip (Polygonia interrogationis) [Fig. 142], where 

 the two forms were once universally considered 

 distinct species ; they differ in the brightness and 



FIG. 142. Polygonia interrogationis, nat. size (Harris.) 



variegation of the lower surface of both wings, 

 and the obscurity of the upper surface of the hind 

 wings ; but the variation affects not only almost 

 every part of the coloring, but even the very form 

 of the wings, as may be readily seen by an exami- 

 nation of the exquisite plates of Mr. Edwards' 

 " Butterflies of North America."* 



* One cannot speak in too high terms of these matchless plates. 

 The care that has been bestowed upon them reflects the highest 

 credit upon the author as well as upon those whom he employs. 



