THE NYMPHS 



somewhat an interrogation-mark, but more nearly a semicolon. 

 On the upper side the outer margins of the wings and the tails 

 of the hind wings are tinged with violet. Expanse two and 

 one-half to three inches. 



This species is dimorphic; and the two forms differ so con- 

 stantly and in such a marked manner that they were de- 

 scribed as distinct species. In P. interrogationis interroga- 

 tionis the upper surface of the hind wings is not much darker 

 than that of the fore wings, and there is a submarginal row of 

 fulvous spots in the broad ferruginous brown border ; this 

 variety is commonly known 2&fabricii. In P. interrogationis 

 umbrosa (P. i. um-bro'sa) the outer two-thirds of the upper 

 surface of the hind wings is blackish, and the submarginal 

 fulvous spots are obliterated, except sometimes faint traces 

 near the costal margin. Many other differences are pointed 

 out by Scudder. The relation of these two forms to each 

 other was thoroughly investigated by Edwards. The dimor- 

 phism is seasonal, but not strictly so. All of the wintering 

 butterflies are fabric ii ; and from their eggs are produced 

 chiefly umbrosa; but fabricii occurs in the summer broods. 



Caterpillar. — -About one and one-half inches long. Red- 

 dish-brown in color with lighter markings of irregular dots 

 and patches. It has many branching spines, a pair of them 

 being on the top of the head. 



Food-plants. — Elm, hop, hackberry, nettle, false nettle, 

 and linden. 



It would seem at first glance that certain but- 

 terflies come to us labeled with a recognition 

 mark on the hind wings, so that we shall have no 

 trouble about identifying the species. The violet- 



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