94 BULLETIN 15 7, U. S, NATIONAL MUSEUM 



less completely defoliate ornamental trees, particularly willows and 

 poplars but occasionally also elms. In California they sometimes 

 defoliate rose bushes. 



It was formerly commonly supposed that these caterpillars are 

 poisonous, and so great was the fear of them that people would cut 

 down all the poplar trees about their houses to prevent their 

 appearance. 



Genus POLYGONIA Hubner 



POLYGONIA INTERROGATIONIS (Fabricina) 



Question Mark 

 Plate 10, Figure 3 



Occurrence. — Frequent, though not very common, throughout the 

 District and surrounding country. It is most numerous in the open 

 woods along the canal and Conduit Eoad from Cabin John to 

 Great Falls. 



The question mark frequents open deciduous woods, the borders 

 of woodland roads, and fields and gardens in the vicinity of woods. 



In the National Museum there is a specimen taken in Washington 

 by A. M. Ballinger on September 13, 1912, and another taken at 

 Rosslyn, Va., August 29, 1913, on elm. 



Habits. — The flight of this butterfly is rapid and irregular, but 

 when traveling over open country it flies high, from 6 to 10 feet or 

 more above the ground, in a straight line with a continuous and 

 rather slow flapping of the wings. 



The question mark especially loves to play about open places in 

 the woods and along the sides of woodland roads and the bushy or 

 wooded borders of fields, pitching down upon a leaf, opening and 

 closing its wings, darting away, and, after circling irregularly about, 

 returning almost to the spot from which it started. Like all its rela- 

 tives it is fond of basking in the sunlight with its wings outspread, 

 usually on a leaf of a convenient bush, sometimes on a log or stone. 



The females of the dark summer form have the curious habit of 

 fluttering slowly about in the dark interior of bushes or thick groups 

 of herbaceous plants after the fashion of Argynnis cyhele. 



Though it occurs everywhere with the hop merchant {Polygonia 

 comma) , it is much more often seen in open country than the latter, 

 for it sometimes wanders widely over fields and grass lands. It 

 is occasionally noticed about willow trees in meadows, and until a 

 few years ago was not infrequent about elms in the parks and along 

 the streets of Washington, particularly in the Smithsonian 

 Institution grounds. 



Its chief food plant in this region seems to be the hackberry 

 {Celtis occidentalis), and I have found its pupae on elm in the 



