210 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



The individuals of the summer brood of our local species have been 

 found only in the open fields, whereas those of the spring brood are 

 most abundant in the woods. 



All are active and alert, but the different species show considerable 

 .variation in their habits. In all ours the males are on the wing a 

 week or 10 days before the first appearance of the females. 



These butterflies are very fond of flowers, especially those of the 

 blueberries, wintercress {Barharea vulgaris)^ blackberries, certain 

 violets, and the Jersey-tea {Geanothus amiericanus) . In summer they 

 are very partial to the flowers of the red clover. 



In feeding they either hold the wings horizontally extended with 

 the fore wings drawn well back, or the wings are slightly raised, 

 making an obtuse or a right angle with each other. When resting 

 on the ground they sit with the wings half raised, or fully spread out 

 with the tips touching the ground. They are sometimes to be seen 

 resting on a stem of a plant with the wings drawn down so as to 

 embrace the stem and the fore wings drawn far back much after the 

 fashion of a noctuid moth. 



A curious feature of the butterflies of this genus is that the pat- 

 tern of the fore wings on the two sides of the body is never quite 

 the same, though the differences usually are slight. These are the 

 only North American butterflies in which the wings of the two sides 

 are not alike, or practically alike. 



THANAOS ICELUS (Scudder and Burgess) 



Plate 52, Figures 4 to 6 



OcGurrerwe. — Common along roadsides in woods, about exposed 

 rocks and cliffs, and along roadsides through open fields, especially 

 west of Cabin John, Md. 



Mr. Shoemaker has found it in the District early in spring. There 

 are four specimens from the District in the Schonborn collection, and 

 I have it from near Great Falls, April 19, 1925, from the fields west 

 of Cabin John, where it is common, May 11, 1930, May 12, 1929, and 

 June 2, 1929, and from fields at Beltsville, May 30, 1929. It reaches 

 its greatest abundance in the last half of May, about two weeks later 

 than T. jiwenalis. 



Reinarks. — This is the least active of the local species of the genus 

 and the easiest to catch. It has a highly irregular flight, and keeps 

 always near the ground. On the wing it greatly resembles Pholisora 

 Catullus with which it flies, though it is easily distinguished by its 

 lighter color, somewhat larger size, and the longer straight dashes in 

 its angular and highly irregular flight. 



This species has only a single brood a year, flying early in spring. 

 The caterpillar feeds on a number of different plants, but especially 

 on willow and poplar. 



