206 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



County, Va., beyond the Free Bridge, late in April, and I captured 

 one in the woods north of the canal 1 mile west of Cabin John, Md., 

 on April 19, 1926. There are two specimens from the District in the 

 Schonborn collection, one taken on April 21 and the other without 

 a date. 



ReTnarks. — This butterfly has a curious distribution, being found 

 in Europe in Scandinavia, Finland, and Lapland, in Asia in the 

 Altai Mouutains, and in North America in Labrador and eastern 

 Canada, and also in a slightly different form from New Jersey 

 southward to North Carolina, as well aS in the Eocky Mountains. 

 In Eurojje it extends farther northward than any other skipper, 

 passing well beyond the Arctic Circle. 



In the subarctic regions and in the mountains of Asia it flies in 

 June and July. In this vicinity it is known to fly only in the last 

 half of April, when the temperature is approximately the same 

 as at the season of its flight in Labrador and in northwestern Europe. 



What is the reason for the existence of this insect from New Jer- 

 sey to North Carolina in a colony widely separated from any other 

 area where it is to be found? Is it possible that the butterfly has 

 persisted in this area since the last southward extension of the ice 

 while to the northward it has died out as far as Quebec ? 



PYRGUS TESSELLATUS TESSELLATUS (Scudder) 

 6BA.T DABTEB 



Plate 32, Figures 2, 3 



Occywn'ence. — Frequent in moist open fields near woods and along 

 the borders of woodland roads, and locally abundant. 



I have noted single individuals of this species in several of the 

 city parks, in the Department of Agriculture and Smithsonian In- 

 stitution grounds, about Potomac Park, and in gardens and back 

 yards throughout the city, and widely scattered individuals in the 

 open fields west of Cabin John, mostly along the borders of the 

 woods. But the only place where I have seen it in abundance is in 

 the lower portion of an extensive field not far beyond the Northwest 

 Branch at Silver Spring. A small brook bordered on each side with 

 trees and bushes runs through this hollow, and in a band about 100 

 feet in width adjoining the wooded borders of this little stream this 

 butterfly is very common. 



Hahits. — In its habitat at Silver Spring the gray darter is so 

 very local that unless one happened to stray within the narrow belt 

 along the stream where it occurs its presence would never be sus- 

 pected. 



On hot and sunny days the flight of the males is extremely swift, 

 and furthermore direct, without the erratic skipping so charac- 



