BUI'TEEFLIES OF THE DISTRICT OF COLUMBIA 123 



not visited by these butterflies. Some minutes later a butterfly, which 

 rose 5 or 6 feet away and which could not have been much frightened, 

 mounted high into the air and departed in the direction of Great 

 Falls. 



Had the insects been more numerous this might well have been the 

 beginning of a migratory flight. They acted as described for migrat- 

 ing butterflies and the fact that there were very few means simply 

 that the supply was limited. We found later that the total number 

 in the field seemed to be much reduced, and so we surmised that prob- 

 ably others had during the morning drifted away after the fashion of 

 those we saw depart. They were more restless than they had pre- 

 viously been. They wandered about more and did not remain so long 

 on the flowers. Also, their numbers had decreased considerably. 

 Most of them were now gathered into two flocks, a small one of two 

 dozen or so individuals in the northern half of the field, and a very 

 much larger one in the southern half. Both flocks were more com- 

 pact than any we had seen previously, and as many as four butter- 

 flies were often to be seen on a single goldenrod. 



From the southern flock, which occupied an area, roughlj^, 100 feet 

 long and 25 feet wide, we took 45 specimens for examination. We 

 found that they had lost most or all of the violet iridescence, which in 

 freshly emerged examples plays over the brown of the fore wings, 

 while in practically all a few scales were lacking here and there on 

 the undersurface of the fore wings, showing that they had been 

 flying about for several days. 



The restlessness of the individuals in both flocks was quite appar- 

 ent, for they frequently shifted their position by flying a few feet. 

 The increased sociability also was apparent. Whenever an individual 

 that was flying over the field alighted, we always found that it had 

 alighted near another or near several. The butterflies could not, 

 however, be decoyed by a dead individual pinned to the goldenrod, 

 although a male Papilio pMlenor was immediately attracted to and 

 took a prolonged interest in a disabled and motionless black female 

 of P. glaucus. 



In the latter part of the afternoon individuals were seen flying 

 toward one or other of the small trees scattered about the field. Ex- 

 amination of the trees, however, disclosed only a single individual 

 clinging to a leaf. But we left before the time these butterflies 

 usually retire for the night. 



On September 24, just a week after their first appearance in large 

 numbers in the fields beyond Cabin John, these butterflies were 

 noticed at various places in the city of Washington, even in the 

 business district. On the following day they were rather frequent 

 about the city, always flying in a leisurely and aimless manner at 



