1^4 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



usually about 8 or 10, but sometimes from 50 to 100 or more, feet 

 above the ground. 



On the succeeding day (September 26) a visit was made to the 

 Cabin John meadows. In the northern half of the main field there 

 were a few scattered butterflies feeding on the goldenrod and asters — 

 perhaps a dozen were seen in all. This is but little in excess of what 

 would be expected at this date in a normal season. Half a dozen of 

 the butterflies were caught. One was freshly emerged, and the 

 others were all fairly fresh — 2 or 3, one possibly 4, da3^s old, judged 

 from the condition of the iridescence of the fore wings. Certainly 

 none of them had been on the wing for as much as a week. 



It was rather late and the insects were getting ready to spend the 

 night. When feeding in the fields this butterfly always spends the 

 night wherever night happens to overtake it, hanging from a golden- 

 rod or aster or from an inclined sprig of some other plant. I have 

 noticed that the lower fruiting shoots of Agri7/ionim parviflora are 

 especially attractive at this season. 



There were none of these butterflies in the southern half of the 

 field, but an examination of a grove of trees south of the field dis- 

 closed two flying about among* the trees in a desultory sort of way 

 and occasionally perching on the underside of small dead limbs 8 

 or 10 feet above the ground. On the preceding day it had been 

 reported to me by Hugh U. Clark that an individual had been seen 

 in Rock Creek Park flying among the trees at a height of about 10 

 feet and perching on the lower side of branches. Some of the 

 butterflies seen about the city were observed to light on the branches 

 of trees, soon, however, resuming their aimless wandering. 



It was apparent that all the butterflies that had emerged on Sep- 

 tember 16 and 17 had left the fields, with the possible exception of 

 the two seen in the adjacent woods, though these were very likely 

 younger. So far as these fields were concerned, the unusual 

 abundance of these butterflies was a thing of the past ; the population 

 had now returned to normal. 



The butterflies seen in Washington presumably drifted into the 

 city from the surrounding country on every side, as there is no 

 reason to suppose that the increase in the normal numbers of this 

 butterfly was confined to the region about Cabin John. 



A most peculiar fact in connection with the appearance of this 

 butterfly in the meadows beyond Cabin John is that in these meadows 

 its food plant {Asclepias syriaca) is not to be found. There are a 

 few scattered plants of the red milkweed {A. incamata) and of the 

 butterflyweed (J., tuherosa)^ while the dogbane {Afocynv/tn canna- 

 hinum) is abundant; but we have never found the caterpillars on 

 any of these. Indeed, we have never found the caterpillars in the 

 District area at all. 



