64 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



It is alert and quick and rather shy, and when alarmed dashes wildly 

 off into the nearest thicket or drops into the grass. It is sometimes 

 found in the borders of fields adjacent to woods, and here it is much 

 more easily caught than in the woods themselves. Though it is most 

 active on hot and sunny days, it also flies more or less in cloudy 

 weather, or even in a light rain, and under these conditions it is less 

 wary than when the sun is shining. 



It is fond of sunning itself on a leaf or log or stone with the wings 

 closed above the back, the body at right angles to the path of the 

 sun's rays, and the wings so tilted that the sunlight falls perpendicu- 

 larly upon them. But sometimes, especially in the early morning 

 and after a rain, it will rest with its back to the sun and with the 

 wings more or less widely spread. 



In taking up a position on a sunlit leaf the butterfly drops sud- 

 denly down with the wings closed, abruptly turns itself at right 

 angles to the sun's rays, and with a jerk tilts its wings to the proi3er 

 plane. As Mr. Scudder has noticed, it has a curious jerky walk 

 somewhat like that of a wasp. 



Seaso7i. — The wood nymph first appears at the very end of May 

 and is common throughout June and most of July, fresh individuals 

 appearing quite throughout the month in diminishing numbers. 

 Early in August the numbers rapidly decrease, and by the end of the 

 first week in August it has almost completely disappeared. Occa- 

 sional individuals, however, are sometimes met with throughout 

 August and even until the end of September. 



As a rule the increase in the numbers of this species after its first 

 appearance is gradual, and the numbers diminish gradually in the 

 last half of July and with increasing rapidity in early August. The 

 individuals on the wing at any one time are therefore never very 

 numerous. Sometimes, however, as in 1930 (May 30), it appears 

 suddenly in large numbers and almost or quite disappears early in 

 July. 



The usual delayed emergence of this species is probably due to the 

 effect of hot spells in spring, the influence of which is very variable 

 according to local factors, such as proximity to cold streams and 

 bogs. In cool seasons the butterflies tend to emerge more nearly 

 simultaneously, giving the appearance of unusual abundance, later 

 disappearing simultaneously. 



Mr. Scudder says that this butterfly appears in the extreme south 

 of New England about May 20, and in the vicinity of Boston usually 

 at the close of the month or the very first of June. It remains com- 

 mon throughout June, seldom much longer, but occasional specimens 

 may be taken far into July. 



F. H. Sprague said that in eastern Massachusetts very few good 



specimens are met with after the middle of June, and by the first of 



