BUTTERFLIES OP THE DISTRICT OF COLUMBIA 135 



doubtedly caught in ascending currents of air and swept upward 

 to the treetops, where they escaped into the eddy just above the 

 trees from which tliey were unable to escape because of the strong 

 upward drafts on every side. 



/Seasons. — The tailed blue first appears at the end of the first week 

 of April, and in a few days becomes common. It remains abundant 

 until toward the middle of May, when its numbers begin rapidly 

 to decline. Fresh individuals appear early in June, and it is soon 

 again abundant. In the latter part of June the numbers fall off, 

 but fresh specimens are seen about the first of July, and by the end 

 of the first week in that month the butterfly is once more abundant. 

 The fourth brood, in which the individuals are most numerous, ap- 

 pears toward the middle of August and flies in abundance until about 

 the end of the first week in September, the numbers then declining. 

 Individuals continue to emerge, however, until after the middle of 

 September, and the butterfly is found in small numbers until the end 

 of the season. 



Notes. — When compared with specimens from the vicinity of Bos- 

 ton males from the District are seen to be bluer with a narrower dark 

 border. Females from the District are dark brown almost always 

 heavily dusted with violet-blue scales, which on the fore wings 

 occupy a rounded triangular area extending from the base to the 

 outer end of the cell and to the lower angle, and on the hind wings 

 cover more or less completely the inner half. Rarely females from 

 the District are plain brown, as are all the females which I have 

 seen from the vicinity of Boston. In both sexes the color of the 

 underside is slightly lighter and more uniform in local individuals 

 than in those from Boston. These differences, as between southern 

 and northern examples, were long ago noticed by Mr. Scudder. 



The length of the fore wing in 16 males at hand varies from 10 mm. 

 to 13.5 mm., averaging 12.3 mm. ; in 4 females it ranges from 11.5 mm. 

 to 14 mm., averaging 12.2 mm. In 6 males from the vicinity of 

 Boston the fore wings vary from 9.5 mm. to 14 mm. in length, aver- 

 aging 12.9 mm., while in a female the fore wings are 12.5 mm. long. 

 These last averages are practically the same as the figures given by 

 Mr. Scudder. The insect therefore is smaller about Washington 

 than it is about Boston. 



It has been noticed that in this species there is no regular inter- 

 gradation between the larger and the smaller individuals, the butter- 

 flies occurring in a larger and a smaller size. This is as true here in 

 the first as in the later broods, though the very first butterflies of 

 both sexes are always small. Individuals of both sexes with the 

 fore wings not more than 10 mm. long are always to be seen, though 

 they are less numerous than the larger. 

 66544r-32 10 



