134 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



wings forward and backward, moving those on either side alter- 

 nately, for a few seconds. The females are less active than the 

 males, and their flights as a rule are shorter. 



This little butterfly is very fond of flowers, especially of the 

 flowers of small leguminous plants more or less hidden in the grass. 

 It shows a decided preference for white flowers and will rise above 

 the grass tops to the flowers of the wild carrot and of small white 

 asters. It is extremely fond of the flowers of the butterflyweed, of 

 the button-snakeroot, and of the white sweetclover {Melilotus alba). 



The males enjoy sucking the moisture from muddy spots in roads, 

 which they do singly or in little scattered companies. 



Like the common blue {Lyca£nopsis argiolus), the tailed blue 

 seems to live at peace with the rest of the insect world. It is not 

 aggressive, and nothing seems to trouble it. I have never seen one 

 caught by a crab spider or a phymatid bug or by an ant, although 

 it is the commonest butterfly in the regions where the two first are 

 most abundant. 



Dr. Charles L. Marlatt has reported an interesting case of the 

 swarming of this butterfly in the District. He says : 



About the middle of July, 1888, the writer's attention was drawn to the 

 large numbers of small butterflies, of the species above named, flitting with 

 irregular but rapid flight back and forth at a height of 25 to 30 feet from 

 the ground above some elm trees which grew alongside a large fleld of red 

 clover. Occasionally one would rest for a second or two on the upper part 

 of an elm, only to quickly resume its place in the swarming mass above. 



No easy explanation of the peculiar congregating of these butterflies pre- 

 sents itself. So far as observed, it was not a nuptial flight — no union of the 

 sexes occurred. There was no general movement in any direction, but their 

 actions seemed rather of a playful or frolicsome nature. They had evidently 

 come together from the clover-field mentioned, in which they had been breed- 

 ing abundantly. 



A threatening storm of wind and rain coming on at the time may have had 

 something to do with their collecting into swarms. 



An additional instance may be given, \\hich indicates still further a semi- 

 gregarious habit with these insects. The writer has observed them in late 

 summer covering moist patches of ground in such numbers that a single sweep 

 of a net would capture 50 or more of them. Their object in this instance was 

 evidently to suck up the moisture, the extremely dry weather having doubtless 

 gteatly reduced the supply of nectar in the clover blossoms. 



The probable explanation of the congregating of these little butter- 

 flies above the elm trees is a rather simple one. They are fond of 

 flitting about where the grass is short and sparse, and therefore 

 would tend to linger in the thin grass under the elm trees. On a 

 day such as the one described there would have been strong currents 

 of air rising from the ground around and above any objects of con- 

 siderable height, such as the elm trees. The butterflies were un- 



