BUTTERFLIES OF THE DISTEICT OF COLUMBIA 27 



THE OCCURRENCE OF BUTTERFLIES IN THE DISTRICT OF 



COLUMBIA 



The butterflies of the District are to be seen in the greatest diversity 

 and profusion late in summer. The locality where they may be 

 observed to best advantage is the long meadow between the Conduit 

 Koad and the canal, 2 miles west of Cabin John, Md. 



Here in the second week in September the thistles are in full 

 bloom and the joe-pye-weed, the boneset, the goldenrods, and certain 

 small asters and leguminous plants are flowering profusely. In 

 these fields the pink gerardia {Agalinis purpurea) is exceedingly 

 abundant, and its lovely flowers impart a hazy flush of pink to the 

 lower herbage over extensive areas. 



Most conspicuous of the butterflies in this area is the blue swallow- 

 tail {Papilio philenor) , which is visible on every side, dashing from 

 side to side and up and down and often doubling on its course with 

 its characteristic wild impetuous flight. Less numerous, but still 

 common, is the parsnip swallowtail {Papilio polyxenes). This has 

 a less impetuous and less irregular, though nervously active, flight, 

 but on flowers it is wary and suspicious and more difficult to capture 

 than the other. About as numerous as the parsnip swallowtail is the 

 spice-bush swallowtail {Papilio troilus)^ which is at once distin- 

 guished from the others by the less hurried flight and the somewhat 

 slower motion of the wings. It flies at about the height of the 

 majority of the thistle flowers — that is, about 5 feet above the 

 ground — higher than the parsnip swallowtail and lower than the 

 upward, though higher than the downward, dashes of the blue. 

 From time to time, straying from the woods adjacent, the yellow 

 swallowtail appears, its leisurely deportment and deliberate flight 

 contrasting sharply with the actions of the other species. 



Early in the morning these swallowtails may be seen sunning them- 

 selves on the leaves of bushes or on grass blades. They soon begin to 

 course about, dotting the fields on every side. After the middle of 

 the morning their exertions begin to tell on them, and in increasing 

 numbers they begin to feed upon the thistle flowers. Early in the 

 afternoon they are mainly occupied in feeding, flying from one flower 

 to another. After the middle of the afternoon their numbers grad- 

 ually decrease, each kind returning to its proper habitat, the parsnip 

 to the grassy fields, the others to the woods. 



After the swallowtails the most conspicuous butterfly on the thistle 

 flowers is the milkweed butterfly, or monarch {Daiiaus plexippus)^ 

 of which several are to be seen at any time of day. These feed from 

 early morning to late afternoon, and, when resting on the flowers 

 with the wings closed above the back, are singularly unsuspicious and 

 with due caution may be captured with the fingers. 



