BUTTERFLIES OF THE DISTRICT OF COLUMBIA 117 



observed flying over the sea far out of sight of land, and has been 

 reported hundreds of miles at sea over the Atlantic. In crossing 

 Massachusetts Bay from Boston to Provincetown late in summer in 

 almost any year, one will see one of these butterflies every few miles, 

 and sometimes one or more will be in sight for almost the entire 

 distance. They are seen to be flying — always in a straight line — in 

 any direction, though usually north, apparently because most of 

 them come from Cape Cod, in marked contrast to the local pierids 

 {Colias philodice and Pieris rapae)^ which when over the sea always 

 fly against the wind. 



On the south shore at Scituate, Mass., milkweed butterflies from 

 time to time are seen coming in from the sea flying at a height of 

 300 or 400 feet, almost out of sight (Hugh Upham Clark). As soon 

 as they are over the land they suddenly descend, almost as rapidly 

 as if they dropped, to within a few feet of the ground. 



Over water the flight is higher, more rapid, and more direct than 

 it is over the land. The altitude is usually between 10 and 15 feet 

 above the surface of the water, though sometimes much higher. The 

 wings are moved continuously and rather rapidly, and there is no 

 seesawing motion. The speed is usually between 20 and 25 miles 

 an hour. Over water the insect is concerned only with covering all 

 the distance possible, whereas over the land it is mainly concerned 

 with surveying the ground beneath it. In long flights over water 

 it gradually tires and sinks nearer and nearer the surface, so that 

 well out to sea it is always seen flying very low. 



Early in spring most of the butterflies that have come out of 

 hibernation fly very low, within 4 to 6 inches of the ground or the 

 tops of the dead grass blades, and they are then, with their faded 

 and putty-colored wings more or less closely matching the ground 

 beneath them, very inconspicuous, easily escaping notice. 



In summer this butterfly is to be found spending the night hang- 

 ing downward from the topmost leaves or shoots of herbaceous 

 plants in the open fields, from the outer leaves of bushes or of trees, or 

 from the smaller branches of bushes or trees, often at a considerable 

 distance above the ground. It makes no effort whatever to hide itself, 

 in marked contrast to the large fritillaries [Argynnis idalm and A. 

 cybele), which early in the morning are never seen until they are on 

 the wing. 



The milkweed butterfly is a rather stupid insect and is not at all 

 shy — indeed, most individuals may with care easily be captured with 

 the fingers. It is difficult to frighten, but when thoroughly alarmed 

 it flies rapidly and straight away at about double its usual speed with 

 a continuous rapid and labored beating of its wings, graduallj'^ rising 

 as it goes. Ordinarily after reaching a height of from 10 to 20 feet 

 it ceases to rise, and slowly descends, keeping on, however, until it is 



