BUTTERFLIES OF THE DISTRICT OP COLUMBIA 9 



individuals of quite a different type. Both of these types are given 

 forth by chrysalids — or in the case of yellow clover butterfly arise 

 from caterpillars — that have overwintered. 



In most cases the number of individuals of the early type is very 

 small and they fly for only a short time, though the late spring 

 form is common and is on the wing for several weeks. In some years, 

 indeed, the early-spring form of the blue and yellow swallowtails 

 seems to be wholly absent. On the other hand, in the case of the 

 zebra swallowtail the early-spring form is much commoner than the 

 later, while in the case of the common blue the early form is very 

 common and flies for a long time, while the late-spring type is 

 rather rare. 



The two spring forms are generally quite different in their mark- 

 ings. In the case of the common blue, the checkered white, and the 

 zebra swallowtail they were formerly regarded as quite different 

 species, and in the case of the blue and yellow swallowtails they are 

 still regarded as distinct subspecies. 



The two spring forms differ not only in their color, but also 

 more or less in habits. The early-spring form of the checkered 

 white flies with the fairly direct and tremulous flight of the orange 

 tip {Anthocharis gemdla), while the late-spring form flies much 

 more like the cabbage butterfly. The early-spring form of all the 

 swallowtails is more restless and has a more nervous flight with more 

 constant and more rapid wing beats than the late-spring form. 

 The early-spring form of the pearl crescent and of the checkered 

 and the cabbage whites keeps close to the borders of the woods, while 

 the late-spring form, like the summer form, prefers the open fields. 

 The early-spring form of the common blue, and of the blue, yellow, 

 and zebra swallowtails, keeps wholly to the woods, though the 

 late-spring form, especially of the swallowtails, is seen in open 

 places as well as in the woods, and the summer form ranges more 

 or less extensively over open country. 



From the eggs laid by both these types develop butterflies of a 

 third type, not so very different from the late-spring type, which 

 is first seen in late June or July and flies throughout the summer. 



If we study the characters of the three seasonal types in any of 

 these species in detail some very interesting facts appear. In the 

 yellow swallowtail {Papilio glaucus) the early-spring type is very 

 small. Tlie body is very hairy, and the front of the head bears a 

 conspicuous tuft of long hairs. The dark border on the fore wings 

 is widest at the apex and tapers posteriorly; the inclosed yellow 

 spots are large, and on the under surface are fused into a long band 

 tapering posteriorly. The dark border on the hind wings is very 

 narrow; beneath it is strongly suffused with light scales and is sep- 

 arated from the yellow area by a regular line. The yellow sub- 



