10 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



marginal limules are much larger than they are in the summer form. 

 The black inner or abdominal border of the hind wings is very 

 broad. 



If we compare specimens of this form with a series of yellow 

 swallowtails from Newfoundland we find that we can not distin- 

 guish one group from the other. The form of Pa'pilio glmi^cus 

 that is found from Alaska and British Columbia to Newfound- 

 land is single brooded and is recognized as a distinct subspecies 

 under tlie name of PaflUo c/laucus canadensis. As early-spring 

 individuals taken in the District of Columbia are indistinguishable 

 from true P. g. canadensis (sometimes called arcticus), we must 

 admit that this form is not strictly speaking a geographical race or 

 subspecies, but simply a varietal form which represents the species 

 throughout the area in which there is only a single brood a year, 

 southward occurring as a progressively earlier and shorter lived 

 spring form as far as the mountains of North Carolina, toward the 

 southern limit of its range, as about Washington, being of irregular 

 occurrence and not appearing every year. 



In the vicinity of Washington only males of P. g. canodensis occur, 

 so far as is known. Female yellow swallowtails are not to be found 

 until the succeeding form appears. However, the fact that no females 

 of P. g. canadensis have been caught or noticed does not prove that 

 they do not exist, for in this form, in contrast to the other two forms, 

 the sexes are practically indistinguishable on the wing. 



Judging from the proportions of the sexes seen in collections, the 

 males in Canada seem to outnumber the females about 40 to 1, though 

 this may be due to the ease with which the males may be decoyed or 

 baited. 



A curious thing about P. g. camadensis as it is found in Washington 

 is that it is fond of gathering on mud which the males of the late- 

 spring type seem not to do. 



The late-spring form is very close to the summer form, from which 

 it differs in the direction of the early-spring form. It differs most 

 obviously from the summer form in the slightly smaller size, the 

 larger size of the yellow spots in the black borders of the fore and 

 hind wings (and in the corresponding positions on the wings of the 

 black females), and in the somewhat narrower dark border of the 

 hind wings, especially below. There are two kinds of females, one 

 yellow and one black. The males outnumber the females about three 

 to one, and in life are easily distinguishable by their more erratic 

 flight. This form is matched by summer individuals from southern 

 New York. 



In the summer form the black border on the fore wings is widest 

 posteriorly, and the included yellow spots are very small, the lower 

 ones being commonly obsolete; beneath they are entirely separated 



