Butterfly.—The principal points of difference between this and the preceding species, its closest ally, have already been pointed out, and are brought into view upon the plate.
Early Stages.—These are quite well known. The caterpillar feeds upon Ptelea, Xanthoxylon, and various species of Citrus. It is very common in the orange-groves of Florida, where the people call the caterpillar the "orange-puppy," and complain at times of the ravages perpetrated by it upon their trees. It appears to have been gradually spreading northward, and in quite recent years has appeared at points in the Northern States where before it had never been observed. It has been recently taken in Ontario. It has become rather abundant in the vicinity of the city of Pittsburgh, where no observer had seen it prior to the year 1894. It is one of the largest and most showy species of the genus found within our faunal limits.
(9) Papilio aliaska, Scudder, Plate XLI, Fig. 1, ♂ (The Alaskan Swallowtail).
Butterfly.—This interesting form of the species, known to entomologists as Papilio machaon, Linnæus, and to every English school-boy as "the Swallowtail," represents a colonization from the Asiatic mainland of this insect, which is the sole representative of the genus on English soil. It differs from the English butterfly by having more yellow on the upper side of the wings, and by having the tails of the secondaries much shorter.
Early Stages.—Undoubtedly these are very much like those of the forms found in Europe and Asia, and the caterpillar must be sought upon umbelliferous plants.
Thus far this insect has been received only from Alaska, and is still rare in collections.
(10) Papilio zolicaon, Boisduval, Plate XXXVIII, Fig. 1, ♂ (Zolicaon).
Butterfly.—This species is somewhat nearly related to the preceding, but may at once be distinguished from it by the broader black borders of the wings, the deeper black on the upper side, and the longer tails of the secondaries. The figure given in the plate is only two thirds of the natural size.
Early Stages.—These have been fully described by Edwards, and are shown to be much like those of P. asterias. The caterpillar, like that of the last-mentioned species, feeds upon the Umbelliferæ.
Zolicaon ranges southward from Vancouver's Island to Arizona, and eastward to Colorado. It is more abundant in the valleys and foot-hills than on the sierras.