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CLOUDED SULPHUR
Most of the butterflies of the United States show a relationship to those of the lands south of us. As the ice at the end of the Glacial Period retreated there was an invasion of forms from the south. The Monarch, one of our very commonest species, makes an annual migration into the northern parts of the continent, coming up from the south, as the milkweeds begin to sprout and put forth leaves, and then in autumn retreats again to “lands of sun.” The species goes far north into Canada, and in the fall of the year huge swarms of the retiring insects may be seen clustering upon trees on the northern shores of the Great Lakes, and also about Cape May in New Jersey. Many, no doubt, are drowned in the lakes and in the ocean as they try to make their way farther south.
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COMMON WOOD-NYMPH
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EYED EMPEROR
Among the most conspicuous and beautiful butterflies of the United States are the Swallowtails, which belong to the genus Papilio. We have many species. There are only three found in all Europe. One of these (Papilio machaon), now nearly extinct in England, surviving only in the fens of Cambridge and Norfolk, has many first cousins in North America, one of which (Papilio zelicaon) is represented on the plate entitled “A Group of Swallowtails.” The metropolis of the Machaon group of Swallowtails is North America, and species belonging to it are found from Newfoundland to Central America. I have a strong suspicion that the butterflies of this group originated in the New World, as did the horse, the camel, and many other animals, and that at a time when North America and Asia were connected with each other in the region of Bering Sea, as we know they were, this insect “went west” and finally established a colony in England, which was at about that time also hitched fast to the continent of Europe.