so represented in the New World by identical species. Among the arborescent plants, alders, willows, junipers, and the common yew exist in the cold or temperate regions of both worlds. While we refrain from dwelling on the grasses and ferns, the dissemination of which to great distances is one of the most common phenomena,[1] we are able to cite plants which seem hardly adapted to leap over the arms of the sea, such as orchids and lilies of northern Europe, which are also common in North America.
The numerous world of insects furnishes hundreds of examples of species that have passed across from the arctic regions of Europe into America. Of the beetles, insects generally sedentary and possessed of means of locomotion so inferior that they would hardly venture to cross a sea with them, we can mention not less than three or four hundred species as common to both continents. We are particularly struck with the number of carnivorous species (Carabides), which, living on the land and hiding under stones, are disseminated very slowly. These species of carnivorous Coleoptera may be followed from the north of the European continent to Iceland, the shores of Greenland, Labrador, and Canada,[2] It would be absurd to suppose that man has been able in his migrations to carry such a multitude of the lower creatures across the ocean. Notwithstanding the daily chances and the continual transportation of all kinds of food-products, the common chafer of Europe has not been introduced at any point in North America.
Lepidopterous insects (butterflies and moths), aided by a favorable wind, are undoubtedly sometimes carried over the sea; and it is not impossible that when they fall upon a land remote from the country of their origin they may live and propagate themselves there. These, however, are exceptional cases, while the Lepidoptera of the New World may be counted by the legion. The common vanessas of Europe abound in the northern parts of America,[3] and the argynnes of Lapland and Iceland[4] and the satyrs of the genus Chionobas live also in Labrador. The enumeration could be easily extended.
It is fair to suppose that investigations properly directed would enable us to recognize, in some American forms very close to the European, local varieties of the same species. It may
- ↑ M. O. Franchet, a botanist attached to the Museum of Natural History, has made, at my request, a complete examination of the plants of northern Europe which are diffused to a greater or less extent in North America.
- ↑ Blethera ardica, Nebria nivalis, Bembidium Grapei, Patrobus septentrionis, Pterostichus vitreus, P. arcticola, Amara erratica, A. interstitialis, A. brunnea, Platyrus Bogemanni, Miscodera arciica.
- ↑ Vanessa antiopa, V. Paolychlorus, V. Urtica, V. Atalanta.
- ↑ Argynnis Freya, A. Frigga.
