I With 1 plate.| The question of how this evolution traveled, which factors directed it along the course that led insects to their present height of organization, is of deep interest to every entomologist. Insects appeared on the earth very long ago. Beginning with the middle of the Paleozoic era—namely, the Carboniferous period—the earth's crust contains undoubted traces of insects, principally impressions of wings, and indications of insects exist even in the earlier epochs. And thus, in course of this colossal interval of time, an interval the greatness of which is beyond the limit of human understanding (be this interval 30,000.000 or 00,000.000 years, the impression on the mind will not be different), the process of evolution of the insect forms continued unabated—a process which brought them to the present stage. The tremendous development attained by insect life on earth is best shown by the following few figures. By 1907, 384,000 species of insects were described and named. An annual average of about 6,000 species is being described since then, a number which shows no tendency to diminish: on the contrary, as Europeans penetrate into tropical countries, this number is showing decided increase. Thus, all agree that the number of species of insects on the earth must be expressed by a number of at least seven figures. But, whichever the number we finally agree upon, whether that of 10,000,000 species by Biley, or the more modest figure of 2,000,000 by Sharp, one fact remains certain—namely, that the number of species of insects is at least six times that of species of all the other animals put together. And, if we recall that the number of individuals of each species of insects is on the average many times greater than that of other species of animals (excepting Protozoa), the colossal development of animal life in the form of entomons will become fully evident.