Page:Popular Science Monthly Volume 17.djvu/685

Rh than that of zoölogy—the highest department of biology—while some of its divisions are to he highly recommended on account of their great economic importance. The agriculturist has to deal directly and practically with only the two highest branches of the animal kingdom, with the jointed animals known as vertebrates and arthropods. To the first of these man himself belongs, and it is now admitted that the best and most practical way to acquire a knowledge of human physiology, anatomy, and development, is by studying the comparative physiology, anatomy, and embryology of vertebrates. Also, because our domestic animals belong to this group, with many of our friends among the birds, snakes, lizards, salamanders, toads, and fishes, it deserves special study. To the second branch belong the crab-like animals, the myriad-legged forms, those which are spider-like, and true insects, which are the highest of their branch. These we meet everywhere, at every step. They are the most abundant of all organisms, their number of species exceeding that of all other animals, with all the species of plants taken together. Every terrestrial plant and animal has its insect-pests, and these in turn have insectean destroyers, which are indirectly friends to the animal or plant. With the cultivation of extensive areas, the destruction of beneficial insects, of birds and reptiles, and their forest-homes, with the introduction of new food plants, and adaptive changes in the food-habits of insects, we favor the multiplication of our native pests, while to these we have added through commerce all the foreign marauders which can be brought with imported produce, and without the enemies which retard their increase in their own countries. At least thirty species of our most objectionable insects are derived from the Old World, among which are the dreaded currant-worm, the cabbage-worm, the cabbage-fly, the Hessian fly, the wheat-midge, the bee-moth, the apple-worm, the cabbage-lice, grain-weevils, the house-fly, the European cockroach, carpet and clothes moths and bugs, the asparagus-beetle, and the clover beetle. This group is commanding more and more attention by the great increase of its depredations from year to year.

For all these reasons, insects appear in near and important relations to man. On these accounts, but also because of the endless variety of wonderful and interesting habits and instincts among them, is their study especially recommended. Not only is the natural history of such creatures of practical value, but there is a peculiar fascination in its study that is highly beneficial in its influence, aside from the pleasure it affords. This is expressed by J. B. Hartwell as follows: "My soul is vexed, from day to day, because the writers of unrighteous fiction are so popular, while the devotees. . . of science and the promulgators of God's truths are to such a degree neglected, their writings unsought, unread. Yet not wholly so. I rejoice to believe that the number of students in the school of Nature is rapidly increasing. And I devoutly pray and hope that the beauties and