Page:Insects - Their Ways and Means of Living.djvu/37

 The egg germ begins its development as soon as the eggs are laid in the fall. In temperate or northern latitudes, however, low temperatures soon intervene and development is thereby checked until the return of warmth in the spring—or until some entomologist takes the eggs into an artificially heated laboratory. The eggs of some species of grasshoppers, if brought indoors before the advent of freezing weather and kept in a warm place, will proceed with their development, and young grasshoppers will emerge from them in about six weeks. On the other hand, the eggs of certain species, when thus created, will not hatch at all, the embryos within them math a certain stage of development and there they stop, and most of them never will resume their growth unless they are subjected to a freezing temperature! But, after a thorough chilling, the young grasshoppers will come out, even in January, if the eggs are then transferred to a warm place.

To refuse to complete its development until frozen and then warmed seems like a preposterous bit of inconsistency on the part of an insect embryo; but the embryos of many kinds of insects besides the grasshopper have this same habit from which they will not depart, and so we most conclude that it is not a whim, but a useful physiological property with which they are endowed. The special deity of nature delegated to look after living creatures knows well that Boreas sometimes oversleeps and that an egg laid in the fall, if it depended entirely on warmth for its development, might hatch that same season if mild weather should continue. And then, what chance would the poor fledgling have when a delayed winter comes upon it? None at all, of course, and the whole scheme for perpetuation of the species would be upset. But, if it is so arranged that development within the egg can reach completion only after the chilling effect of freezing weather, the emergence of the young insect will be deferred until the return of warmth in the spring, and thus the species will have a guarantee that its members will not be cut down by