Page:Insects - Their Ways and Means of Living.djvu/290



possible for a young mosquito, deprived of the power of flight, no live the lire of its parents and no feed after the manner of its mother. Hence, the young mosquito bas adopted its own way of living and of feeding, and this bas allowed the adult mosquitoes no perfect their specialties without inflicting a hereditary handicap on their offspring. Thus agam we see the great advantage which the species as a whole derives from the double lire of its individuals. The fly will only give another example of the same thing. "J'he specialized form of the young fly, the maggot (Fig. 7), which is adapted to the requirements of quite a different kind of lire from that of the adult fly, relieves the latter from all responsibility to its offspring. As a consequence, the adult fly bas been able to adapt its structure, during the course of evolution, to a way of living best suited to its own purposes, unhampered as it would be if its characters were to be inherited by the young, to whom they would become a great impediment, and probably a fatal" handicap. A fourth principle of metamorphosis, then, we may say, is that the species as a whole bas acquired an advmltage by a double mode of existence, which allows it to take actvantage of two environmcnts dtering its lifetime, ole suited to the ftenctions of the young, the other to the fuictions of the adult. We noted, in passing, that the young insect is free to lire its own lire and to develop structures suited to its own purposes under one proviso, which is that it must even- tually revert to the form of the adult of its species. At the period of transformation, the particular characters of the young must be discarded, and those of the adult must be developed. Insects such as the grasshoppers, the katydids, the roaches, the dragonflies, the aphids, and the cicadas ap- pear in the adult form when the young sheds its skin for the last rime. The change that bas produced the adult,

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