Page:Insects - Their Ways and Means of Living.djvu/177

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that termites do. Where other explanations fail, we have always to fall back on "instinct." A true instinct is a response bred in the nervous system; and the behavior of termites, as of all other insects, is largely brought

Fç. 8 3. A fore wing of a termite, Kaloterrnes approximatus, showing the humerai suture (hs) where the wing breaks off when it is discarded

about by automatic reflexes that come into action when external and internal conditions are right for their pro- duction. The physical qualities of the nervous system that make certain reactions automatic and inevitable are inherited; they are transmitted from parent to off- spring, and bring about all those features of the animal's behavior that are repeated from generation to genera- tion and which are not to be attributed to the individual's response to environmental changes. The termites have an ancient lineage, for though no traces of their family have been round in the earlier records, there can be no doubt that the ancestors of the termites were closely related to those of the roaches; and the roach family, as we have seen in Chapter III, may be reckoned among the very oldest of winged insects. In human society it means a great deal to belong to an "old family," at least to the members of that family; but in biology generally it is the newer forms, the upstarts of more recent times, that attain the highest degree of organizatlon; and most of the social insects--the ants, the bees, and the wasps--belong to families of compara- tively recent origin. It is refreshing, therefore, to find

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INSECTS