matter of survival of the fittest, the roach, judged by survival, must be a most fit insect. Its fitness, however, is of a general nature; it is one that adapts the roach to lire successfully in many kinds of conditions and circum- stances. Most other forms of mod-
Fie,. 6I. ,ai young mayfly, a water-inhabiting crea- rure. (One-half larger than natural size)
ern insects have been evolved through an adaptation to more special kinds of habitats and to particular ways of living or of feed- mg. Such insects we say are spccialized, while those exemplified in the roach are said to be general- ized. Survival, therefore, may de- pend either on generalization or on specialization. Generalized forms of animais have a better chance of surviving through a series of chang- ing conditions than has an animal which is specifically adapted to one kind of life, though the latter may have an advantage as long as con- ditions are favorable to it. The roaches, therefore, have sur- vived to present times, and will probably lire as long as the earth is habitable, because, when driven from one environment, they make
themselves at home in another; but we have all seen how the specialized mosquito disappears when its breeding places are destroyed. From this consideration we can draw some consolation for the human race, if we do not mind likening ourselves to roaches; for, as the roach, man is a versatile animal, capable of adapting himself to all conditions of living, and of thriving in extremes.
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