INSECTS
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 live successfully in many kinds of conditions and circumstances. Most other forms of modern insects have been evolved through an adaptation to more special kinds of habitats and to particular ways of living or of feeding. Such insects we say are specialized, while those exemplified in the roach are said to be generalized. Survival, therefore, may depend either on generalization or on specialization. Generalized forms of animals have a better chance of surviving through a series of changing conditions than has an animal which is specifically adapted to one kind of life, though the latter may have an advantage as long as conditions are favorable to it.
Fig. 61. A young mayfly, a water-inhabiting creature. (One-half larger than natural size)
The roaches, therefore, have survived to present times, and will probably live 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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