INSECTS
defense. A pair of slender tubes, the cornicles, projecting from the rear end of the body, eject a sticky liquid which the aphids are said to smear on the faces of attacking insects; but the ruse at best probably does not give much protection. Parthenogenesis and large families are the principal policies by which the aphids insure their race against extinction.
The presence of "evil" in the world has always been a thorn for those who would preserve their faith in the idea of beneficence in nature. The irritation, however, is not
Fig. 103. The aphis-lion, feeding on an aphis held in its jaws
in the flesh but in a distorted growth of the mind, and consequently may be alleviated by a change of mental attitude. The thorn itself, however, is real and can not be explained away. Beneficence is not a part of the scheme by which plants and animals have attained through evolution their present conditions and relations. On the other hand, there are not good species and bad species; for every creature, including ourselves, is a thorn to some other, since each attacks a weaker that may contribute to its existence. There are many insects that destroy the aphids, but these are "enemies" of the aphids only in the sense that we are enemies of chickens and of cabbages, or of any other thing we kill for food or other purposes.
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