MOSQUITOES AND FLIES
are provided with sets of highly developed wing muscles which are much more effective than those of other insects. From these examples, therefore, we can not well judge of the mechanical efficiency of two pairs of equal wings moved by the equipment of muscles possessed by most
Fig. 168. Evolution of the wings of insects
A, wings of a termite, approximately the same in size and shape. B, wings of a katydid, the hind wings are the principal organs of flight. C, wings of a beetle, the fore wings changed to protective shells, elytra (El), covering the hind wings. D, wings of a hawk moth, united by the spine (f), which is held in a hook on under surface of fore wing. E, wings of the honeybee, held together by hooks (h) on edge of hind wing. F, wing of a blowfly, and the rudimentary hind wing, or halter (Hl)
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