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Fig. 168.—Tipula in the act of flying, showing the various attitudes of the wings and the position of the balancers.

Graber’s views as to the mechanism of the wings, flight, etc.

In the meantime, then, we may not trust to appearances. As their development indeed teaches us, the wings as well as the additional members must be regarded as actual evaginations of the common sockets of the body, and in order especially to refute the prevalent opinion that these wing-membranes are void of sensation, it should be remembered that Leydig has proved the existence, as well as one can be convinced by experiment, of a nerve-end apparatus in certain basal or radical veins of the wing-membrane, which is very extensive and complicated, and therefore indicates the performance of an important function, perhaps of a kind of balancing sense, and also that these same insect wings, with their delicate membrane, are very easily affected by different outside agents, as, for instance, warmth, currents of air, etc.