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“A plainly marked regular curve, which approaches a sinuous line, as seen in Fig. 125, is often obtained by painting many insects, for example Trichodes, Meloë, etc., which, when running, either bring the end of their hind body near to the ground or into contact with it.

Fig. 125.—Tracks of Trichodes; the middle sinuous line is made by the tip of the abdomen. Natural size.

Fig. 126.—Tracks of another insect which, in running, can only use three legs (r1, l4, r3) which become indicated differently from normal conditions. Natural size.

Fig. 127.—The same of an insect crossing over a surface inclined 30° from the horizon, whereby the placing of the feet becomes changed. Natural size.—This and Figs. 120–126 after Graber.

“The locomotive machine of insects may be called, to a certain extent, a double set of three feet each, as most insects, and particularly those provided with a broad trunk, are able to balance themselves with one of these two sets of feet, and indeed when walking, as well as when standing still, can move about even better with one set of these feet than with four legs. In the latter case, that is, if one cuts off a pair of legs from an insect, the trunk can balance itself only with extreme difficulty, and there is therefore little prospect that insects will ever become four-footed.