“Every one knows that the oar-blades of swimming beetles always go up and down simultaneously and in regular time. On the other hand, as soon as one puts a Dyticus on the dry land, _i.e._ on an unyielding medium, it uses its hind legs entirely after the manner of other land insects; that is, they are drawn in and extended again _alternately_, as takes place clearly enough from the footsteps in Fig. 119, _A_. We learn from this that water insects have not yet, from want of practice, forgotten the mode of walking of land insects. “The forcing up of the water as a propelling power is added to the repulsion produced by the strong strokes of the oars. If the beetle stood up horizontally in the water, he would be lifted up. “As the trunk, however, assumes an oblique position when the insect wishes to swim, one can then imagine the driving up of the water as being divided into two forces, one of which drives the body forward in a horizontal direction, while the other, that is, the vertical component, is supplied by the moving of the oars. The swimming insect is thus, as it were, a snake flying in the water. “The long streamer-like hind legs of many water-bugs, for example Notonecta, approach more nearly our artificial oars. These legs are turned out from the bottom. “There is no doubt but that the legs of insects, as regards the many-sidedness and exactitude of their locomotive actions, place the similar contrivances of other animals far in the shade. We shall be forced to admire these ingenious levers still more, however, when we take into consideration their energy and strength. That the force with which the locomotive muscles of insects is drawn together is enormous compared with that of vertebrates, we may learn if we try to subdue the rhythmical movements of the thorax of a large butterfly by the pressure of our finger or to open against the insect’s will the closed jumping leg of a grasshopper, or the fossorial shovel of a mole-cricket.” LITERATURE ON LEGS AND FEET =MacLeay, W. S.= On the structure of the tarsus in the tetramerous Coleoptera of the French entomologists. (Trans. Linn. Soc. London, xv, 1825, pp. 63–73.) =Speyer, O.= Untersuchung der Beine der Schmetterlinge. (Isis, 1843, pp. 161–207, 243–264.) =Pokorsky Joravko, A. von.= Quelques remarques sur le dernier article du tarse des Hyménoptères. (Bull. Soc. imp. Natur. Moscou, 1844, xvii, pp. 140–159. Ref. in Isis, 1848, v, p. 347.) =Rossmassler, E. A.= Das Bein der Insekten. (Aus der Heimath, 1860, 3 kap., pp. 327–334, Fig.) =West, Tuffen.= The foot of the fly; its structure and action; elucidated by comparison with the feet of other insects, etc. Part I. (Trans. Linn. Soc. London, xxiii, 1861, pp. 393–421, 1 Pl.)