HOW INSECTS WALK AND FLY. 



17 



as), resting on the oesophagus, and two others situated each 

 side of the crop, low down. Each of the two posterior 

 ganglia is supplied by a nerve from the anterior ganglion. 

 Two nerves pass under the crop connecting the posterior 

 ganglia, and from each posterior ganglion a nerve is sent 

 backward to the end of the proventriculus. A pair of 

 nerves pass under the oesophagus from each side of the 

 anterior sympathetic ganglion, and another pair pass down- 

 ward to a round white body, whose nature is unknown 

 (Fig. 8, u). 



How Insects Walk and Fly. In walking, the locust, 

 beetle, or, in fact, any insect, 

 raises and puts down its six legs 

 alternately, as may be seen by 

 observing the movements of a 

 beetle (Fig. 11). As Carlet 

 states, an insect's legs move 

 according to the following 

 formula: 



With the claws on their fore 

 legs they pull themselves for- 

 ward; the middle legs seem to 

 support and steady the body, 

 also pushing it somewhat; while 

 the hind legs in many beetles 

 push the body forward.* 

 While the structure of the limb 

 of a vertebrate and insect is not 

 homologous, yet the mechanism 

 or functions of the parts are in 

 the main the same as indicated 

 in Figs. 12 to 15. 



The footprints of insects are 



IOJ 



FIG. 12. Section of the fore leg of a 

 Stag beetle, showing the muscles. 

 S, extensor, B, flexor, of the leg; s, 

 extensor, 6, flexor, of the femur; 

 o. femur; u, tibia; /, tarsus; fc, 

 claw; 109,, s, extensor, 6, flexor, of 

 the femoro-tibial joint, both en- 

 larged. After Graber. 



2 



See Miall and Denny's " The Cockroach." 



