MECHANICS OF WALKING 



109 



"For an examination of the gait of insects, we choose, for obvious reasons, 

 those which have very long legs and which at the same time are slow walkers. 



" Insects may be called ' double-three-footed,' from the manner in which they 

 alternately place their legs. There are always three legs set in motion at the 

 same time, or nearly so, while in the meantime the remaining legs support the 

 body, after which they change places. 



"To be more exact, it is usually thus: At first (Fig. 118) the left fore leg 

 (1) steps out, then follows the right middle leg (Rz), and the left hind leg (3). 

 Then while the left fore leg 

 begins to 1'etract and thus 

 make the backward move- 

 ment, the right fore leg is 

 extended, whereupon the 

 left middle leg and the right 



o 



00 



It 



hind leg are raised in the 

 same order as the first three 

 feet." 







P" rxl 



-r 





FIG. 123. FIG. 124. 



FIG. 122. The same by the left fore (lj), middle (1 2 ), and hind, leg (/ 3 ) of a Carabus. Natural 

 size. 



FIG. 123. Tracks of a Slap* mortinaga marked by the differently painted tibial points: 

 0, tracks of fore, O, middle, /, hind leg. Natural size. 



FIG. 124. Tracks of Necrophorus vespilio. Natural size. 



Graber 1 painted the feet of beetles and let them run over paper, and goes on 

 to say : 



" Let us first pursue the tracks of the Blaps, for example (Fig. 123). Let the 

 insect begin its motion. The left fore leg stands at a, the right middle leg at 0, 

 and the left hind leg at c. The corresponding number of the other set of three 

 feet at a, 6, 7. At the first step the three feet first mentioned advance to a'B'c 1 , 

 the second set on the other hand to a'b'y'- Thereby the tracks made by the 

 successive steps fall quite, or almost quite, on each other, as appear also in the 

 tracks of a burying beetle (Fig. 124). 



"As the fore legs are directed forward and the hind legs backward, while 

 the middle legs are placed obliquely, the reason of the more marked impressions 

 of the latter is evident. 



" The highest testimony to the precise exactitude and accuracy of the walking 

 mechanism of insects is furnished by the fact that in most insects, and par- 

 ticularly in those most fleet of foot, which, whether they are running away 

 or chasing their prey, must be able to rely entirely upon their means of loco- 

 motion ; the fact, we say, that whether they desire to move slowly or more 



1 Carlet and also De Moor (1890) confirm Graber's statement that in beetles the 

 first and last appendages on the same side are in contact with the ground, while 

 the middle one is raised. On the other side of the body the middle appendage is on 

 the ground and the first and last one raised. 



