LOCOMOTION OF INSECTS. 301 



(784.) In Cimbex lutea (fig. 150, D) the arrangement of the suckers 

 is different, one large and spoon-shaped disk being attached to the 

 extremity of each tarsal joint. Moreover, in this case there is another 

 singular structure : two spur-like organs project from each side of the 

 extremity of the tibia, each being provided with a sucking disk, while 

 the two together form a strong prehensile forceps. 



(785.) In some Water-beetles (Dytiscidce) the feet are armed with a 

 still more elaborately constructed apparatus of suckers ; but in this case, 

 as they are only met with in the male insect, they perhaps ought rather 

 to be looked upon as a provision made for the purpose of securely hold- 

 ing the female during sexual union, than as being specially connected 

 with locomotion. 



(786.) In the anterior legs of the male Dytiscus the first three joints 

 of the tarsus are excessively dilated, so as to form a broad circular 

 palette: on examining the inferior surface of this expanded portion 

 under a microscope, it is seen to be covered with an immense number of 

 sucking-cups (fig. 150, r), two or three being much larger than the rest ; 

 but they form collectively a wonderful instrument of adhesion. 



(787.) The middle pair of legs of the same beetle (fig. 150, A) exhibit 

 a somewhat similar structure ; but in this case the disk upon which 

 the sucking apparatus is placed is much elongated, and the suckers are 

 all of small dimensions. 



(788.) In the female Dytiscus (fig. 152, c) this configuration of the 

 tarsus is wanting ; and moreover the surface of the back is marked with 

 deep longitudinal grooves that do not exist in the male insect, but seem 

 to be an additional provision for facilitating the intercourse of the sexes 

 in these powerful aquatic beetles. 



(789.) Another mode of progression common among insects is by 

 leaping, to which, from their extraordinary muscular power, these little 

 beings are admirably adapted. The common Flea, for example (Pulex 

 irritans) (fig. 153), will leap two hundred times its own length ; and 

 many Orthoptera possess a power of vaulting through the air scarcely 

 less wonderful, of which the Cricket affords a familiar instance. In such 

 insects (fig. 145, A, B) the thighs of the posterior legs are enormously 

 dilated, and the length of these limbs is much greater than that of the 

 anterior pair. When disposed to leap, such insects bend each hind-leg, 

 so as to bring the tibia into close contact with the thigh, which has 

 often a longitudinal farrow, armed on each side with a row of spines, to 

 receive it. The leg being thus bent, they suddenly unbend it with a 

 jerk, when, pushing against the plane of position, they spring into the 

 air*. In many of these saltatorial tribes the tarsus is furnished with 

 very curious appendages, either provided for the purpose of obviating 

 any jar when the animal alights from its lofty leaps f, or else they may 

 * Kirby and Spence, Introduction to Entomology. 4 vols. 8vo. 

 f Sir E. Home, Phil. Trans. 1816. 



