32 THE CLASS OF INSECTS. 



to the hinder edge ; there are also sets of dorsal and ventral 

 muscles going in an oblique or vertical course. The muscles 

 are either colorless and transparent, or yellowish white ; and 

 of a soft, almost gelatinous consistence. In form they are 

 simply flat and thin, straight, band-like, or pyramidal, barrel 

 or feather-shaped. They act variously as rotators, elevators, 

 depressors, retractors, protrusors, flexors, and extensors. 



The muscular power of insects is enormous. The Flea will 

 leap two hundred times its own height. Certain beetles can 

 support enormous weights. Newport cites the case of Geo- 

 trupes stercorarius which is "able to sustain and escape from 

 beneath a pressure of from twenty to thirty ounces, a prodi- 

 gious weight when it is remembered that the insect itself does 

 not weigh even so many grains." Some beetles have been 

 known to gnaw through lead-pipes, and the Stag-beetle of 

 Europe, Lucanus cervus, has, as stated by Mr. Stephens, 

 gnawed "a hole an inch in diameter through the side of an 

 iron canister in which it was confined." 



u The motions of the insect in walking as in flying are 

 dependent, in the perfect individual, entirely upon the thoracic 

 segments, but in the larva chiefly upon the abdominal. Al- 

 though the number of legs in the former is always six, and in 

 the latter sometimes so many as twenty-two, progression is 

 simple and easy. Muller states (Elements of Physiology, p. 

 970, Translation) that on watching insects that move slowly 

 he has distinctly perceived that three legs are always moved at 

 one time, being advanced and put to the ground while the 

 other three propel the body forwards. In perfect insects, those 

 moved simultaneously are the fore and hind feet on one side, 

 and the intermediate foot on the opposite ; and afterwards the 

 fore and hind feet on that side, and the middle one on the 

 other, so that, he remarks, in two steps the whole of the legs 

 are in motion. A similar uniformity of motion takes place 

 in the larva, although the whole anterior part of the body is 

 elevated and carried forwards at regular distances, the steps of 

 the insect being almost entirely performed by the 'false,' or 

 abdominal legs." 



"Inflight the motions depend upon the meso- and meta- 

 thoracic segments conjointly, or entirely upon the former. The 



