MUSCULAR POWER OF INSECTS 



219 



The leaping force of locusts was found by Straus-Durckheim to be 

 in (Eclipoda yrossa as 1.6, in CE. parallela as 3.3 of their weight. 



FKJ. 23S. Tfxpa crabro, fixed and stained as in the subjects of the other figures. /, -BT, P 

 x 17011 ; //, J, M y. 850 ; the others x 4'25 times : A-C, motor uniscles of the antcnnal scape. D-P, 

 motor muscles of the 3d coxa. A, B, the two ends, in very different states of contraction, of the 

 same fibre ; on one side the transverse strhe are near together, on the other very far apart. C, a 

 crushed and split fibre showing- a fibrous appearance, owing to the rupture of the radiated filaments, 

 and the separation of the longitudinal filaments. D, muscular disk seen in section, with two rows 

 of nuclei. E, a muscular fibre wit h three rows of nuclei. F, a nucleus, accompanied with coagulated 

 protoplasm, oozing from a previous break of the muscular fibre. G, nerve-terminations very near 

 each other on the same muscular fibre. If, longitudinal filaments, evenly covered with the coagulated 

 substance, and forming, throughout the mass of the fibre, continuous filaments. /, filaments widely 

 separated. J, longitudinal filaments showing the beginning of one of the transverse breaks which 

 isolate some of the disks. Ji, oblique view of a disk obtained by such a break, and of a fibre in 

 circular section, with an axial row of nuclei ; this piece comprises three stages of radiated filaments. 

 L, muscular fibre with a row of nuclei ; at the lower part, the nuclei have issued from a longitudinal 

 fissure in the fibre, and have remained attached in a chain. J)/", edge of fibre in which there is quite 

 a large, clear space between the sarciilemma and the rods. _A r , passage of the trachea, with the spiral 

 thread, into three capillaries with a smooth cuticula. O, elliptical disk from a fibre, with two rows 

 of nuclei, and showing a layer of radiated filaments. P, fragment (highly magnified) of the edge of 

 a disk seen in section. After Janet. 



A humble bee (Bombus terrestris) can carry while flying a load 

 0.63 of its own weight, and a honey bee 0.78 ; here, as usual, the 

 smaller insect is the stronger. 1 



1 It has been suggested to us by A. A. Packard that the power possessed by insects 

 of transporting loads much heavier than themselves is easily accounted for, when we 

 consider that the muscles of the legs of an insect the size of a house-fly (I inch long), 

 and supporting a load 399 times its own weight, would be subjected to the same stress 

 (per square inch of cross-section) as they would be in a fly 100 inches long of precisely 

 similar shape, that carried only its own weight; from the mechanical law that, 

 while the weight of similar bodies varies as the cube of the corresponding dimensions, 

 the area of cross-section of any part (such as a section of the muscles of the leg) 

 varies only as the square of the corresponding dimensions. In short, the muscles of 

 a fly carrying this great proportional weight undergo no greater tension than would 

 be exerted by a colossal insect in walking. 



