88 ENTOMOLOGY 
hyaloplasm (isotropic). The spongioplasmic threads of the 
long bands extend longitudinally and those of the short bands 
(“ Krause’s membrane ’’) radially, in respect to the form of 
the fiber. Moreover, the attenuated extremities of the longi- 
tudinal fibrillee connect with the radial fibrillz, the points of 
connection being marked by slight thickenings, or nodes, 
which go to make up Krause’s membrane. 
Under nervous stimulus a muscle shortens and thickens 
because its component fibers do, and this in turn is attributed 
to the shortening and thickening of the longitudinal fibrille. 
When the stimulus ceases, the radial fibrille, by their elas- 
ticity, possibly pull the longitudinal ones back into place. ‘The 
last word has not been said, however, upon this perplexing 
subject. 
Muscular Power.—The muscular exploits of insects appear 
to be marvellous beside those of larger animals, though they 
are often exaggerated in popular writings. The weakest in- 
sects, according to Plateau, can pull five times their own 
weight and the average insect, over twenty times its weight, 
while Donacia (Chrysomelide) can pull 42.7 times its weight. 
As contrasted with these feats, a man can pull in the same 
fashion but .86 of his weight and a horse from .5 to .83. How 
are these differences explained ? 
It is incorrect to say that the muscles of insects are stronger 
than those of vertebrates, for, as a matter of fact, the contrac- 
tile force of a vertebrate muscle is greater than that of an 
insect muscle, other things being equal. The apparently 
greater strength of an insect in proportion to its weight is 
accounted for in several ways. The specific gravity of chitin 
is less than that of bone, though it varies greatly in both sub- 
stances. Furthermore, the external skeleton permits muscu- 
lar attachments of the most advantageous kind as compared 
with the internal skeleton, so that the muscles of insects sur- 
pass those of vertebrates as regards leverage. ‘These reasons 
are only of minor importance, however. Small animals in 
general appear to be stronger than larger animals (allowing 
