DEFENSES OF THE LESSER ANIMALS. 487 



but which widen as the hirvsB grow, feeding themselves from the 

 parenchyma in which they work, and at the same time obtaining a 

 defense against external injurious influences and disturbances. They 

 usually leave their burrow, when about to assume the chrysalis state, 

 by a little hole that may be found at the extreme end of the excava- 

 tion, and either fall to the ground or make a cocoon, attached to 

 some plant, in the air. Other burrowing larvae bury themselves in 

 the ground. 



For the preservation of the chrysalis, Nature has provided many 

 insect-larvoe with the faculty of spinning, and organs for the purpose. 

 This function is so extraordinarily developed in the larvae of the but- 

 terflies that a whole group of that order have been called *' the spin- 

 ners " ; while many of these spinners — the silk-worms — have been 

 made serviceable to human civilization. Before the spinning larva 

 advances to its last change of skin, it selects a sheltered, dry spot — 

 between leaves, on bark, in a hedge, in turf, or on a post — and then, 

 drawing from the spinning-glands situated under its neck and between 

 its head and fore-feet fine silken threads, it prepares an ample, firm, 

 and intricate web of flock-silk for its envelope. Having completed 

 its cocoon, it shakes off its old skin, and lays itself to sleep in this 

 soft but solidly-made bed, while its pupa-skin hardens and it awaits 

 the time for its next transformation ; and only when disturbed from 

 without does it show by some spasmodic motion of the posterior seg- 

 ment that it can still feel, and that its pupa-rest is not a death-sleep, 

 but only a temporary repose. If the larva is provided with a hairy 

 skin or bristles, they become interwoven with the cocoon, and a com- 

 posite texture is formed, which man must be careful how he touches, 

 or the bristles will sting his fingers and make them smart. Naked 

 caterpillars, or larvae, weave, like the real silk-worm, cocoons of pure 

 silk, or, like the false-caterpillars, and the larvic of wasps, ants, and 

 bees, transparent, cylindric-oval envelopes of a consistency like that 

 of parchment or waxed paper. The naked caterpillars of the Iler- 

 mione moth make a kind of roof of pieces of bark over a hollow which 

 they have excavated in the ground for their bed ; and a hairy larva 

 provides for itself in a similar manner. Many other larvae go for the 

 security of their pupae into or upon the ground, where they prepare, 

 from leaf-dust, moss, and grains of sand, a ball rough on the outside 

 but smoothly finished within, or simply a hole in the ground, as an 

 envelope. 



Arrived at last at its perfect and free state, the insect is efficiently 

 protected by that " mimicry " which has been much discussed by Wal- 

 lace and other writers, or the likeness in color, and sometimes in other 

 qualities, which it presents to objects that are associated with its 

 most accustomed haunts. Some instances of this mimicry may be 

 observed among higher animals, but it is most conspicuous and sig- 

 nificant with insects. We need only refer to the appearance of dif- 



