330 Insect Architecture. 



CHAPTER XVII. 



STRUCTURES OP SILK SPUN BY CATERPILLARS, INCLUDING THE 

 SILK-WORM. 



" Millions of spinning- worms, 

 That in their greeu shops weave the ?rnooth-hair'd silk." 



MILTON'S Comus. 



A LL the caterpillars of butterflies, moths, and, in general, 

 ^*- of insects with four wings, are capable of spinning silk ; 

 of various degrees of fineness and strength, and differing in 

 colour, but usually white, yellow, brown, black, or grey. 

 This is not only of advantage in constructing nests for them- 

 selves, and particularly for their pupae, as we have so 

 frequently exemplified in the preceding pages, but it enables 

 them, the instant they are excluded from the egg, to protect 

 themselves from innumerable accidents, as well as from 

 enemies. If a caterpillar, for instance, be exposed to a gust 

 of wind, and blown off from its native tree, it lets itself 

 gently down, and breaks its fall, by immediately spinning a 

 cable of silk, along which, also, it can reascend to its former 

 station when the danger is over. In the same way it fre- 

 quently disappoints a bird that has marked it out for prey, 

 by dropping hurriedly down from a branch, suspended to its 

 never-failing delicate cord. The leaf-rollers, formerly de- 

 scribed, have the advantage of other caterpillars in such cases, 

 by being able to move as quickly backwards as forwards ; so 

 that when a bird puts in its bill at one end of the roll, the 

 insect makes a ready exit at the other, and drops along its 

 thread as low as it judges convenient. We have seen cater- 

 pillars drop in this way from one to six feet or more ; and 

 by means of their cable, which they are careful not to break, 



