312 INSECT ARCHITECTURE. 



with this glutinous matter, while they exclude every 

 fluid of a different quality."* When confined in an 

 open glass vessel, the goat-moth caterpillar will effect 

 its escape, by constructing a curious silken ladder, 

 as represented by Roesel. 



Caterpillars, as they increase in size, cast their skins 

 as lobsters do their shells, and emerge into renewed 

 activity under an enlarged covering. Previous to this 

 change, when the skin begins to gird and pinch them, 

 they may be observed to become languid, and indiffe- 

 rent to their food, and at length they cease to eat, and 

 await the sloughing of their skin.T It is now that 

 the faculty of spinning silk seems to be of great ad- 

 vantage to them; for being rendered inactive and 

 helpless by the tightening of the old skin around their 

 expanding body, they might be swept away by the 

 first puff of wind, and made prey of by ground-beetles 

 or other carnivorous prowlers. To guard against such 

 accidents, as soon as they feel that they can swallow 

 no more food from being half choked by the old skin, 

 they take care to secure themselves from danger by 

 moorings of silk spun upon the leaf or the branch 

 where they may be reposing. The caterpillar of the 

 white satin-moth (Leucoma salicis, Stephens) in this 

 way draws together with silk one or two leaves, similar 

 to the leaf-rollers (Tortricidce), though it always 

 feeds openly without any covering. The caterpillar 

 of the puss-moth again, which, in its third skin, 

 is large and heavy, spins a thick web on the upper 

 surface of a leaf, to which it adheres till the change 

 is effected. 



The most important operation, however, of silk- 

 spinning is performed before the caterpillar is trans- 

 formed into a chrysalis, and is most remarkable in 

 the caterpillars of moths and other four-winged flics, 

 * Spectacle de la Nature, vol. i. 

 t See Insect Transformations, chap, vii. 



