THE PUPA OR CIIETSALIS. 99 



of the down that covers the seed-vessels of this 

 tribe of trees. The little Caterpillars know how 

 to render their so-formed structure completely water- 

 proof, by " felting" it with a fluid with which 

 Nature has furnished them for that purpose. The 

 house therefore serves them, in time of need, as a 

 boat also, if unluckily blown by the March or 

 April winds from the branches where they feed 

 into the water below ; in which case they float se- 

 curely to shore in their little life-boat. Branches 

 of willow might be sought when in blossom in the 

 early spring, on which some of these interesting 

 little architects and ship-builders would be pretty 

 sure to be found ; and by placing the said branches, 

 with the stalks in water, in the Vivarium, their 

 transformations might be watched. The branches 

 might also be made to lean over the tank, and some 

 of the larvae shaken into it for the purpose of ob- 

 serving their escape in the little floating houses. 



Among the better known cocoons or chrysalis- 

 houses of the larger Moths, the first place must 

 always be given to that of the Silk -worm, the finely 

 spun web of which has for several thousands of years 

 furnished the silk of commerce to Oriental nations, 

 though the knowledge of the Worm and the me- 

 thod of procuring its silk has only been generally 



