LEPIDOPTEEAs 161 



" It knew how to change its manoeuvres. When the opening 

 was reduced to a circle of only a few lines in diameter, it drew 

 threads from a point on the circumference to another on the 



other side Thus the opening was covered in with a rather 



open net- work As soon as this web was finished, it got a 



grain of earth (which it had laid by until it was wanted), brought 

 it up, placed it against the web, and by pushing and pressing it, 

 made it pass through the web until it reached the exterior. 

 And so in succession the whole of the web was covered with 



grains of earth It was not contented with rendering the 



exterior of this place exactly like the rest of the shell ; it fortified 

 it thoroughly ; it added to it, one after another, layers of grains 

 of earth till it was as solid and as thick as the rest." 



The larva of Pyralis corticalis, which is found on oak trees, 

 in the month of May, exhibits to what point these little insects 

 carry their industry in the construction of their cocoons, in 

 the choice of their materials, in their manner of working them 

 up, and in the forms they cause them to assume. Reaumur 

 one day saw this caterpillar on a small branch, between two tri- 

 angular appendages (Figs. 122, 123). This was the beginning of a 

 cocoon. Each triangular blade was composed of a great number 

 of small, thin, rectangular plates, taken from the bark of the 

 twig. The caterpillar detached with its teeth a small band of 

 bark, and fitted it on, and adjusted it with admirable precision 

 against the edge already formed. It then fixed it securely with 

 silk threads. Reaumur saw this caterpillar work and raise in 

 this way a large blade during an hour and a half. 



"When one sees/' he says,* "an insect which, to con- 

 struct a cocoon, begins by collecting together an infinite number 

 of small plates of bark in order to compose of them two flat 

 triangular blades; which, to gain its end, takes means that 

 seem so roundabout, although they are the most ' suitable and 

 the quickest it could adopt, one is very much tempted to con- 

 sider such an insect, when one sees, it thus acting, possessed of 

 reason." 



These two blades are at last transformed into a regular cocoon. 

 The little animal, which is at the same time architect, cabinet- 



* Mem. 12, vol. i., p. 487. 

 M 



