LEPIDOPTERA. 161 
“Tt knew how to change its mancuvres. 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 
fother) sides 4.) =) 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. Réeaumur 
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 jaws 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. Réaumur saw this caterpillar work and raise in 
this way a large blade during one 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 
