156 THE INSECT WORLD. 



left only its hinder part within. It moved its head forwards as far as 

 was necessary to enable it to seize a particle of earth. As soon as it 

 had got its load, it re-entered the interior of the cocoon. It deposited 

 the grain of earth, and came out again immediately, as it did at first, 

 to pick up another grain, which it carried likewise into the interior 

 of the cocoon. This operation it continued for more than an hour. 

 . The provision of materials being got together, the caterpillar 

 now devoted his whole attention to working them up. It began by 

 spinning over one part of the edges of the opening. After having 

 put over this a small band of very loose web, the caterpillar's head 

 left the opening, the insect went right back again into its cocoon, and 

 the head returned to the opening loaded with a little grain of earth, 

 which it entangled in the silky threads. It then entangled in them 

 two or three, or a greater number of grains, according to the quantity 

 of threads it had spun. It bound them into these with other threads, 

 after which it drew threads over the edges of another part. By thus 

 going round the whole rim of the opening, and by carrying and 

 fixing the grains of earth in the threads which were the last stretched 

 over the opening, it rendered its diameter smaller and smaller." 



It was by working with its head that our mason gave to the new 

 wall of its cocoon the necessary curvature. It was interesting to 

 know how, as it could no longer put out its head, it could stop up 

 the orifice. 



"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 succes- 

 sion the whole of the web was covered with grains of earth 



It was not satisfied 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, shows to what a 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 triangular appendages (Figs. 122, 123). 



