256 INSECT LIFE 



XVIIl 



fresh materials from outside, tearing away a corner 

 of the protecting curtain, and through this window 

 grasping the materials needed. The cocoon is still 

 incomplete — wide open at the upper end and without 

 the spherical cap needed to close it. For this final 

 bit of work the grub provides itself abundantly with 

 sand, and then pushes away the heap before the 

 entrance. A silken cap is now woven and fitted 

 close to the mouth of this primitive basket. On this 

 silken foundation are deposited, one by one, the sand 

 grains kept in the interior and cemented with silk- 

 spittle. This lid completed, the larva has only to 

 give the last finish to the interior of the dwelling 

 and glaze the walls with varnish, to protect its tender 

 skin from the roughness of the sand. 



The hammock of pure silk and the cap which 

 later closes it are evidently only scaffolding intended 

 to support the masonry of sand and to give it a 

 regular curve. One might compare them to the 

 constructions used by builders when making an arch 

 or vault. The work being completed, the silken 

 support disappears, partly lost in the masonry, and 

 partly destroyed by contact with rough earth, and 

 no trace remains of the ingenious method employed 

 to put together a construction perfectly regular, yet 

 made of a material so little coherent as is sand. 

 The spherical cap which closes the original basket is 

 a separate work, adjusted to the main body of the 

 cocoon. However well the two pieces are fitted and 

 soldered, the solidity is not such as the larva would 

 obtain had it built the whole dwelling continuously. 

 Thus, on the circumference of the cover there is a 

 circular line less capable of resistance, but this is not 



