THE WHITE-FOOTED WASP 43 



The egg hatches in forty-eight hours, resulting in the character- 

 istic wasp grub of thirteen segments. It commences feeding at once 

 upon the stored spiders, first drawing off the soft parts, and later 

 returning to less delicate food. During the first day of its life the 

 larva grows only two millimeters. On the second and third days it 

 averages five millimeters each. On the fourth day it goes back to 

 two, grows eight on the fifth and finishes with a growth of one milli- 

 meter on the sixth and last day of its meal. The spiders are now 

 entirely consumed and the grub measures twenty-six millimeters in 

 length. 



Without pausing for a moment to rest, the full-grown larva now 

 sets about to lay the foundations of its elaborate cocoon. The insect 

 is awkwardly placed at the outset, living as it does in a cell whose 

 perpendicular walls are several times its own length, but fortunately 

 at this period of its life it is endowed with an unusually tacky skin. 

 This stickiness serves a special purpose, enabling the grub to remain 

 safely in the top or center of its cell without the slightest danger of 

 tumbling down to the mortar plug separating it from the cell below. 



From its lofty position and in total darkness, the grub first throws 

 out several bands of silk, fastening them in various places about the 

 reed \valls. It makes no choice of its own, but simply fastens each 

 successive thread to the first point of contact. Some of the strands 

 pass to points above the spinner, some below, and still others across 

 the middle of its body to the wall beyond. At length the grub finds 

 itself more or less enclosed in a delicate silken net through the strands 

 of which it may still poke its head. 



Thirty or forty new threads are now extended from the top of the 

 growing cocoon. They emerge from various points in a circle, and 

 are fastened to the cell wall above. The larva now returns to its 

 original network, within which it spins a firm torpedo-shaped cover- 

 ing, slightly wider than its own body, nineteen millimeters in length 



