HABITS AND STRUCTUKE OF INSECTS. 87 



cell with looser mud. Thus she proceeds, constructing cell 

 after cell, going through the same mancBuvres with each one. 

 It has been observed that the wasp stings the spiders so 

 as to paralyze, but not to kill them. Hence they remain 

 alive but cannot struggle, and when the egg hatches the 

 little larva coming from it finds in these spiders a store 

 of food on which to feed. These are gradually eaten, and 

 thus room is made for the rapidly-growing larva which, hav- 

 ing eaten all the spiders, passes into its pupa state surrounded 

 by its brown chrysalis case, and finally emerges a perfect 

 wasp, when it softens the mud-walls of its nest, by a fluid 

 poured from its mouth, and gnaws its way out. 



Fig. 85. — Showing a Nest op Fotik Cells cut open : a, representing a Cell ■with the "Egf^ 

 at the Bottoin, and the remaininfr Space filled with Spiders ; &, the Larva full-grown, 

 after having consumed all the Spiders; c, the Pupa; and d, the Imago, or Perfect 

 Wasp, ready to come out. 



Fig. 51 shows one of these mud-wasps pinned. 



The pupils may collect these nests or cells in April or 

 May, and by June the wasps will be ready to come out. If 

 collected soon after they are made, the eggs may be found ; if 



