AN ECONOMIC ENTOMOLOGY. 



connected with the thorax by means of a long stalk or pedicel. 

 These belong to the family Sphecidcs, of which the majority 

 build their nests underground and provision them with spiders, 

 caterpillars, or other larvae. Others, known as " mud-daubers," 

 species of Pelopoeus, plaster their nests against out-houses, in all 



sorts of corners and under all sorts of 

 Fig. 456. shelters. They are sometimes built 



singly, but usually in groups, and may 

 consist of either a shapeless mass of 

 mud, or may be regularly arranged, 

 often with ribbed sides. The insects 

 that build these nests are either metal- 

 lic blue, or black marked with yellow, 

 and here the pedicel connecting the 

 abdomen with the thorax is unusually 

 A mud-dauber, Peiopcus ^ A^rv^^x, The mud is Carried 



species. 



by the insect with its forelegs and jaws, 

 and is appHed carefully, pellet by pellet, to the nest, until the 

 cells are completed. Then they are stored with some one kind 

 of insect as food for the larva. If the insect begins on caterpillars, 

 it continues to collect caterpillars, all of the same species, stinging, 

 as already described, so as to paralyze them, and then packs 

 them away in the cavity as closely as possible. Finally, when a 

 cell is full, an egg is introduced ; and now, when the young wasp 

 hatches, it finds food in abundance at hand, and simply lives upon 

 this supply, taking one caterpillar after another, or one spider 

 after another, as the case may be. Some small species store their 

 nests with plant-lice. These insects are to be considered as de- 

 cidedly beneficial, and if the nests are sometimes unsightly and 

 the wasps themselves a nuisance, yet, taken all in all, they deserve 

 encouragement. The number of caterpillars destroyed by them 

 in the course of a season is enormous. I have counted thirty 

 canker-worms in a single cell, and have sometimes opened nests 

 in which there were an even greater number of small Tortricid 

 caterpillars. Any insects which destroy as many caterpillars as 

 do these wasps deserve our best consideration and should not 

 be wantonly destroyed. Another peculiarity to be noticed in 

 opening the nests is, that the insects, whether caterpillars or 

 spiders, are all of just about the same size, as if the mother had 



