404 



AN ECONOMIC ENTOMOLOGY. 



are quite numerous, and the abdomen is conical in shape, con- 

 nected with the thorax by a very short and slender neck, or 

 pedicel, more resembling the true wasps than any other of the 

 species that we have been considering. 



There are several other families with similar habits, differing in 

 appearance to some extent, and varying in the character of the 

 insects used in storing their nests. Among the families contain- 

 ing the smaller species we find those types that burrow in pithy 

 plants and prefer small insects for provisioning their nests : — 

 flies, plant-lice, and small spiders being the most usual suppHes. 



Taken as a whole, all the digger-wasps are useful insects, and 

 they require for food, in the course of a season, a very large num- 

 ber of specimens injurious to plant-life. 



The "true wasps," or Vespidcs, are distinguished from the 

 ' ' diggers' ' by the fact that the fore-wings are folded longitudinally 

 when at rest, and this is a character easily seen and quite distinctive. 

 We have among them solitary and social forms, — the solitary 

 types so called because only the two normal sexes are present, and 

 because they do not live in colonies. There is a great variation 

 in habit, and we find species that bore in woody tissue, some 

 that inhabit pithy plants, some that burrow in the earth, and 



others that make mud 

 nests. The mud nests 

 vary in form and are 

 often quite pretty, those 

 of Eumenes resembling 

 a jug or vase attached to 

 the twigs and stems of 

 plants. It is not always 

 possible to distinguish be- 

 tween the cells and nests 

 of the diggers and those 



Fraternal potter-wasp, Eumenes fraterna.—a, of the trUC WaSpS, and 

 wasp ; b, its cell ; c, same broken open to show the nracticallv it is a matter 

 caterpillars stored in it. ^ . , 



oi no importance, because 

 the habits of the insects are similar, — that is, they store their 

 cells with insects upon which their larvae feed. All solitary 

 wasps are beneficial, therefore, and should be encouraged by the 

 farmer. 



