HYMENOPTERA. 



6 5 I 



thorax is not prolonged backward on each side to the base 

 of the fore wing. But the most striking characteristic is 

 that the first segment of the abdomen is 

 generally narrowed into a long, smooth, 

 round petiole (Fig. 772), which suggests 

 the popular name given above. The ve- 

 nation of the wings of one of our more 

 common species is represented by Fig. 773. The fore wing 



FIG. 772. Pelopceus 

 cementarius. 



FIG. 773. Wings of Pelopceus cetnentarius. 



in this family has three closed submarginal cells (2d III, III B , 

 and III 4 ), and the last branch of vein V (vein V 3 ) arises be- 

 yond the end of the 2d cell III. Most of the species burrow 

 into sand-banks, and provision their cells with caterpillars 

 and spiders. But those best known to us are the mud- 

 daubers. These belong to the genus Pelop&ns (Pel-o-pce'us). 

 They make nests of mud attached to the lower surface of 

 flat stones or to the ceilings of buildings. These nests usu- 

 ally have the form of several tubes an inch or so long placed 

 side by side, and are provisioned with spiders. 



The mud-daubers may be seen in damp places collecting 

 mud for their nests, or exploring buildings in search of a 

 place to build. They have a curious habit of jerking their 

 wings frequently in a nervous manner. 



About seventy species of this family occur in this country. 



