HYMENOPTERA 365 



one building its own series of cells in each of which is placed an egg 

 together with provision for the young. The cell is then closed and 

 probably forgotten by the mother wasp. An African eumenid wasp has 

 been observed, however, which does not gather provision in advance but 

 leaves the cell open and feeds the larva from day to day. 



The different species of eumenids differ greatly in methods of nest- 

 building; many are miners digging burrows in the earth leading to cells 

 in -which provisions are placed for their young; some make burrows in 

 wood, which they divide into cells by partitions of mud; some build their 

 nests in the stems of pithy plants or make use of any suitable cavity that 

 they find ; and others are mason or potter-wasps, making cells of earth, 

 which are built in holes, or on the surface of the ground, or attached to 

 twigs. 



Although the adult eumenids do not confine themselves to a carniv- 

 orous diet but often visit flowers to obtain nectar, they all provision 

 their nests with insects, which they have paralyzed with their sting; 

 usually only a single species of caterpillar is used for this purpose by each 

 wasp. 



Odynerus. — The greater number of our species of eumenids belong to 

 the genus Odynerus. In this genus the abdomen is sessile. The shape of 

 the body and frequently the coloration resemble those of the social wasps 

 known as yellow-jackets, although usually the body is more slender and 

 smaller. The common species are quite neighborly; and, owing to this 

 resemblance to the yellow- jackets they inspire us with a fear that is out of 

 all proportion to their will or ability to inflict pain. 



Many species of Odynerus are miners. Their burrows are to be found 

 both in level ground and in the sides of cliffs. Branching from these 

 burrows are short passages, each leading to a cell, from the ceiling of 

 which an egg is suspended by a slender thread; jM^fa 



and in which food is stored for the larva. In S^Wim 



the species that have been studied, this food JlPilk^ 



consists of small, paralyzed caterpillars. Some ""^^^^^^p^^^Zr^" 

 of the mining species while digging the burrow 

 build a turret over the entrance of it, made of :z - ~~ 



pellets of mud removed from the burrow (Fig. FlG 6o8 _ Tun . et over the 

 60S). The material of which the turret is com- ^[™ R ^ anTllT) S geminus ' 

 posed is used to fill up the burrow after the cells 



are finished. In digging the burrow and in tearing down the turret the 

 earth is softened with water, which the wasp brings in her mouth from 

 some pool or stream. 



Not all species of Odynerus mine in the ground; many burrowin the 

 stems of pithy plants, making a series of cells separated by partitions of 

 mud; other species will avail themselves of any convenient cavity in 

 which to make their nest, frequently utilizing the deserted nests of the 

 sphecoid-wasps known as mud-daubers. In this case a single cell of a 

 mud-dauber is divided by a transverse partition, making two cells for the 

 smaller Odynerus. One year these wasps plastered up many of the key- 

 holes in our house, including those in bureaus. 



The jug-builders, Eumenes. — The wasps of the typical genus_ of this 

 subfamily are potter- wasps which build nests that appear like miniature 

 water-jugs. The nests of our common species, Eumenes fraternus, are 

 often found attached to twigs (Fig. 609). In this genus the abdomen of 



