HYMENOPTERA 953 



The different species of eumenids differ greatly in habits; many 

 are miners digging burrows in the earth leading to cells in which pro- 

 visions 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 

 carnivorous 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. 



A remarkable feature that has been observed in the nesting habit 

 of many eumenids and perhaps is true of all, is that after the cell is 

 prepared the egg is suspended by a slender thread from the ceiling 

 or side of the cell. In some cases, at least, this is done before the pro- 

 visioning of the nest is begun. An African species, Odynerus tropicdlis, 

 the habits of which are described by Roubaud ('i6) does not provision 

 its cell with prey amassed in advance, but feeds its larva from day to 

 day with small, entire, paralyzed caterpillars, and does not close the 

 ceil until the larva has completed its growth. 



The following examples will serve as illustrations of the habits of 

 members of the subfamily. Among the more detailed accounts of the 

 activities of some of our species are those of Peckham and Peckham 

 ('05), Hartman ('05), Isley ('13) and Rau and Rau ('18). For a 

 general account of the habits of these insects see Roubaud ('16). 



Odynerus. — The greater number of our species of eimienids 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 neighbor- 

 ly; 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. ,j«^5ffl©8^ 



Many species of Odynerus are miners. .^^^^^ 



Their burrows are to be found both in level ^^^^^ 



ground and in the sides of cliffs. Branch- ______^^ ^^_^-::^g-_ __^ 



ing from these burrows are short passages, "^^ri'l^^^ ffis^^ ^^izr'^ 



each leading to a cell, from the ceiling of rrzzEEir-^ — 



which an egg is suspended by a slender " 



thread; and in which food is stored for the Fig. 1185. — Turret over the 

 larva. In the species that have been stud- burrow of Odynerus gem- 

 ied, this food consists of small, paralyzed ^■"«^- ^^^^^^ ^^^ ^^^ Rau.) 

 caterpillars. Some of the mining species 



while digging the burrow build a turret over the entrance of it, made of 

 pellets of mud removed from the burrow; one of these turrets is 

 figured by the Raus (Fig. 1 185). The material of which the turret is 

 composed is used to fill up the burrow after the cells are finished. 



