HYMENOPTERA. 645 



Asa rule, each species provisions its nest with a particular 

 «dnd of food. Some use only spiders for this purpose, some 

 plant-lice, some caterpillars ; and so on through the list. 



Very interesting and useful work can be done by the 

 student in the study of the habits of the digger-wasps and 

 of the solitary true wasps and solitary bees. Comparatively 

 few nests of either of these groups of insects have been 

 carefully described in this country ; and as each species 

 presents peculiarities of habits, the study is a very fascinat- 

 ing one. 



The nests are most abundant in sandy banks and in the 

 pith of sumach, elder, brambles, and other plants. Some 

 nests are dug in the earth in level places, and many are built 

 of mud and attached to the lower surface of stones or be- 

 neath the roofs of buildings. 



The nests made of mud should be carefully removed so 

 as not to break them, the nature of the provisions noted, 

 and the nest placed in a cage to breed the adult. When 

 the adult has been obtained, both nest and insect should be 

 mounted and placed in a collection. 



In many cases the cells of mining species can be re- 

 moved from the earth and the insects bred in a similar way. 

 But the easiest nests to study are those made in the pith of 

 plants. If dead branches of sumach or elder be split open 

 many of these insects can be found. If the branch be split 

 carefully the peculiarities of the nest can be observed with- 

 out injury to its occupants. Then if the pieces of the branch 

 be tied together the adult insects can be bred by placing the 

 nest in a glass jar or other cage, or in a bag of muslin, if the 

 branch is a long one. 



If a nest is provisioned with a paste made of pollen and 

 nectar, it is a nest of a bee ; but if it is provisioned with 

 spiders or insects, it belongs either to a digger-wasp or to a 

 solitary true wasp. We know of no way of distinguishing 

 between the nests of the last two except by breeding the 

 adults. 



