ROADSIDE LIFE. 263 



change to pupae without making cocoons. After a 

 time the pupas change to adult insects, which dig their 

 way out from the nest, and in turn build similar nests 

 for their young. In leaving the nest the newly devel- 

 oped adults pass out through the opening at the up- 

 per end. It follows from this that the youngest of 

 the brood — the one in the cell last made-r-is able to 

 emerge first, each adult being obliged to wait till 

 those above it are out of the way before it can escape. 



The nests of solitary bees can be recognized by 

 the fact that they are provisioned with a paste made 

 of pollen and nectar ; and, so far as I have observed, 

 the partitions in the nests of solitary bees are always 

 made of vegetable matter. Sometimes the partitions 

 are made of pith, sometimes of chewed-up leaves, 

 and in the case of certain large carpenter-bees the 

 partitions are built of small chips fastened together 

 in a spiral. 



The nests of the solitary true wasps and those of 

 the digger-wasps are provisioned with animal matter, 

 each species using a particular kind of food. Some 

 use only spiders for this purpose, some plant-lice, 

 some caterpillars, and so on through the list. In 

 each case the creatures stored in the nest are not 

 killed, but are stung in such a way as to be paralyzed. 

 Here they lie helpless till needed as food by the 

 larva that hatches from the egg laid with them. 



The solitary wasps and the digger-wasps that 

 build their nests in pithy plants also agree in usually 

 making the partitions in their nests of mud. In fact, 

 I know of no way of distinguishing between the nests 

 of these two groups of insects except by breeding the 

 adults. This, however, can be done easily. 



