THE EUMENIDAE 329 



tained any causes, climatic, environmental or hereditary, to 

 account for such variations. This variability will be easily 

 noted from the tabulaton of a few typical cases, as follows : 



Spun 

 i 4th day 

 i 5th day 



i 4th day 

 i 5th day 

 i 8th day 

 i 5th day 

 i 5th day 



On August 2 we exhumed a three-fourths grown larva, 

 with its last caterpillar. We gave it three more, which it 

 eagerly devoured. After five days more it began to spin. 

 It was unable to construct its cocoon normally in the tin 

 box; so we made in the box a nest of tiny bits of soft paper. 

 After that it succeeded better in covering itself, but we 

 could still see the insect within. Not until August 19, or 

 twelve days after first spinning, did it transform into a 

 mummy-like pupa within the web. On September 12, after 

 a pupal period of thirty-six days, an adult female emerged. 

 There is a possibility that the transformation of this indi- 

 vidual may have been delayed by the impeded construction 

 of the cocoon. This adult was kept in a cage and lived on 

 sugar-water for eight days. This, too, would indicate that 

 at least two generations emerge each year. 



One of the perplexing problems is the question of how 

 the wasp in the lower cell, when adult, can emerge without 

 injuring its younger brother in the cell above. To be sure, 

 they probably lie dormant all winter and are ready for 



