52 THE SOLITARY WASPS. 



until the seventh and then spun its cocoon. (PL XL, fig. 6.) 

 If we suppose that two days passed before the hatching of the 

 egg the larval life lasted for six or seven days. 



As the flies in the nest were all partially destroyed we know 

 nothing of their condition when they were brought in, but dur- 

 ing the summer we took many stalks which had been filled by 

 stirpicola and made notes on the state of the contents. A de- 

 scription of one of these will serve as an example of all the rest. 



On August ninth we opened a stalk which had been partly 

 filled. The upper cell had just been stored, no pith partition 

 having been made above it, and no egg yet laid. It contained 

 twenty-three flies of the species Opthirsia punctipennis, all of 

 them dead, though plump and fresh. We examined them care- 

 fully but they had been killed, not paralyzed. They had been 

 packed in very closely. The cell just below contained twenty- 

 two flies of the same species, the larva having just begun to eat. 

 All of the flies were dead. We took them as well as those of the 

 first lot and examined them, one by one under a two-thirds ob- 

 jective, lest there should be some mistake as to their condition. 

 The third cell contained twenty-two flies which were dead, as 

 was also the larva, which had eaten only five abdomens. In 

 the fourth and last cell were twenty flies, all dead. The larva 

 had eaten parts of ten of them and was still at work. 



In almost every instance the flies were all dead although once 

 in a long time we found one which gave a slight response to 

 stimulation. In many cases we found the larva eating them 

 after they were dry: thus the evidence of stirpicola still further 

 confirms us in our belief that the health of the growing larva does 

 rot at all depend upon its being furnished with fresh food. 



All the pupae that we have kept have wintered in the cocoon 

 and have come out in the spring. 



