58 PHIL RAU AND NELLIE RAU 



No. Per cent 



Cells producing good adults 225 51 



Cells sealed with spiders but no egg 27 6 



Cells sealed empty 28 6 



Cells unsealed, with few spiders 1 



Cells unsealed and empty 16 4 



Cells containing dead larvae and insufficient food 3 1 



Cells containing dead larvae and sufficient food 9 2 



Cells containing dead prepupae 42 10 



Cells containing dead pupae 13 3 



Cells containing dead adults 8 2 



Cells parasitized by Melittobia 32 7 



Cells parasitized by Anthrenus 32 7 



Cells containing Diptera or Trypoxylon clavatiim 2 



438 99 + 



It is at once apparent that this summer brood was far more 

 prosperous than the winter broods just considered. We are 

 not at all surprised at this when we consider that their whole 

 development was accomplished during a brief period of favorable 

 conditions. They did not have to endure the rigors of winter 

 and the increased chances of casualty incident to the prolonged 

 period of dormancy. 



Let us take up briefly a comparison of the causes of failure 

 in the two broods. In the first entry in the tables, viz., the 

 per cent, of the cells which brought forth good living adults 

 we are startled by 51 per cent, of the summer cells being fruitful 

 against only 4 per cent, and 27 per cent, of the winter crops 

 of cells. In an attempt to account for this we shall compare the 

 other classes, to locate the discrepancy. The per cent, of cells 

 properly made and provisioned, but sealed without an egg, 

 is noticeably larger in the winter broods. Since we found in 

 a previous chapter (see p. 47) that the large nests were no 

 more likely than the small ones to be affected thus, we cannot 

 attribute this difference to the smaller summer nests. It might 

 be, however — this is mere conjecture — that a part at least of 

 the winter nests are constructed by the wasps late in the fall, 

 in their feeble old age, and hence a larger proportion of these 

 eggless cells might occur than in the nests built by the vigorous 

 young mothers early in the season. In other words, this kind 

 of failure might be attributed to some real physical inability 

 of the parent, and not to mere carelessness or faulty instinct. 



The next five groups are surprisingly similar, down to the 

 number of larvae which died of starvation, which is 1 or 2 per 

 cent, in all broods. Hence we have every reason to believe 



