THE BIOLOGY OF THE MUD-DAUBING WASPS 57 



The number of cells varied from 1 to 17 to the nest. The 



adults emerged the following June. The contents of these 171 



cells were as follows: 



No. Per cent 



Cells producing good adults 47 27 



Cells filled and sealed without egg 18 10 



Cells sealed empty 16 10 



Cells unsealed, containing few spiders 



Cells unsealed and empty 8 5 



Cells containing dead larvae and insufficient food 3 2 



Cells containing dead larvae and sufficient food 1 



Cells containing dead prepupae 29 17 



Cells containing dead pupae 3 2 



Cells containing dead adults 4 2 



Cells parasitized by Melittobia 37 22 



Cells parasitized by Anthrenus 1 



Cells parasitized by Diptera 4 2 



» 



171 99 + 



We shall here compare this lot only briefly with the preceding 

 winter brood from a different locality, and go into fuller com- 

 parison with the summer brood to follow. 



There is a conspicuous difference in the proportion of adults 

 emerging. Here 27 per cent, of the cells built produced adults, 

 yet even this is not enough to maintain the population. In 

 this lot the nests contained ,pn an average only 5.5 cells; if they 

 had averaged 9 cells to each mother, as the Kansas material 

 did, then the population would just maintain itself under the 

 rate of elimination shown here. The principal differences in 

 the mortality in the groups is found in the larval and prepupal 

 .stages and the parasitized cells. The lower percentage of loss 

 here just balances the gain in the increase in the productiveness 

 of the population. 



THE ST. LOUIS SUMMER BROOD 



The second brood, or first summer brood, emerged from nests 

 built in June and July of the same summer. The 110 nests 

 which furnish the data of this group were gathered during July 

 at Meramec Highlands, St. Louis, Mo. Owing to the earliness 

 of the season, the greatest number of cells in a nest was 8, and 

 the total number of cells examined in this lot was 438. Their 

 contents were as follows: 



