HABITS AND BIOLOGY OF THE COMMON WASP 327 



character of the particular season, appears in this case to 

 have been very high. The number of living workers in the 

 nest at the end of July was 417. But the number of 

 individuals which had hatched up to that time is represented 

 by the numbers of empty cells reoccupied by the members 

 of the second and third broods. The stages of the second 

 brood were distributed in 680 cells, those of the third brood 

 in S6 cells. From the former one set of pupae had hatched, 

 from the latter two sets, so that the total of workers hatched 

 was approximately 680 plus 172, or 852 individuals. The 

 deaths, therefore, during the 3 months' existence of the nest 

 reached 435. But during the first month no pupae had 

 hatched, so that this mortality is limited to the two months, 

 June and July. 



It is impossible to state with any accuracy the rate of 

 mortality per day, but from a somewhat complicated 

 calculation,^ with the details of which I need not wear)' my 

 readers, I estim.ate that the death-rate at the end of 

 July must have been not less than 85 a day, and that the 

 life of a worker is limited to between 3 and 4 weeks. The 

 above may be considered a normal death-rate due to 

 physiological exhaustion at an active period of the nest's 

 existence, in contrast with the much heavier but abnormal 

 death-rate due to external causes, which occurs in late 

 autumn when the colony is hurrying to extermination. 



Amount of Earth Removed. — Taking the diameter of the 

 underground cavity in which the nest hung at the minimum 

 measurement of 9 ins., the total amount of earth removed 

 by the wasps was 382 cub. ins. Since 852 workers spent 

 part of their time in this labour, for which they seem ill- 

 fitted, each must have removed grain by grain almost \ a 

 cubic inch during its working life. 



The Later Growth of the Common Wasp's Nest. 



The nest which has furnished the above deductions was 

 examined in the end of July, some time before the wasp 



' Based upon the probable numljcr of workers which built the cells 

 in which larvae of the first brood were found. 



