342 The University Science Bulletin. 



first stage in the history of this nest. No more cells were added un- 

 til near the time of maturity of the offspring. 



Hatching began May 30 with the three eggs which had been de- 

 posited on May 20. Two eggs deposited on May 21 hatched on May 

 31 and one on June 1. The incubation period of five eggs was ten 

 days and of one eleven days. Records of incubation were not com- 

 plete for the other eggs, but they required about the same time. 



The wasp larvae grew rapidly, but at an unequal rate. This was 

 apparently due to the fact that some were favored in feeding. The 

 first grub spun the cap, closing its cell for pupation June 9, and the 

 other cells of the first-hatched larvae were closed June 1, 13, 15, 17 

 and 21, and July 9, making the larval period vary from ten to 

 thirty-eight days. In contrast to this extreme variation, the period 

 required for pupation was exactly eighteen days in all instances, the 

 wasps maturing on June 27, July 1, 3, 5, 9 and 27. All were females. 



For two days after emergence from its cell the first wasp stayed 

 on the nest. After that it began going to the field, and soon was 

 doing most of the field work; that is, bringing in paper for nest 

 building and partially crushed insects for larval food. Caterpillars 

 were apparently the most frequent prey. The parent wasp stayed 

 at home, received supplies from the worker, and at first did most of 

 the feeding of the larvae and actual adding to the nest. As the num- 

 ber of offspring increased, there were always several on the nest 

 ready to meet a field worker and unburden it of its supplies. The 

 field workers also often engaged in feeding the grubs. 



Shortly before the emergence of her first offspring, on June 21, 

 the parent wasp began three new cells and deposited eggs in them. 

 Three more cells were started on June 27, and from then on building 

 progressed rapidly. By July 10 there was a total of thirty-one cells 

 in the nest, and all of the cells vacated by maturing wasps were 

 renovated and eggs were again placed in them. At the close of the 

 season a total of eighty-two cells had been built. 



This nest seemed to be fairly representative for rate of growth 

 and size. Two other nests which were started about the same time 

 were observed occasionally. On July 9 one had three wasps and 

 fourteen cells; the other had six wasps and twenty-four cells. At 

 the end of the season they had seventy-four and 102 cells, respec- 

 tively. The total number of wasps in any of the colonies was not 

 definitely known. 



The first male wasp appeared August 12, and after this for at 

 least three weeks there was a large emergence of drones. The time 



