364 ADELE M. F1ELDE. 



pupa-stage, and all these eggs and their issue had disappeared 

 before March 19. On March 26 this nest was removed to a 

 room having a temperature of 70 F., and these ants ceased from 

 egg-laying until the temperature again rose to more than 80 F. 

 in the following July. The young larvae from the July eggs 

 rapidly disappeared in the intense heat of July, 1905, and only 

 five of them spun cocoons. It seems that the development of 

 the eggs of this species demands a high temperature, while the 

 development of the larvae requires a lower degree of heat. 



Dr. Irving A. Field, keeping a nest of one hundred and fifty 

 worker-ants of this species, at Harvard University, gives me the 

 following account of said nest : " The ants all hatched between 

 August 20 and September 23, 1904. They laid no eggs until 

 after November 30, when the nest was placed in a chamber 

 having a temperature of from 75 to 85 F. Between Decem- 

 ber 30, 1904, and January 9, 1905, about a hundred and fifty 

 eggs were laid, all of which were subsequently addled or else 

 were eaten by the ants. But between June 6 and 13, 1905, 

 about sixty eggs were laid, and from these, in natural summer 

 temperature, many larvae safely passed to the pupa-stage." 



EXPERIMENT E. 



I had one group of virgin workers of Stcuannna fnhnun two 

 years old ; one group of virgin workers of Stenamma fulvum one 

 year old ; and one group of virgin workers of Camponotus amcri- 

 canns newly hatched, that deposited no eggs during Septem- 

 ber, October and November, 1904, when they were kept at a 

 temperature of about 70 F. But in all three of these groups, 

 eggs that produced larvae were deposited between November 20, 

 1904, and March 26, 1905, when they were kept at a tempera- 

 ture of from 82 to 85 F. ; and all were again subjected to a 

 completely arrested development of the young when the tempe- 

 rature fell to 70 F. between the end of March and the middle 

 of June, 1905. 



Groups of virgin workers of Formica Schaufussi and of Formica 

 neogagates, housed, fed, and kept at the same daily temperature 

 as were the above named ants, laid no eggs during either the 



