TEMPERATURE IN THE DEVELOPMENT OF ANTS. 365 



periods of low or of high temperature, but deposited eggs after 

 the middle of June, 1905, when the summer heat rose to 78 F. 



OTHER EXPERIMENTS. 



Dr. Field had a nest of workers of Formica pallidc-fnlva fuscata 

 in which many eggs were deposited in March, 1905, when kept 

 at a'temperature of from 75 to 85 F. and the issue of these 

 eggs passed safely through the larval and pupal stages at the 

 same temperature. Dr. Field had also a nest of Camponotus 

 pc nnsylv anicit s workers who failed to rear their larvae to pupation 

 in the summer of 1904, but who, under the influence of the above 

 named high temperature brought three to pupation in January, 

 1905. 



Dr. W. M. Wheeler writes to me that Formica consodans 

 workers in his artifical nests deposited many hundreds of eggs, in 

 March, 1905, in a room whose temperature never rose above 60 

 F. or 15 C. 



It appears that the time of development may be altered by 

 change of the prevailing temperature and that an intervening 

 period of recuperation will be maintained in spite of a continued 

 temperature-stimulus. Other factors being equal, the develop- 

 ment of the eggs within the ovaries, the deposit of the eggs, the 

 feeding and growth of the larvae, the pupation and the hatching, 

 all appear to be determined by temperature. The degree of heat 

 suiting the species probably varies for the different stages of 

 development. 



All the ants involved in my experiments had the same food- 

 supply, the same daily temperature, and similar housing. They 

 were abundantly provided with insect-food and with a variety of 

 sweets. They always appeared to be in excellent health, and 

 hardly any deaths occurred in any of the nests mentioned. It is 

 therefore difficult to refer behavior so varied to other cause than 

 the varying effects of the same temperature on unlike species of 

 ants, or to avoid the inference that in different species the young 

 develop best at different degrees of heat. 



Among the ant-young observed by me, none has developed at 

 a temperature below 70 F. ; while long exposure to a degree of 

 heat above 90 F. manifestly causes injury. Two minutes ex- 



