OBSERVATIONS ON ANTS. I/ 1 



left-hand end the bare copper was surrounded by ice. When all 

 was established, the interior surface of the nest, tested by remov- 

 ing a slide and covering the aperture with a wad of cotton 

 through which passed a centigrade thermometer, showed a range 

 of temperature from 10 C. or 14 F. at the left-hand end to 

 60 C. or 140 F. at the right-hand end. The air was usually 

 a degree or two lower than the enclosing surface that warmed it. 



I then separately introduced into this nest different groups of 

 the above-named genera, workers, larvae and pupae, in each case 

 leaving the group to collect its scattered young at whatever por- 

 tion of the nest the workers should themselves select. With 

 great unanimity the different groups chose a place in the nest 

 where the temperature was from 24 to 27 C. or 76 to 82 F., 

 the temperature being taken from the surface against which the 

 ants and young rested. 



This is the temperature at which I have observed greatest 

 activity and reproductivity in my artificial nests. I have also, 

 when the temperature of the air was somewhat below 22 C. or 

 70 F. repeatedly observed wild colonies of Stcnauuna fnlvuui. 

 where the larvae and pupae had been carried outside the nest 

 and laid among the grass stems for greater warmth, despite the 

 daylight from which the ant-nurses commonly withdraw the 

 young. 



In 1901 I froze 1 Stcnaimna fuhmm, queens, workers and 

 young, for twenty-four hours, the thermometer going down to 

 5 C. or 23 F. The ants were gradually thawed and all sur- 

 vived. The frozen eggs, larvae and pupae developed perfectly 

 later on. 



Below 15 C. or 60 F. the ants are noticeably sluggish. In- 

 crease of activity accompanies increase of temperature from freez- 

 ing point, where they are wholly inert and apparently lifeless, up 

 to a degree where they swoon from the intensity of the heat. In 

 the copper nest the ants manifested discomfort or distress at any 

 temperature above 30 C. or 86 F. At 35 C. or 96 F. the 

 smallest ants swooned, and I could induce no ant to voluntarily 

 move to a hotter portion of the nest, even when driven by sun- 



! "A Study of an Ant," Proceedings of the Aiodemy of A'atural Sciences of 

 'l.hia, July, 1901, p. 441. 



