THE DEl'ELOPMENT OF AXTS. 83 



as lung or even longer in many species of Cainponotiis and Prcuolcpis, 

 whose sexual forms do not mate till the following spring. The lon- 

 gevity of the workers is certainly much greater than that of the males. 

 Lubbock (1894, p. 12) had workers of Formica cincrca that lived 

 nearly five years, workers of F. sangniiiea that had lived at least five 

 years, and some individuals of F. fusca and Lasius nigcr that attained 

 an age of more than six years. That the workers of the Myrmicinse 

 are almost or quite as long-lived may be inferred from the fact that 

 Miss Fielde has kept those of A. fnha under observation for a period 

 of three years. But even greater than the longevity of the worker is 

 that of the female, as would be expected from the larger size and 

 vigor of this caste. Janet ( 1904, p. 42-45 ) records the age of a 

 female Lasius alien us as fully ten years, and Lubbock kept a female 

 F. fusca alive from December, 1874, till August, 1888, " when she 

 must have been nearly fifteen years old, and, of course, may have 

 been more. She attained, therefore, by far the greatest age of any 

 insect on record." 



Closely related to the longevity of adult ants is the question of 

 their resistance to adverse conditions. On this subject, which is of 

 considerable importance in connection with the economic treatment 

 of these insects, Miss Fielde has published (1901 to 1905) a number 

 of interesting and painstaking observations. Although the optimum 

 temperature for our northern ants lies between 70 and 80 F., the 

 minimum and maximum to which they can be subjected and still sur- 

 vive, are very widely separated. Miss Fielde froze females, workers 

 and a brood of A plnenogaster fuk'a for twenty-four hours at - -5 C. 

 (23 F.). The insects were then gradually thawed and all survived. 

 Even the frozen eggs, larvae and pupse subsequently developed in a 

 normal manner. When the temperature was raised to 30 C. (86 F. ) 

 the ants began to- show signs of discomfort, at 35 C. (96 F. ) the 

 smallest individuals swooned, and even the most vigorous ants with 

 which she experimented succumbed after two minutes' exposure to 

 50 C. (122 F.). It has been known for some time that female ants 

 can go without food for the greater part of the year while they are 

 founding their colonies. Miss Fielde has demonstrated that large 

 workers can fast for almost equally long periods. She succeeded in 

 keeping F. sitbscricca and Camponotus americanus workers alive with- 

 out food for from 7 to 9 months. Ants are also able to endure long 

 submergence in cool or cold water. Miss Fielde found that Lasius 

 latipes survived 27 hours of this treatment; C. pennsylvanicus, 70 

 hours, and Aphcenogaster fitli'a eight days! This explains how ants 

 that sometimes nest in the beds of streams, like the Texan Pogonomyr- 



