1/2 A. M. FJELDE. 



light or when in pursuit of scattered larvae which are commonly 

 sought with self-sacrificing assiduity. 



When the largest ants were introduced into the rest where the 

 temperature was between 40 C. and 50 C. or 105 F. and 

 122 F. they either succumbed to the heat and swooned upon 

 the floor or else struggled away toward the cooler end of the 

 nest. All ants that swooned and fell where the temperature was 

 below 50 C. recovered their activity if soon removed to cool 

 and humid quarters. Ants exposed for two minutes to a tem- 

 perature of 49 C. revived after some hours and resumed their 

 normal occupations. 



But exposure to heat so great as 50 C. or 122 F. produces 

 in the ant pathological conditions from which it does not recover 

 if the exposure is sufficiently prolonged. Probably the proto- 

 plasm of the ant coagulates at 50 C., the time required for the 

 coagulation of all the protoplasm depending on the size of the 

 ant. The time is the same for ants of the same size and species, 

 whether the heat be imparted through a dry or a wet medium. 



In order to ascertain the time required for the heat to kill the 

 ants, I adopted a method which produced no mechanical injury. 

 Grasping one or more legs of the ant with padded forceps, I 

 merged the ant in air or water heated to just 50 C. and held it 

 there for the recorded number of seconds, then laid it upon a 

 cool moist sponge, to remain under observation during the five 

 ensuing days or longer. Every ant appeared to die as soon as 

 it reached the heated medium. 



The first sign of revival, a slight twitching of the legs, was 

 sometimes given many hours or even a day or two after the ex- 

 posure to the heat. That these throes were those of returning 

 rather than of departing life was proven by the complete recovery 

 of some of the ants after days of manifest illness, abstentation 

 from food and indifference to environment. Many ants revived 

 that never wholly recovered. 



Whenever any ant gave evidence of life, I provided hygienic 

 conditions and trained nursing. Recuperation was slow in pro- 

 portion to the length of time the ant had been exposed to the 

 heat. One Stenamnia that had been exposed twenty seconds, 

 gave the first sign of returning life forty-seven hours later, and 



