Doeiihoir (1S72) placed hees, spiders and tucat flies on 

 the frozen ground, covered them with a wire cage, and 

 exposed them thus for 5 hours to a temperature of - 1.5°, 

 as indicated by a thermometer laid on the ground. The 

 bees were killed by this treatment, but the spiders and flies 

 soon recovered. It took an 8-hour exposure to - 2° to - 3° 

 under similar conditions to kill the spiders, while the flies 

 survived even a 12-hour exposure to -3.75° to -6.25°. 

 The flies were then put into a small glass, 1^ inches long 

 and ^l inch wide and so immersed into an ice-salt mixture 

 at -3.5° to -6.5° for 4 hours. They survived this treat- 

 ment also. Finally, they were killed by a 3-liour exposure 

 to -6° to -10°. 



Plateau (1872) studied the cold resistance of aquatic 

 arthropod a. They were placed in glass tubes containing 

 a few cc. of water and a thermometer, and the whole was 

 immersed in a cooling mixture. The animals were little 

 by little surrounded by ice, and finally caught in it. 

 Plateau measured the time during which they were caught 

 in the ice and recorded their survival after thawing. He 

 gives the following figures as the longest periods sup- 

 ported in ice : 10 to 30 minutes for 3 coleoptera, 2 to 10 

 minutes for 2 liemiptera, 20 to 30 minutes for the larva 

 of a neuropteron, 2 minutes for the larva of an ortJiop- 

 terou, 10 minutes for the crustacean, Asellus, 1^ minutes 

 for Daphuia and 1 minute for Cyclops. In experiments 

 conducted in sugar solutions which froze at -2°, Asellus 

 always died in less than a minute after it was caught in 

 the ice, but it did not die at - 2° when no ice was present. 

 For Plateau it is evident, that the aquatic insects die at the 

 temperatures at which ice forms in the fluid medium 

 around them. 



Roedel (1886) made experimental determinations of the 

 death temperature of some arthropoda with an apparatus 

 consisting of 2 concentric tubes, of which the external one 

 contained a freezing mixture and the internal one the 

 experimental animals, each tube being provided ^^dth a 

 thermometer. For slow cooling, he used the principle of 



