81 



iialing caterpillars. Adult hces were found to die when 

 their temperature was lowered to -0.7°. 



Robinson (1926) insisted on the importance of the time 

 factor in death by cold. For exposures of Sifophilus 

 oryzae to temperatures from 1.1° to -17.70°, he obtained 

 lethal times decreasing from 98 to 1^^ hours. As to the 

 cause of cold hardiness, Robinson seeks it in the amount 

 of bound water, and the hardening- process would consist 

 in increasing water-binding. 



According to Kalabuchov (1934), bees, humhle-'bees, 

 wasps, and larvae of beetles can revive after having been 

 subcooled for 48 hours at temperatures from -2.9° to 

 - 17.1° (body temperatures). Death usually ensues a few 

 minutes after the beginning of ice formation subsequent 

 to subcooling. Partial freezing, without preliminary sub- 

 cooling, is not fatal, nor is partial freezing following a 

 slight subcooling of short duration. Complete freezing 

 is always lethal. 



Results, similar to those reported by Duval and Portier 

 and by Payne, were obtained by Lozina-Lozinskij (1935) 

 on the caterpiUars of a Pyrausta. These animals, frozen 

 at -21°, and breakable like glass, were revived after a 

 stay of 8 days in the congealed state. Considerable 

 changes in the position of the freezing point and in the 

 cold resistance took place during the passage from one 

 metamorphosic stage to the other. 



Kapterev (1936) says that he "often" revived cy clops 

 taken from layers of ice 3 to 12 cm. thick. But, what is 

 much more remarkable, is the experiment in which he 

 claims that he revived a crustacean, Chydorus sphericus, 

 isolated from a piece of soil taken in the permanently 

 frozen ground, at a depth of 3.5 meters, in the valley of 

 the Great Never River (a tributary of the Amur). He 

 thinks that the "age of the layers whence these samples 

 were taken should be reckoned not in hundreds but in 

 thousands of years." 



Some investigators have reported injurious effects or 

 death as a result of long exposures of insects to tempera- 

 tures above zero. For references, see Uvarov (1931). 



