Feb., 1908.] Effects of Freezing on Insect Larvae. 259 



15th, -6 on the 16th, -17 on the l"^th, -6 on the 18th, -14 on the 

 19th, and -16 on the 20th. None of the specimens showed signs 

 of injury from the treatment. 



Three other larvae taken on the 14th, and treated exactly as 

 the above except that water was not used received no noticeable 

 injury. 



Three larvae taken on the 14th, and frozen in water and kept 

 at outdoor temperature for a week fully revived when thawed 

 out again. 



Larvae collected just after daylight on January 20, when the 

 thermometer registered -15 could be snapped in two almost like 

 icicles and crystals of ice were observed within their body 

 cavities. Some of these pieces were alive when thawed out at the 

 end of a week. 



Under natural conditions the larvae were to be found wher- 

 ever they happened to be when freezing temperature caught 

 them. Some in the centers of the reeds, some protected by onty 

 one or two thin leaf-sheaths, some at distances above the snow 

 ranging from an inch or two up to two feet, or even more, and 

 some beneath the surface of the ground near the roots of the 

 plants. 



In order to bring out a striking difference in results I wish to 

 give my observations on the larvae of the common Hawk-moths 

 of the tomato, two species of which are about equally common in 

 the state. During the Fall of 1896 these larvae were abundant 

 on tomatoes and when time for the first frosts arrived not all the 

 specimens had reached the mature larval condition and entered 

 the ground for pupation. Larvae of different sizes therefore 

 were observed feeding actively on the tomato vines the day 

 before the first frost came. The frost was not a hard one but the 

 exposed parts of the vines were killed as were the larvae on these 

 parts. Larvae on the parts of the vines that were not killed 

 kept on feeding the following day, but a frost the next night 

 killed most of the leaves that had escaped the previous night and 

 with them the remaining larvae. 



Previous to 1903, for several years canker worms were abun- 

 dant on the elm trees along the river on the Ohio State University 

 farm. During April of 1903 the warm weather hatched the eggs 

 of the Fall Canker-worm and the larvae started in to cause havoc 

 among the elm leaves, but a frost on May 4, killed so many of 

 them that they have not been a serious pest since. It may be 

 stated that A. F. Burgess made a similar observation in regard 

 to the Spring Canker-worm on apple the same Spring, and those 

 who have observed know that the latter species has not done the 

 damage since 1903 that it did the few years previous to that year. 



