Feb., 1908.] Effects of Freezing on Insect Larvae. 
2 59 
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 only 
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. 
