328 



THE GYPSY MOTH. 



and the various molts up to and including the fourth. 

 When taken from the oven, all but one were dead. 



Effect of Cold. — Ten caterpillars just hatched, also ten 

 from each molt up to the fourth, were selected and placed in 

 vials, after which they were subjected to a temperature of 

 85° for a period of five minutes. They were then placed in 

 a cold box, where they were exposed to a temperature of 2^ 

 above zero for a period of thirty minutes, at the end of which 

 time they were removed to a room where the temperature 

 was 70*^, and examined. Only one caterpillar survived the 

 above treatment, but this one, after a few days, fed and grew 

 in a normal manner. Fifty caterpillars, in lots of ten, from 

 the difierent molts, were transferred from a normal tempera- 

 ture of 70° and exposed to a temperature of zero for a period 

 of half an hour, when they were returned to the tempera- 

 ture from which they were first taken. When removed, all 

 were dead. Fifty caterpillars in the various molts, up to 

 and including the fourth, were placed in vials (the mouths 

 of which were stopped with cloth instead of cork), and then 

 removed from a temperature of 82° to a cold box, where 

 they remained fourteen hours, exposed to an approximate 

 temperature of zero. All were dead when taken out. 



A study of these experiments shows that, as a rule, the 

 small caterpillars possess the ability to resist a considerable 

 degree of cold but not of heat ; while the larger caterpil- 

 lars possess the ability to resist the heat better than the 

 cold. This is as one would naturally expect to find it, 

 since at the time of hatching the weather is usually cool, 

 while the increase in size of the caterpillars keeps pace 

 with the ordinary increase of temperature, so that by the 

 time the caterpillars are full grown we often have a con- 

 siderable degree of heat. 



Experiment in droioning Cateiyillars. 

 In many places the gypsy moth infests the trees along the 

 course of streams, under such circumstances as to lead to 

 the impression that they were distributed by falling into 

 the water while in the caterpillar stage, and, drifting down 

 stream with the current, reached the shore, and, making 



