LETHARGY 227 



selves. There is further that much longer period 

 of inactivity which comes to those that must pass 

 the winter in the caterpillar stage, a period we 

 call hibernation, and which is immediately related 

 to low temperature and absence of food. 



The period of inactivity termed lethargy is 

 directly connected with this last, although neither 

 of the provocative causes are present. It is a 

 period of greater or less duration, lasting from 

 a few days to a few months, generally as much as 

 two or three weeks, often in the very heat of mid- 

 summer, when the food-plant of the caterpillar is 

 superabundant and low temperatures are at far- 

 thest remove. In some instances it extends from 

 midsummer to winter and so may be called pre- 

 mature hibernation. In nearly, if not quite, all 

 cases it affects only a portion of any given brood 

 of caterpillars, the remainder of the brood contin- 

 uing on in the regular course. Even the portion 

 which is concerned in it may be unequally affected, 

 some arousing from the torpor at the end of a few 

 weeks and proceeding regularly thereafter with 

 their transformations, others continuing torpid to 

 and through the winter. This shows its direct 

 relation to hibernation. The same phenomenon 

 occurs in the chrysalis state, where sometimes 



