LF/rilAlUlY IN CATEKPILLAKS. 551 



color, often with longitiuliniil (Lirkcr or paler dorsal and lateral l)ands. 

 Tiieir movenients are exceptionally rapid, like tliosc of tlie swift-travelling 

 Arctians. 



The chrvsalids arc ifiassive, more or less angulate, constricted across the 

 back, the ocellar tubercles only moderately prominent, the thorax keeled 

 and arched, the wing cases ample and protuberant, the abdominal seg- 

 ments furnished on the back with laterodorsal roAvs of tubercles ; they are 

 generally brown, often furnished with golden or silvery spots, especially 

 on the tubercles. 



EXCURSUS XVIL— LETHARGY IN CATERPILLARS. ' 



The caterpillar on the leaf 

 Repeats to thee thy mother's grief. 

 Kill not the moth nor l)iittertly, 

 For the last judgment draweth nigh. 



Elake. — Aufjuries of Innocence. 



One of the most inexplicable phenomena in the life-history of butterflies 

 is the fact that during the only period of activity in the preparatory stages, 

 a period when all the energies seem to be concentrated on eating and 

 growing, there should occasionally intervene a lethargic period when all 

 activities are suspended, the creature partakes of no nourishment, moves 

 at most only by its own length to secure a position more to its liking, as a 

 drowsy sleeper turns in bed, and that this period should last for weeks or 

 even months. 



There are lethargic periods in the life of every caterpillar, Avlieu it has 

 gorged itself to the full and rests quietly to digest its meal ; but these last 

 at most but an hour or two. For those that feed exclusively by day, or 

 by night, as the case may be, there is also that slightly longer diurnal 

 period Avhen they enjoy a period of quiet shared with a great body of their 

 fellow creatures, including ourselves. There is further that much longer 

 period of inactivity which comes to those that mnst pass the winter in the 

 caterpillar stage, a period we call hibernation, and Avhich 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 midsunnner, when the food-plant of the caterpillar is superabundant and 

 hjw temperatures are at farthest remove. In some instances it extends 

 from midsummer to winter and so may be called premature hibernation. 

 In nearly, if not quite, all cases it aflfects only a portion of any given brood 

 of caterpillars, the remainder of the brood continuing on in the regular 



