THE .ESTIVATION AND HYBEENATION OP BUTTERFLY LARVM. 7 



e.g., Erebia aethiops, Aricia astrarche, Chrysophanus dispar, etc., and 

 then fall into a state of greater or less torpidity, from which they will 

 not stir till the following spring, although, at the time, surrounded by 

 an abundance of food, and apparently suitable temperature, etc. This 

 summer or aestival rest, Scudder, under some misapprehension as to 

 the details relating to certain partially double-brooded species, terms 

 " lethargy." He writes (p. 551) : " The period of inactivity termed 

 lethargy is directly connected with hybernation, although neither of 

 the provocative causes (low temperature and absence of food) 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 midsummer, when the foodplant of the caterpillar 

 is superabundant and low temperatures are at furthest remove. In 

 some instances, it extends from midsummer to winter, and so may be 

 called premature hybernation. In nearly, if not quite, all cases, it 

 affects only a portion of any given brood of caterpillars, the remainder 

 of the brood continuing on its 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 hybernation .... 

 This lethargy was first observed by a French naturalist named 

 Vandouer, some sixty years ago." Vandouer's remarks, here referred to, 

 are based on certain observations recorded in the Mem. Soc. Linn. Paris, 

 vi., pp. 374-8. He observed that, in May, 1819, a .? Brerithis euphro- 

 syne laid eggs which produced, in 10-12 da} r s, larvae 2mm. long, that fed 

 on violet leaves until after the third moult, when they ceased eating and 

 attached themselves to the sides of the breeding-cage. Food, sun, air, 

 disturbance, failed to make them more than move their position and 

 fall again into a lethargic state, when after a month, disgusted with 

 what he considered his want of success, Vandouer threw them away, 

 believing that they required natural conditions for success ; but, in 

 early September, 1825, larvae of B. clia hatched, and these, at the end 

 of October, hid themselves in dry leaves, etc., as the larvae of B. 

 euphrosyne had done, and then Vandouer understood that he had made 

 a mistake, due to the fact that he had not conceived it possible that 

 any larvae could become lethargic or " marmotic " at the beginning of 

 summer, especially as B. euphrosyne was, in his district, on the wing 

 twice in the year, viz., May and July-August. So, in May, 1826, he 

 again obtained larvae of B. euphrosyne, which stopped eating at the 

 end of June, except a few, which fed sparingly through July, and 

 became pupae and butterflies in August. The rest of the larvae, 

 however, continued their primitive aestival torpor until February 26th, 

 1827, when they began to move, but partook of no food till the 

 temperature was somewhat higher ; then they grew slowly, moulted 

 twice, and finally completed their metamorphosis between April 7th 

 and May 10th. At the same time, Vandouer, on July 27th, 1826, 

 had obtained eggs from a second-brood $ of B. euphrosyne. These 

 produced larvae, which moulted three times, and then became torpid, 

 as in the case of the May- June larvae, going over the winter 1826-7 with 

 them, and in the same larval stage. These also awakened on 

 February 26th, 1827, at the same time as the larvae which had 

 remained concealed in dry leaves since the close of June, 1826; in 



