EEVIEWS AND NOTICES OF BOOKS. 117 



again with a delight equal to that we enjoyed at our first acquaintance. 

 The 31 chapters are culled from the author's great work, Buttcrjlies 

 of the Kaxtern UniU'd States and Canada, and deal with the more 

 philosophical questions that arise in the mind of every thoughtful 

 entomological student. They have been revised, and are now quite 

 up to date, and include extensions in the direction of some of the more 

 recent discoveries such as those with regard to the coloration of certain 

 larvre and pupfe, by means of which they assimilate to their environ- 

 ment, and other additions of equally recent date. To quote from it would 

 be to steal the book, for where should we leave oft' once the quoting 

 commenced ? In view, however, of the papers on hybernation, 

 recently published in this magazine, we would give the following 

 extract from the chapter, " Lethargy in caterpillars." The author 

 writes : — " There are lethargic periods in the life of every caterpillar, 

 when it has gorged itself to the full, and rests quietly to digest its 

 meal ; but these last at most but a few hours. For those that feed 

 exclusively by day, or by night, as the case may be, there is also that 

 slightly longer diurnal period when 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 must pass the winter in the caterpillar stage, a period we 

 call hybernation, 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 midsummer, when the food-plant of 

 the caterpillar is superabundant and low temperatures are at farthest 

 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 in the regular course. Even 

 the portion which is concerned in it may be unequally aftected, 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. The same phenomenon occurs in the chrysalis state, 

 where sometimes early in the season a portion of a brood will disclose 

 the butterfly, while another portion will retain the inmates until the 

 succeeding spring, etc. But its occurrence in the active larval stage 

 is far more unexpected. 



" This lethargy in caterpillars was first observed by a French natur- 

 alist, named Vaudouer, more than sixty years ago, but his statements 

 lay a long while nearly unnoticed. According to this observer (a full 

 account of whose observations is given in my Netr Knriland Butterfiies), 

 one of the European species of Brenthis, upon wliich he experimented 

 flies in May, and again in July and August. The caterpillars from 

 the second summer brood are half-grown when winter comes, hyber- 

 nate in this stage, and, in time, produce the spring brood ; the 

 caterpillars of the spring brood, when they have reached the hybernating 

 age, late in June, act in a precisely similar manner, and some of them 

 do not arouse until the succeeding spring, when, with the caterpillars 

 of the summer brood, they produce a new spring brood, but other 



