244 THE entomologist's record. 



rest at short intervals for recuperation, which we call sleep ; but Mr. 

 Tutt appears to be alluding to a resting-state analogous to hyberna- 

 tion, which is not a physiological necessity. If we are to look for 

 some predisposing cause, some "capacity for assuming a resting 

 state," may we not find it in the quiescence of the larva after each 

 moult ? The prolonged inactivity of the pupa after the final moult 

 is necessitated so as to allow important changes to take place as to 

 mouth, muscles, wings, assimilative, nervous and reproductive 

 systems. In a minor degree a similar inactivity exists for a longer or 

 shorter space of time after each moult, during which the new external 

 tissues get hardened. May not this help to explain the occurrence of 

 hybernation at some definitive moult only, varying in dift'erent species, 

 as described by Mr. Tutt and others ? 



For my own part, whilst agreeing with Mr. Kane in considering 

 hybernation, " a suitable adaptation," and that its " unreasonable 

 survival " explains many of Mr. Tutt's anomalous instances, I cannot 

 attribute it in all cases to cold alone ; but, when induced in the larva, 

 think it due, as Mr. Tutt does, to insufficiency or absence of food as 

 a primary cause, and cold as a secondary one, whilst admitting the 

 all-etficiency of cold in the hybernation of the imago. 



Mr. Kane seems to imply, if I do not misunderstand him, that 

 hybernation may be only torpidity ; but, surely, it is something more. 

 We all agree that torpidity may l)e a result of cold, but how can this 

 explain a larva providing a shelter for itself before cold has set in — 

 the old argument against it ? Though many larva? simply hid,e 

 themselves in any suitable hole, under stones, leaves, moss, etc., 

 others line their cavities with silk, and never emerge till their 

 food is ready for them to commence feeding again. Larva? are 

 imperfect insects, and their hybernation does not run on a line with 

 that of the imago. They have no reproductive system (or only rudi- 

 mentary elements), and their life's object is nutrition to such an 

 amount as is necessary for the subsequent formation of the perfect 

 insect. Their capacity for nourishment is many times that of the 

 imago. If this be the case, is it not probable that the absence of 

 food will react sooner than any other cause ? Most vegetation dies 

 oflf at the approach of winter, and may not a scarcity of food induce 

 sensations in the larva, warning it to provide winter quarters '? Larvre 

 can stand a great amount of cold ; they can be frozen and yet retain 

 their vitality, and we are repeatedly seeing them surviving the 

 severest winter, but starvation plus cold (the larva not having 

 hybernated) is fatal. Do we not meet with this throughoiit all 

 nature '? Birds die during severe winters, mostly not of cold, but of 

 starvation plus cold ; and so it is with ourselves, we can resist extreme 

 cold provided there is a sufficient food supply. Is it not probable, 

 then, that scarcity of food warns the larva to seek winter quarters, 

 and increasing cold gradually induces torpidity, a torpidity, let us 

 remember, not variable so as to allow of activity during milder 

 winters, but persistent in true hybernation till the warm spring sets 

 in and food-plants are ready to supply nourishment ? Kirby and 

 Spence, in support of this, quote Reaumur's instance of the larva? of 

 Melitaea cinxia and J'orthesia c/in/sarrhuea, the former coming out of 

 winter quarters a month earlier than the latter, because they are 

 grass or plantain, and the others, arboreal, feeders. The same occurs 



