THE IlLBEllNATION OF CATERPILLARS. 689 



Pholisora, fully grown, partaking of no further nourishment when the 

 winter is passed, but changing to chrysalis almost or actually before their 

 food plant puts forth its leaves in the spring. Others still, and among 

 these are most Satyrinae and Argynnidi, winter as young larvae just 

 hatched from the egg, genei-ally, perhaps always in New England, before 

 they have touched a morsel of vegetable food, though their natural food- 

 plant, upon which they were born, still oiFers sufficiently tender leaves. 

 Of the species represented in this last category, some are not wdiolly 

 dependent upon the survival of these delicate creatures, but accompanying 

 them are half grown caterpillars of a preceding brood ; this is especially 

 the case with Brenthis. Of those that pass the winter half grown, we 

 may specify Cissia, Basilarchia, Brenthis, all New England Melitaeidi, 

 probably the species of Eurymus, and not improbably most of the Pam- 

 philidi, of whose complete transformations we know far too little. 



The most surprising fact we find here is the hibernation of young cater- 

 pillars just born. As they eat nothing, one would think they might at 

 least have had the protection of the egg-shell and wintered within the egg ; 

 but in the cases in point, Satyrinae and Argynnidi, the eggs are naturally 

 laid upon the leaves of plants which die down in the winter. Never- 

 theless it has been thought that in natural conditions, as has been known 

 to occur in artificial, the caterpillar may sometimes not emerge from 

 the egg until spring. I suspect that the caterpillars may be fully formed 

 in the case of those other butterflies which hibernate in the egg state, such 

 as some Theclidi and Chrysophanidi ; for with many of these the eggs 

 are laid in midsummer and the caterpillars do not emerge until early spring. 

 The occasional appearance in these species of an autumn butterfly, however j 

 indicates that in some exceptional instances an egg may hatch and the 

 caterpillar grow to maturity the same year. 



Hibernation at this tender age is all the more surprising from the fact, 

 known only too well to everyone who has attempted to raise buttei'flies 

 from the egg, that the greatest mortality exists among caterpiUars in the 

 first stage of existence, whether from natural causes or from the attacks of 

 enemies, and also because in no case do these apparently helpless little 

 creatures, generally but two or three millimetres long, construct any sort 

 of a nest or retreat for their common or individual protection. They 

 merely seek hiding places separately in curled leaves, in the ground, in 

 crevices of bark and similar spots, wdierethey are certainly not out of the way 

 of mites and ants. Neither have they any appendages which are not shared 

 with other juvenile caterpillars which do not hibernate. Yet there is no 

 evidence from any poverty of butterflies in these groups that they do not 

 retain as good a hold upon the fauna as those species which do not pass 

 what would seem to be so perilous a winter. On the contrary, our Saty- 

 rids and Argynnids are plenty enough on the wing. 



87 



