HIBERNATION AND SLOUGHING. 61 



when that cold is very far short of the winter tem- 

 perature. I have often noticed, when snake-hunting 

 in the Monnow Valley, how a change of wind affects 

 the adders. Let a cold east wind strike the slopes 

 of Garway Hill or the Graig, and the adders which 

 yesterday were lying out on the margin of the cut 

 bracken, or on the paths through the woods, are no- 

 where to be seen. Even the snakiest spots, where one 

 knows the reptiles are, will be searched in vain on a 

 cold day. So repeatedly have I found this to be the 

 case, that now I never go to certain favourite hunting- 

 grounds unless I see that the wind is from a warm 

 quarter. Thus it is that the time of the retirement 

 for the winter varies considerably with the particular 

 season : one year all the snakes will have disappeared 

 by the middle of September, whilst in a warm late 

 autumn they will be found active towards the end 

 of October. In the same way the date of commenc- 

 ing activity in the spring is found to vary according 

 as that season is early or late. F. G. Aflalo ^ mentions 

 that he has " found adders lively in the New Forest in 

 the middle of April, rarely before ; but Sir Herbert 

 Maxwell tells me that he has seen them in Scotland as 

 early as March." In Dorset they are generally seen 

 in February. Of course it is difficult to be quite cer- 

 tain as to the exact date, because the snakes may have 

 been moving about in any given district some weeks 

 before any one happened to see one. 



^ Natural History (Vertebrates) of the British Islands, p. 305. 



