THE FAERY YEAR 



did not mention anything about the cause of this 

 and kindred states. Clearly animals, as a rule, are 

 thrown into these trances to escape not cold but 

 starvation. On first thought, the butterfly seems to 

 be an exception. It practically does not feed, so 

 starvation need not be guarded against is what 

 occurs to one. Yet if the butterfly were to retain 

 and exert its full vital energies when winter set in, 

 it would spend its tissue far more extravagantly than 

 it does in deep sleep. This would be a mere 

 squandering of vital energy, serving no purpose, 

 even if at the coming of winter the butterfly were 

 fat and strong enough to live on itself till the 

 following spring. 



With those warm-blooded animals that hiber- 

 nate completely as the dormouse the temperature 

 of the body is little higher than that of the air. 

 Their life functions are greatly depressed. It is 

 almost suspended animation. The pulse is reduced 

 to a tenth of the usual number of beats, breathing to 

 a thirtieth of the usual number of respirations. A 

 very little fuel is enough to keep so slow a fire 

 alight, and this is paid out by the surplus of fat 

 stored in the sleeper. It is the most economical life. 

 But there must be no going to sleep hungry and 

 thin, or the sleeper might not live to wake : it 

 would consume its meagre store of food, and the 

 fire of life would flicker out. 



I spoke about the brimstone butterflies feeding 

 freely at the close of summer, but the subject of 

 what provisions are taken by other hibernating 

 48 



