HIBERNATION OF ANIMALS. 135 



mostly hollow, although some of them contain tracheae. One pe- 

 culiarity of this insect is the fact that its wings are reversed, that 

 is to say the wing coverts are folded in under the wings, which as 

 the insects reach maturity, gradually change about and the wing cov- 

 erts, become hard and form a protection, to the true wings, which in 

 turn become quite delicate. 



The abdomen of the female is longer than that of the male. 

 The first eight rings can be easily counted, but the ninth and tenth are 

 fused together. On each side of the abdomen the skin is turned inward, 

 forming a longitudinal fold which separates the upper part of the ring 

 from the lower; just above this fold, on either side, are the breathing 

 holes, or spiracles. Each spiracle is a slit-like opening surrounded by 

 a horny ring, and is situated on the anterior portion of the segment. 



Fig. 20. 



Milbert's butterfly, Vanessa milberti. A butterfly which hibernates. 



HIBERNATION OF ANIMALS. 



BV 



C. J. Maynard. 



Although the term to hibernate, according to the dictionaries, is 

 applied to animals which pass the winter in close quarters, whether 

 they remain dormant or not, such is not the sense of the term usu- 

 ally understood by Zoologists. 



The term hibernation should be applied only to such animals as 

 pass the winter in a dormant (lethargic) state and without taking food. 

 In m:my cises, probably always among vertebrates, there is a quantity 



