ABOUT CHRYSALIDS 239 



invariably make their appearance before the fe- 

 males, sometimes only a day or two, sometimes as 

 many weeks. It seems only another instance, so 

 many of which are known in both animal and veg- 

 etable kingdoms, of a device to secure fertilization. 

 Now, Mr. Edwards, with his unrivaled experience 

 in breeding butterflies, tells us, what all of us have 

 seen on a smaller scale, that when bred in confine- 

 ment, not exposed to all the vicissitudes of the 

 weather, the females appear quite as early as the 

 males. What subtle influence then is it which 

 earlier awakes the male under wholly natural con- 

 ditions ? 



We owe to Wilhelm Miiller (a brother of Fritz 

 Miiller, who has made so many neat observations 

 in the natural history of tropical animals) a curi- 

 ous fact in the lives of the free hanging chrysalids 

 of tropical Nymphalidae. Every naturalist knows 

 how rarely these chrysalids are discovered in free 

 nature ; most of our knowledge of them comes 

 from those raised in confinement ; for the cater- 

 pillar nearly always seeks an obscure place in 

 which to change, or else imitates in its color and 

 perchance in its form, surrounding objects. Now 

 Miiller has discovered that many of them are 

 directly sensitive to light and will respond, slowly 



