176 AROMATIC BUTTERFLIES 



smell ; each consists of a sac-like cavity, the open- 

 ing into which is often protected by cuticular pro- 

 cesses, and at the bottom of which in the hypoderm 

 is situated a fusiform body with a delicate conical 

 ending extended free into the centre of the sac, its 

 other extremity being in direct continuation of a 

 nervous thread. 



For myself I am inclined to attribute to butter- 

 flies, as to moths, an exceedingly delicate and high 

 perception of odors. Any one observing their action 

 with this in view will find numerous instances in 

 which this sense certainly seems to come in play, 

 particularly as it appears highly probable from re- 

 cent researches that the sight of these creatures is 

 far less distinct than was formerly supposed. The 

 mere fact that the eggs of butterflies are invariably 

 laid upon or in close proximity to the food plant of 

 the caterpillar can be explained, as I have already 

 suggested, only on the supposition that the crea- 

 tures have the power of distinguishing such plants 

 by their odors. If one will watch a butterfly bent 

 upon laying eggs as it flits in and out among the 

 herbage, he cannot fail to perceive the brief visit 

 it makes to plants which seem quite closely to re- 

 semble the food j)lant of the caterpillar, and how 

 quickly it settles upon the desired object, as if it 



