652 Dr. G. B. Loi^taff's Bionomic Notes on Butterflies. 



If the butterfly were to list towards the sun its shadow, 

 still fully exposed to view, would diminish until the list 

 were equal to the sun's altitude, when there would be no 

 shadow. In this position, moreover, its wiog surfaces 

 would be least illuminated. 



Diagram B. 



Butterfly listing, more than 60° townrds the sun. 



Supposing the butterfly to increase its list ; this would 

 bring the sun's rays on to the under surface of its left 

 wings and so throw the shadow to the right, or towards 

 the sun. (See diagram B.) The shadow would continue to 



Diagram C. 



Butterfly listing, 40° from the sun. 



increase in length until when the butterfly's wings touched 

 the ground it would equal them in length. On the other 

 hand, as the shadow increased in length it would be more 

 and more concealed from view. 



But as a matter of fact the list has almost always been 

 observed to be away from the sun. Such a list increases 



