Dr. G. B. Longstaff's Bionomic Notes on Butterjlies. 651 



Mortehoe, 22 August, 1907. A $ observed to settle three 

 times, (1) oriented ; (2) across, with slight list away 

 from the sun ; (3) oriented. 

 August 24. A ^ settled on a leaf oriented. 



The effect of a list on the shadow, * 



It is worth while carefully considering the precise effect 

 of a list on the shadow of a butterfly sitting with the axis 

 of its body at right angles to the sun's rays. 



To make the matter clear I have constructed three 

 diagrams. The diagrammatic butterfly is in each case 



Diagram A. 



Butterfly upright, sun's elevation 50°. 



supposed to be settled with its tail towards the observer, 

 but turned somewhat to the left so as (in two of the three 

 diagrams) to expose the underside of the right wings 

 obliquely to the observer. The sun is supposed to be to 

 the right of the observer and nearly to the right of the 

 butterfly. The sun's elevation is taken to be 50°, repre- 

 senting a condition of affairs that is fulfilled in Europe 

 during some part of every day near midsummer, and in 

 the tropics during some part of every day in the year. 



When the butterfly is upright its shadow is nearly as 

 long as its wings, moreover its shadow is fully exposed to 

 view. (See diagram A.) 



