654 Dr. G. B. Longstaff's Bionomic Notes on Butterflies. 



green marbled underside from the dead leaves is 

 almost impossible." * Here Barrett says if the sun 

 becomes overclouded, but I have observed the list 

 during bright sunshine only. 



When my attention was first drawn to the subject of 

 Heliotropism by observing the habits of Pararge schakra, 

 Koll., in the Simla district in October, 1903, I was dis- 

 posed to associate that habit with another — that of listing 

 to one side or the other — and suggested that both had 

 probably been selected since they appeared to assist to a 

 notable degree in the concealment of the insect from its 

 foes.f 



The evidence now available is more ample though still 

 far short of what would be requisite in my opinion to 

 establish definitely any explanation. 



Prof. Parker's explanation that by negative Heliotrop- 

 ism the insect displays its colouring to the best advan- 

 tage, can scarcely be applied to list, for while it may be 

 true tliat by listing a butterfly displays its under-side, that 

 under-side is in listing butterflies usually cryptic, even 

 when in our cabinet it appears the more brilliant of the 

 two. Moreover, in the listing position the most con- 

 spicuous feature of the pattern is often concealed by the 

 hind-wing. 



That under special circumstances there is an " economy 

 of shadow " in both heliotropic and listing butterflies is 

 unquestionable. On the other hand, the negatively 

 heliotropic butterfly with wings expanded, and the listing 

 butterfly with wings closed, both place their wings as 

 nearly as may be normal to the sun's rays, exposing in 

 the one case their upper, in the other their under, surface. 

 Is it possible that the direct rays of the sun falling 

 normally on either surface of the wings, afford a pleasur- 

 able sensation to the insect ? Or is the exposure of the 

 insect's hod// to the sun, common to some extent to both 

 these attitudes, the end obtained ? The obvious love of 

 most butterflies for hot and sunny corners unquestion- 



* Op. cit. p. 125. 



t Mr. Marshall writes to me that he has observed in the case of 

 three S. African butterflies, Precis cehrene and Eamanumida 

 daedulus, at Salisbury, and Myculesis mmpina, Auriv., in Chirinda 

 forest, that when they have been sunning themselves they have 

 closed their wings with a snap when a heavy cloud has passed over 

 the sun. 



