Dr. G. B. Longstaff's Bionomic Notes on Butterjlies. 653 



the length of the shadow until the list amounts to 40' 

 (under the conditions assumed) and so brings the wings 

 into a position normal to the sun's rays. (See diagram C.) 

 The length of the shadow is then at its maximum and 

 longer than the wings. 



A further list will diminish the shadow until when 

 the wings touch the ground it will equal their length. 



A little consideration will, however, show that by listing 

 the butterfly, so to say, covers up its own shadow more and 

 more, so that while a slight list produces little effect on 

 the shadow, a considerable list — 45° and upwards — makes 

 the shadow less conspicuous than that cast by the same 

 butterfly in the upright position. 



My conclusion accordingly is that, so far as regards the 

 shadow cast, no list/yow the sun can be protective to the 

 insect unless it be extreme. Again, a list fo^om the sun, 

 by resulting in the maximum illumination of the wing 

 surface, can hardly aid concealment. At the same time, it 

 cannot be denied that a butterfly by placing itself out of 

 the upright, may thereby be protected in so far as it may 

 then be more difiicult to detach it from its surround- 

 ings. This would certainly appear to have been the case 

 with the Ilelanitis recorded by Col. Bingham* and by 

 " E. H. A," t also with the S. semele observed by Mr. E. G. 

 Waddilove. 



Dr. Chapman tells me that he has observed a marked 

 list in a Spanish species of Erebia, and my own experience 

 of list is confined to the Satyrines, a group of feeble fliers, 

 be it noted, with (at any rate in the great majority of 

 species) cryptic under-sides. I am, however, aware that 

 Prof. Poulton and Mr. Rowland-Brown have observed an 

 extreme list in Thecla ruhi, Linn, ; possibly connected with 

 the green colour of the under-surface of its wings. J 



Barrett's remark as to a rarer British butterfly, Graptct 

 c-alhum, Linn., deserves quotation : — 



"... fond of sunning itself in roads, on warm 

 walls, or on the ground upon dead leaves in sheltered 

 valleys. Here if the sun becomes overclouded, it will 

 sometimes close its wings and almost lie down, in 

 such a manner that, to distinguish its brown and 



* Trans. Ent. Soc. Lond., 1902, p. 363. See also " Butterflies of 

 India," vol. i, p. 47. f " A Naturalist on the Prowl," p. 203. 



X Proc. Ent. Soc. Lond., 1906, p. xxviii. 



