INTRODUCTION 37 



Various explanations of this phenomenon have been 

 offered but apparently none of them are yet generally 

 accepted. Were the habit confined to butterflies like the 

 Mourning Cloak, it would seem easy to prove that a main 

 advantage was found in the benefit derived from the heat 

 rays of the sun. Were it confined to those species which 

 always fold their wings on alighting, it would seem easy to 

 beheve that it was a device for reducing the shadow cast by 

 the insect to its lowest terms. It has also been suggested 

 that the habit is for the purpose of revealing to the fullest 

 extent the markings of the butterfly. Evidently there is 

 here an ample field for further investigation before definite 

 conclusions are reached. 



List and Shadow Observations 



Another field for most interesting studies upon the 

 habits of living butterflies has been opened up by the very 

 interesting discussion of list and shadow in Colonel G. B. 

 Longstaff's fascinating book, "Butterfly Hunting in Many 

 Lands." He there summarizes his numerous observations 

 upon butterflies in various localities which he has seen to 

 lean over at a decided angle when they alight. He de- 

 fines '^Lisf as "an attitude resulting from the rotation 

 of the insect about its longitudinal axis, as heliotropism re- 

 sults from a rotation about an imaginary vertical axis at 

 right angles to this." The name is adapted from the 

 sailors' term applied to a vessel leaning to one side or an- 

 other in a storm. 



Apparently this interesting habit was first called to the 

 attention of European entomologists by an observation of 



