THE CANADIAN ENTOMOLOGIST 



POPULAR AND PRACTICAL ENTOMOLOGY. 

 Heliotropism in Butterflies; or, Turning Towards the Sun, 



HV ALHERT F. WINN, WESTMOUNT, QUE. 



These who have read Dr. G. B. Longstaff's book, "Butterfly 

 Hunting in Many Lands," have enjoyed his accounts of the peculiar 

 habit that some species of butterflies have of carefully adjusting 

 themselves to a certain position when they settle. Most of us will 

 recall similar instances, such as our common Sulphur, Colias 

 philodice, which is often seen in great numbers near puddles of rain 

 water along country roads, resting with the wings closed over the 

 back frequently leaning over at an angle of 45° to even 30° to the 

 ground; or the Vanessas and Graptas alighting on a fence or tree 

 trunk only to immediately shift the position of the body to one 

 perhaps at right angles to what it had been or even exactly reversing 

 the direction in which the head pointed. But until attention was 

 called to it as a phenomenon of which an explanation was desired, 

 it has been generally passed by as being an everyday occurrence, 

 without any effort being made to try to find out why the insect 

 should act so, or to keep accurate notes on exactly What the re- 

 spective positions were, as well as the position of the sun, direction 

 of the wind, temperature and nature of the object settled on. 



A theory of Dr. Longstaff is, that in assuming a position in- 

 clined sideways the butterflies more easily escape detection, as the 

 shadow is reduced to a minimum. This may be the true explana- 

 tion in the case of the insects which Dr. Longstaff has seen and studied 

 in his extensive travels, and we do not wish to imply or express 

 the slightest doubt on his interesting conclusions, but only to call 

 attention to a subject that has been little written about in the life- 

 histories and habits of our Canadian butterflies, and careful observa- 

 tions may prove valuable as well as being interesting to the student 

 of nature. 



So far as Colias philodice is concerned, this orientation, as it is 

 termed, was referred to in an article in one of the early volumes of 

 this journal by Wm. Couper — "A Dissertation on Northern Butter- 

 flies" (V'ol. VI, p. 92). He says: "When it alights on a flower, 

 instead of being erect on its feet, it lies sideways, as if to receive 

 the warmth of the sun." The same idea has been maintained by 



January, 1916. 



