INTRODUCTION 23 



parently live through the winter to some extent, resting 

 beneath the bark of large branches or upon the trunks of 

 trees. Many of them also secrete themselves in hollow 

 trees or beneath loose bark or in board piles or stone walls. 

 It is probable, however, that during the long ages when 

 these insects were adapting themselves to their life con- 

 ditions, before man interfered with the natural order and 

 furnished various more or less artificial places for hiberna- 

 tion, these butterflies rested more generally upon the un- 

 der side of branches than they do now. 



Even in warm weather when one of these butterflies is 

 suddenly disturbed it is likely to fold its legs upon its body 

 and drop to the ground, allowing itself to be handled with- 

 out showing any signs of life. This habit is doubtless of 

 value, especially during hibernation or possibly during the 

 summer lethargy or aestivation, the latter a habit which 

 may be more general among these butterflies than is now 

 supposed. As the insect lies motionless upon the ground 

 it is very likely to blend so thoroughly with its surround- 

 ings that it becomes concealed, and any bird which had 

 startled it from the branch above would have difficulty in 

 finding it. 



Some very interesting observations have been made 

 upon the death-feigning instincts of various other insects, 

 especially the beetles. But no one so far as I know has yet 

 made an extended study of the subject in relation to our 

 American butterflies. It is an excellent field for investiga- 

 tion and oflFers unusual opportunities for photographic 

 records. One of the pictures opposite page 32 shows a 

 photograph which I took of a Mourning Cloak as it was 

 thus playing 'possum. This species exhibits the instinct 

 to a marked degree. 



