198 ANIMAL COLOEATION. 



clumsy flight of the uisect, which causes it to come against 

 obstacles instead of neatly avoiding them, as other butterflies 

 do who thread their flight among the most confused network 

 of branches of a tropical forest. It is a more obvious sugges- 

 tion that the wings of this insect have been rubbed through 

 contact with birds' beaks — their elastic structure saving them 

 from breaking. 



Dr. Seitz, however, particularly says that birds do not 

 attack this Ao^cea ; he never saw a bird attack one of these 

 insects, nor observed their wings lying about on the ground, 

 as one sometimes (rarely, however, be it remarked) sees the 

 wings of lepidoptera in this country. 



Another suggestion may be made to account for this rubbing 

 of the wings ; and that is that they have been produced by 

 ineffectual attempts on the part of bats and nocturnal birds 

 to seize the insect. Now, butterflies are for the most part 

 diurnal in their habits, as the name " Diurni," sometimes 

 applied to the group, attests ; but they are not exclusively 

 so. I have myself seen butterflies on trees " sugared " for 

 the purpose of attracting moths, and I believe that this 

 experience is not uncommon. These instances are probably 

 due to exceptional circumstances, such as the proximity of the 

 resting-place of the insect to the sugared tree. But in Central 

 America Heliconids have been found lured into the towns by 

 the electric light ; and there seems to be some evidence for 

 the partially nocturnal habits of certain Heliconids. 



If these Acrasas are not nocturnal, it is jjossible that thej' 

 pass the night on a leaf or tree trunk, and might often be 

 snapped at by a passing bat or goat-sucker. The particular 

 species of Acrcea which is referred to is normally covered with 

 scales, but there are other species whose wings are normally 

 nearly transparent. 



