quent sunbeams which is the headquarters of sara, and other yellow and black 

 or green and black 'aerial' butterflies. In their perching, too, they show 

 infixitude of habits, often sitting with wings closely folded and sometimes 

 with wings more or less expanded. Their upper and lower sides are much 

 alike, but the lower has usually a somewhat finer pattern, which is highly 

 'obliterative,' although less definitely and minutely 'ground-picturing' than 

 most of the patterns worn by true terrestrial 'sedentaries.' In fact, the 

 costumes of these more sluggish "heliconoid" butterflies contain just such 

 a compromise between bolder obliterative flight-patterns, in foliage and sun 

 and shadow tints, and finer, brown-ground-picturing perch-patterns, as a 

 knowledge of their habits would lead us to expect. The supposed mimetic 

 interresemblance of these butterflies' costumes was alluded to, though not 

 specifically, in our Introduction. Another group of South American butter- 

 flies, believed to show the same sort of mimicry is made up of species with 

 more or less transparent wings. These also are aerial, their wings are long, 

 and marked, in various patterns, with opaque bands and spots of dusky, or 

 sometimes brighter color, inclosing spaces of pure glassy transparency. Of 

 course these insects are normally almost invisible, not only when they sit still 

 (with a background of green leaves or brown ground, or what-not) but even 

 in their leisurely flight through the forest aisles. "One of these clear-wings," 

 says Bates, the great English naturalist, in his wonderful book "A Naturalist 

 on the Amazons," "is especially beautiful, namely the Hetcera esmeralda; it 

 has one spot only of opaque coloring on its wings, which is of a violet and 

 rose hue; this is the only part visible when the insect is flying low over dead 

 leaves, in the gloomy shades where alone it is found, and it then looks like 

 a wandering petal of a flower." 



Iridescence plays a great part in the 'obliteration' of butterflies, especially 

 aerial ones. Indeed, splendid iridescent colors are enrolled in the service 

 of the more restless butterflies with an amplitude and variety scarcely to be 

 matched in the world of birds. We have already (Chapter XVI) given a 

 general analysis of the obliterative power of highly changeable color. The 



224 



