among Sphinx larvae, which often have the leaf-vein markings exaggeratedly 

 developed. The Polyphemus caterpillar, which closely resembles the Luna, 

 largely lacks these markings, but has an even more leaf-like contour.* There 

 are few creatures in all nature better obliterated by shade-, color-, and pattern- 

 devices than are many of these large green caterpillars, which are doubtless 

 much sought after by certain birds, as for instance the Broad-winged Hawk 

 {Buteo platypterus). A human eye needs much training to be able often to 

 detect a Luna or Polyphemus caterpillar hanging amidst foliage. Fig. B shows 

 the same Luna caterpillar with the back uppermost, the reverse of the normal 

 position. It will be evident to any eyes that the creature thus placed, so that 

 the proper effect of its light-and-shade gradation is exactly and doubly thwarted, 

 is extremely conspicuous, and that neither its leaf-green color, nor its leaf-like 

 markings and contour, both so extremely useful when cooperating with the 

 proper effect of the fundamental light-and-shade-effacing. principle, can now 

 avail it. The creature is now staringly revealed as a fat green larva, light on 

 the back and dark with shadow below, — as even monochrome solid objects are 

 plainly revealed to the eye. Figs. C and D are two Sphinx-caterpiUar pic- 

 tures exactly corresponding to those of the Luna, as will be seen. Fig. C 

 shows the larva in situ, Fig. D reversed. An interesting modification of this 

 scheme is found in the caterpillar of Basilona imperialis, the Imperial Walnut 

 Moth. Lacking distinct leaf-markings, it is furnished with scattered, long, 

 light-colored hairs, which, when it is seen from a slight distance, completely 

 blur its surface, and greatly help its rough but adequately 'obliterated' green 

 body to blend with the general green of its foliage-background.f 



* The red warts, with a pearly luster, of which we have made no mention, and which are com- 

 mon to both species, are larger and brighter in the Polyphemus. Whatever may be their other uses 

 they lessen the larva's visibility, inasmuch as the tiny spots of gleaming light upon their tips suggest 

 to the eye the glinting of light through holes in the leaves. The huge and gorgeous warts of the 

 Cecropia caterpillar are not lustrous, and cannot serve this purpose, but they closely resemble dis- 

 ease-excrescences upon leaves, and may well be strictly disguising devices. Or they may be also 

 fixed defensive weapons, serving to make the larva unpalatable, as the branching bristles of the 

 Automeris io caterpillar certainly serve to make it dangerous, to a would-be devourer. 



t With us these caterpillars feed chiefly on red maple and white pine, and those of the bluish 



187 



