“Now if, as Weismann has attempted to show for larvæ and imagines, the form-divergence always ‘corresponds exactly with the divergence in the mode of life,’ the question arises as to what difference in the conditions of life has brought about such a considerable form-divergence between the pupæ of such closely allied species as the Maracujá butterflies. In pupæ which do not eat or drink, and which have neither to seek in courtship nor to care for progeny, it is only protection from foes that can concern us. But in the pupæ of nearly allied species of which the larvæ feed on kindred plants in the same districts at the same periods of the year, can the enemies be so different as to produce such a considerable divergence in form? One might answer this question in the negative with some confidence, and affirm that in this case the difference in the pupæ does not result from the ‘divergence in the mode of life,’ or from the difference in the external conditions, but is accidental, _i.e._ a consequence of some fortunate variation induced by some external cause, which variation afforded protection against common foes--to one species in one way, and to the other species in some other way; this course, once entered upon, having been urged on by natural selection, until at length the wide divergence now shown is attained. How in the case of any of the species the peculiarity in colour or form can actually serve as a protection, I must confess myself at fault in answering. Only in the case of the pupa of _Eueides Isabella_ will I venture to offer a supposition. That it is not green like other pupæ which suspend themselves among foliage (_Siderone_, _Epicalia,_ _Callidryas_, &c.), but contrasts more or less brightly with the dark green of the leaves, precludes the idea of concealment; on the other hand its colour is too dull to serve as a conspicuous sign of distastefulness. In either case the meaning of the wonderful processes of the pupa would remain unexplained. “We are thus compelled to seek another possibility in mimicry, by which foes would be deceived by deceptive resemblance. But what is the object imitated? Dead insects overgrown by fungi are often found on leaves, the whitish or yellowish fungi growing from their bodies in various fantastic forms. Such insects of course no longer serve as tempting morsels. The processes of the pupa of _Eueides_ suggest such fungoid growths, although I certainly cannot assert that to our eyes in broad daylight the resemblance is very striking. But the pupæ hang among the shadows of the leaves, and a less perfect imitation may deceive foes that are not so sharp-sighted; protective resemblance must commence moreover with an imperfect degree of imitation.” EXPLANATION OF THE PLATES. PLATE III. Figs. 1-12 represent larvæ of _Macroglossa Stellatarum_, all bred from one batch of eggs. Most of the figures are enlarged, but sometimes to a very small extent only; the lines show the natural length.