The end of the beginning

Otherwise known as January’s month-end abstract:

tight crop of hindwing of Low's swallowtail Papilio lowi
I said this might be back, and you scoffed – don’t deny it, I heard you distinctly all the way over here. So let’s gaze deep into the hindwings of the Low’s swallowtail (Papilio lowi) and the curious pattern thereon. Don’t ask me what exactly it accomplishes, but I want you to see something. From a short distance, the wings appear to have gradient tones, shading that almost gives them a three-dimensional shape, but on close examination we can see that the scales come in only two colors, black and pale blue. The shades are produced only by distribution, a lower density of the blue scales giving more of an impression of shadows. This is almost a good mimicry of hollow tubes or stems, but there’s a flaw: the centerline of each should be the brightest blue to carry the impression, the reflection of more direct sunlight, rather than having a darker line which hints at a hollow or crease. Again, I can’t think what this is supposed to communicate, if anything – it might simply be to attract the attention of predators more towards the non-vulnerable hindwings, or it might be a sexual display, or simply something to confound bloggers…

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