Berkeley's Swallowtails...what is that thing?!

What is that weird thing?!

I remember the first time I saw a swallowtail pupa...it was startling, and strangely disturbing. There is an alien quality about the shape, and perhaps resonance with memories of pictures of mummies or quadruple amputeeism. Also perhaps a hint of claustrophobia--it's easy to imagine being locked inside, utterly helpless and vulnerable.

The conversion of a J-shaped suspended caterpillar to a pupa is pretty fast, lasting only a few minutes. It starts when the caterpillar begins to wriggle and writhe, doing just the sort of movement you'd expect would be needed in order to wriggle out of a whole-body leotard without any helping hands. The initial split in the skin occurs at the top, and reveals the green-white pupa within:

More writhing, and the split spreads downward. The skin is so thin that its edge is virtually invisible...you only know it's there because of the colors.

More writhing. This is an unusual pupa, with what looks like a "face" composed of darker pigment.

The skin looks somewhat baggy as it pulls away from the pupa. In the photo below, you can barely make out the silken "harness" loop crossing the triangle-shaped black section of skin on the left. The skin is not attached to the harness loop, and as the split reaches the loop, the skin slips easily out from underneath the loop. This seems a little surprising, since silk tends to be pretty sticky stuff when first made. I wonder what keeps it from sticking to the skin.