Page 22 - The Book of Caterpillars: A Life-Size Guide to Six Hundred Species From Around the World

THE MIRACLE OF METAMORPHOSIS

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above left to right leaving the pupal case that has formed beneath. In most species, final
The final caterpillar
molt into a pupa or coloration of the pupa matches its immediate environment. Even the
chrysalis is complete
in just a few minutes. Monarch butterfly (Danaus plexippus), which is brightly colored at all
Here, the larval skin
of the Two-tailed larval stages to alert predators to the toxins it contains, does not advertise
Swallowtail (Papilio
multicaudata) is intact this fact at pupation; its green pupa blends with the foliage around it. While
in the left image,
but in the center pupae may occasionally wriggle if disturbed, they are generally
image it has peeled
back to the lower unobtrusive, remaining hidden or camouflaged to avoid predation at
part of the body.
In the right image, this crucial stage.
the skin has dropped
away leaving the new Larvae that form hanging pupae adopt a characteristic J shape. After
soft pupa to harden.
12 to 48 hours, the larval skin splits behind the head, revealing not another
caterpillar integument, or skin, but a fleshy, soft integument, usually green,

yellow, or orange. With much wriggling, the larval skin moves down the
body, revealing increasingly more of the soft, new pupa. Once the shed
skin reaches the terminal segment, the pupal cremaster probes and seeks
the silk pad spun earlier by the prepupal larva. With hanging pupae this is
a critical phase; if the cremaster fails to make contact with the silk pad to

which it attaches with tiny hooks, the soft pupa will fall, and likely perish.
After attachment, more wriggling usually results in the shed skin dropping
away, and eventually the pupa stops moving, hardens, and assumes the
coloration that allows it to blend in with its environment.

THE TRANSFORMATION
Within the pupa a remarkable process takes place. Hormones trigger the
release of enzymes that break down the larval structure into a sort of
“soup,” containing tiny, disc-shaped groups of cells, present but suppressed