Pupal Stage

Image: Hanging larva Image: Pupating larva

Above you see caterpillars that are about to pupate (i.e., to become chrysalises), and one that has just done so. After hanging upside-down for about 12 to 15 hours, the caterpillar removes its skin to reveal a squirming green pupa. For several more hours the pupa's skin smooths over to become the mature chrysalis.

Most butterfly chrysalises aren't beautiful at all; they're drab brown or gray, with bumpy exteriors. The Monarch's chrysalis is unusual in being a beautiful, smooth object, green with golden spots. If you look carefully, you can see parts of the future butterfly. Just as the caterpillar hung with its head down, so is the butterfly positioned head-down in the chrysalis. In the first picture below, the left-hand chrysalis has the butterfly's back (dorsal side) facing you, whereas the chrysalis on the right has the butterfly's ventral side facing you, with legs and antennae extending upward between the wings. The two protruding gold spots at the bottom of the chrysalis are positioned over the butterfly's eyes.

Image: Back and front views of Monarch chrysalis Image: Side view of Monarch chrysalis

The chrysalises shown below were made while the leaves were still on the milkweed plants. Later, after they had smoothed over and hardened, we clipped the leaves and taped them to an old lamp shade, creating a kind of living ball fringe!

Image: Chrysalises on lamp shade

The pupation process is fascinating to watch. Initially, the larva is suspended by its rear legs, whose tiny claws are embedded in a silk button that the larva has spun on its chosen support. These legs are part of the skin, which the pupa must now remove. The larval skin is delicately attached to the pupal skin in the area between the last two pairs of legs. As the hanging caterpillar wriggles, the larval skin splits behind the head and is gradually pushed upward toward the point of suspension. When the skin is all bunched up at the top, the pupa flexes to one side, withdrawing a spiny black stem from under the skin. Without the benefit of eyesight, the pupa skillfully thrusts the stem into the silk button, entangling its many tiny spines in the silk. It then gyrates wildly, breaking the bond between the larval and pupal skins that had supported it before, and drops the larval skin to the ground. It flexes a few more times to ensure that the skin is gone, then settles down to become a smooth chrysalis.

Download and watch some amazing videos of the larva pupating and the new pupa contracting. These videos are about 15 MB and 7 MB, respectively. If you're on a dial-up connection, you may wait a long time for them to download. These videos are Copyright (C)2003 by Clay Ruth. You have my permission to use them in an educational or home environment at no charge. Distribution for profit is expressly forbidden. If you do not agree to these terms, don't download the videos.

The chrysalis remains stationary for nine to ten days. Then it darkens, and the butterfly emerges.

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