Stripping Off the Striped Body Suit

The pupa is the emergent phase from the familiar caterpillar. In a matter of minutes after relaxing limply from the 'J' shape, shedding of the skin begins with a split behind the head. With convulsive waves the skin is forced back over the pupa toward the area of attachment. The disrobing pupa accomplishes this feat by expanding itself to burst off the old skin. Much like a toddler would do, it allows the outfit to "fall" at its feet. But, the pupa hangs upside down by its feet the whole time! The shedding skin is forced up and off. The skin becomes a crumpled pile, to be got rid of.

Now, in a daringly acrobatic and delicate move, the pupa transfers grasp of the silk web 'button' from the anal prolegs of its larval stage to the cremaster of this newly developed pupa. The act means slipping the cremaster out of the prolegs like you would take your hand out of a glove: while holding on to a limb! This pupal cremaster consists of a number of hooks that enmesh in the 'button' of web silk much like a Velcro® fastener. If this is a miss-step, the pupa can detach and fall to a certain death.

There are two fasteners that keep the skin secured to the caterpillar during this risky maneuver, called holdfast tubercules. They'll "unsnap" when the caterpillar's grasp is successfully transferred. The caterpillar wriggles vigorously to loosen their grip on the skin.

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