3rd molt completed: 4th instar caterpillar of the Cecropia moth

Overnight this caterpillar molted for the third time and is now a 4th instar larva of the Cecropia moth.

The most noticeable changes in appearance are the loss of any spots on the skin, and the variation in the color of the spicules (the spiky projections along the body). Up til now all of the caterpillar’s spicules have been a uniform shiny black. Now the two rows along the dorsal surface are yellow while the lateral spicules remain black.

The caterpillar’s skin is a beautiful shade of pastel green and blue.

Getting ready to molt: Cecropia moth caterpillar

Cecropia moth larvae (caterpillars) go through four molts as they grow. The stages between molts are called “installs”. So-called “first instar larvae” are caterpillars that have hatched from their eggs but not molted, and the caterpillars that have molted four times are called “fifth instar”. By the time they reach the fifth instar stage, they can be the size of an adult finger, and at that stage they spin a cocoon inside which they will molt again into a pupa that overwinters before emerging as an adult.

This caterpillar has molted twice, and is therefore a “third instar” caterpillar. It is about an inch long at rest:

This one is getting ready to molt. The evidence includes:

  • taut skin - the caterpillar looks like a spiky sausage,

  • lack of movement for 24 hours or more, except for an occasional twitch or body twist,

  • some cloudiness around the head capsule.

The caterpillar typically rests with its head curled under its body as seen here. As it gets closer to molting, it will start to stretch and wavelike motions will originate from the tail which the caterpillar anchors down with a bit of silk. The skin will split open just behind the head and will slide back towards the tail as the caterpillar’s body expands forward and it stretches out of the old skin.

No chest of gems could match it.

The amazing textures and colors strewn over the landscape of Petrified Forest National Park near Holbrook, Arizona.  Gun metal alabaster chalk dust on corduroy mahogany bubbles.  Sawdust in snow on scorched jerky leather lightning pearlescent mustard chrome.  Diamond charcoal velvet frayed cowhide smoke frozen seawater glass.

Click any image for larger.