Metamorphosis: larval stage
|The larval stage is actually the growth stage of the
metamorphosis. Often the first meal of a caterpillar is the eggshell. The eggshell is not
made of chitin but of a rich fat-protein compound. Even though caterpillars may look quite
different they share one important feature: the possibility to molt. Both the head of a
caterpillar and is skin are made of indigestible chitin.
|A caterpillar's skin is elastic and contains stretch receptors. If the skin is maximally stretched these receptors submit a signal to the brains. The brains ensure that the molting hormone ecdyson and, when the caterpillar is not fully grown yet, the juvenile hormone are submitted into the bloodstream. If these hormones both are available the new skin will be a caterpillar skin, if just ecdyson is available in the bloodstream the new skin will be a pupal skin. Signals from both the extern and the intern environment are responsible for the presence of the hormones.|