Observations of the Spotted Tussock Moth Larval Stage: page 2
After the moth laid eggs on the side of the cage, Zoe and I got excited and decided to start making formal observations on how the larva develop. The eggs hatched after eight days and we had tiny gray, fuzzy caterpillars about 1 mm long. We observed them through a microscope. We knew the caterpillars would need to begin eating at once, so we placed them on leaves of the big leaf maple, a tree common in coastal Oregon. It turned out they really liked the maple leaves and ate vigorously. Zoe continued to transfer them to fresh leaves. They grew rapidly and began to molt.
The caterpillars went through 4 molts. The stage between each molt is called an instar. Our caterpillars had five instar stages, in each of which the caterpillars had a different pattern of coloration. In each stage the caterpillars grew larger until by the end of the summer they were about 1.5 inches long. The first three instars are shown below.