The caterpillars are green with a darker green line along the back, bordered by two light stripes. Their sides are marked with white parallel lines, and sometimes a row of black spots.
Caterpillars reared from the same batch of eggs differ in their degree of spotting. Each spot is actually at the base of a hair. These hairs are found on the thorax and on the first seven abdominal segments, just above and in front of a spiracle, or on a level with hairs on segments with spiracles. The spots may be in various forms: solid black extending to the base of the hair, or a black circle around a green base to the hair, or a solid black semicircle, or absent altogether. In the latter two cases, the hairs are smaller!