There are two generations in a year. I have not been able to work out precise boundaries, and I believe there is partial overlap between the generations. I have seen adults from June to September, full grown caterpillars from April to September, and young caterpillars in January. Eggs are laid in neat and regular arrays on the underside of a leaf of willow, snowberry, dogwood and doubtless many other shrubs. Many geometrid caterpillars stand out at an angle from a twig, as in the photographs of Pero mizon. C. perlata adopts a different strategy. It appresses itself closely against a twig, and it has a fringe of short, fleshy bristles along its side, which hug the twig, making the caterpillar difficult to see. The caterpillars of the lasiocampid genus Epicnaptera and the noctuid genus Catocala do the same thing very successfully. The caterpillar of C. perlata has a small extra pair of abdominal prolegs compared with the majority of geometrids.