Once a caterpillar becomes a chrysalis, it may remain in that state for 10 days to 2 years. The time varies by species and the season in which the chrysalis is formed. Those that are formed in the fall usually do not become mature butterflies until spring.
Butterflies go through four life stages: egg, caterpillar, chrysalis and adult. During the chrysalis stage, the tissues of the caterpillar are broken down and reassembled into the tissues of the adult form by specialized groups of cells called imaginal discs. Each disc is formed within a caterpillar while still in the egg and carries the programming for a specific adult body part.