How do adult butterflies and moths emerge from their pupal cases?

Adult butterflies and moths emerge from their pupal cases—a process known as eclosion—through several specialized methods depending on the species.12

To escape a cocoon, some moths utilize mechanical tools, such as movable mandibles in primitive species, saw-toothed structures on the head, or bladelike appendages on the wing bases. In other instances, such as with puss moths, the insect secretes alkaline fluids that dissolve the silk of the cocoon. Generally, the adult may also emerge by splitting the pupal skin or chewing its way out.31

Once free, the adult crawls to a position where it can hang with its head upward and back downward. It then expands its wings by contracting its abdomen to pump body fluids into the wing pads. After the wings reach their full size and shape, the insect must wait for them to stiffen before it is capable of flight, a process that can take anywhere from a few minutes to several hours.3