Nature Notes: All Change
One of nature's most remarkable miracles is the creation of a butterfly, from egg to caterpillar through chrysalis stage to perfect insect.
A caterpillar feeds voraciously, grows rapidly, changing its skin several times. When fully grown, the great transformation begins. The comma butterfly caterpillar finds a plant stem, spins a silk pad, attaches the end of its abdomen to it and hangs down in the form of a letter J.
After a few days it wriggles violently, sheds its skin for the last time to reveal a soft chrysalis which soon hardens. At this time great chemical and physical changes occur. The caterpillar's cells dissolve into a green soup within which cells regroup inside the chrysalis to form the butterfly.
The chrysalis stage lasts about two weeks, then early one morning the skin splits and, probably more easily than we struggle to open a packet of biscuits, the butterfly slowly and carefully breaks free, ensuring that it is hanging upside down in a clear space to enable the wings to inflate. If the developing wings touch a leaf or obstruction they become deformed and the insect cannot fly.
The photo shows a late season comma butterfly hanging upside down by its vacated chrysalis. Then, at midday, I watched it vibrating its wings to warm flight muscles and minutes later zoom up on its maiden flight. It will build up fat reserves with nectar from autumn flowers before hibernating on a tree trunk or in leaf litter, where its ragged wing outline, resembling withered leaves keep it superbly camouflaged.