Remember the peacock caterpillars that Ian found in the nettle beds between Simpson’s Field and the Arboretum?
At the weekend, he found and photographed one of their chrysalises hanging from a nettle stem. He emailed this:
‘When walking back from the work party last Wednesday we had a look at the nettle patch in Simpsons where there had been several Peacock nests. Today I had another look and found a chrysalis – rather beautiful.’
Inside a chrysalis, the caterpillar produces enzymes and, in effect, digests itself. If you were to cut open a chrysalis at this stage, a kind of caterpillar soup would ooze out. In the soup are imaginal discs: small, highly organised groups of cells that survive the digestive process and act like a blueprint, an instruction manual, for building a butterfly.
When a caterpillar is developing inside its egg, it grows an imaginal disc for each of the body parts it will need as a mature butterfly: leg imaginal discs, antenna imaginal discs, wing imaginal discs and so on. Inside the chrysalis, triggered by the enzymes, the imaginal discs, just a few cells at first, begin to grow rapidly. They use the proteins from the caterpillar soup as fuel, and grow all the bits needed to make an adult butterfly.
It takes about two weeks to assemble a butterfly this way but not all species hatch immediately; some can delay hatching, sometimes for years, until the conditions are right. The peacock butterfly does seem to delay its hatching until the early morning of a fine day about two weeks after pupation.
So, early morning dog walkers, please keep an eye out in the next few days for an adult peacock butterfly somewhere near the nettle beds on the right hand side of the track as you go up the hill.
Click for more butterflies: