Transformer

When our kids were small they collected toys called transformers, which were model vehicles that turned into menacing robots when you pulled, twisted and rotated their articulated parts. They were marvels of imaginative, miniature engineering but couldn't hold a candle to this wonderful natural transformer - a cabbage white pupa, which I found under the rim of a seed tray in the greenhouse yesterday. Insect metamorphosis is one of the most mind-boggling developmental transformations in the natural world.

Inside this pupal case the caterpillar - an insect eating machine that chewed holes in our broccoli leaves is turning into a 'soup' and reorganising itself into a delicate, winged, nectar-feeding cabbage white butterfly that will emerge next spring.

The caterpillar has pupated fairly recently - over the winter its green shade will turn to pale brown. If you look closely, about one third of the way down the image you can see the silken halter that the caterpillar spun to attach itself to the seed tray - it's last act as a caterpillar.

Click here to see a great YouTube movie of a large white butterfly hatching from its pupal case.

You can read about the biology of insect metamorphosis by clicking here