Peacock Butterfly (Inachis io) This is the most colourful butterfly normally seen around the College and it is usually on the wing from June to September. The two large iridescent blue eyes on each of the dark red wings make it very easy to identify. The purpose of these is to startle intending predators when the wings are opened suddenly. The black underwings make it surprisingly difficult to see when at rest. The caterpillar is black with spiny protuberances along its back and orange/brown prolegs: It feeds on nettles which are very common in the Deerpark.