Peacock Butterflies Aglais io normally produce just a single generation of adults each year in the UK although occasionally a second generation may be seen if conditions are suitable. The adults emerge in the summer and then enter into a state of inactivity as early as August (?aestivation leading to hibernation) to emerge again during the following spring when the weather is warm enough and there will be plenty of Stinging Nettles Urtica dioica on which to lay their eggs. Individual butterflies will therefore need to have survived for quite a number of months before they are able to reproduce. In order to achieve this Peacocks are aided by some useful defensive devices. Firstly the underside of the wings is extremely dark and exquisitely patterned to resemble the bark of a tree. If at rest with the wings closed this makes the butterflies difficult for predators (mainly birds) to see. If a butterfly is disturbed it can then use an element of surprise by suddenly revealing striking eye-spots on each wing. If this shock tactic fails Peacocks are also able to rustle their wings (although it is probably debatable if this provides much of a deterrent). Spring adults are usually somewhat the worse for wear after having been exposed to the many hazards that they might meet and the wings are often damaged and torn with scales missing. This nine month old individual appears to have fairly limited damage to the rear of its hind-wings as most of the scales are intact.
