Part 1 - The Peacock Eggs and Larvae
The Peacock is an iconic butterfly and its larvae are quite easy to find, but not many people have seen a Peacock pupa or can distinguish one from a Small Tortoiseshell (see: viewtopic.php?t=7156&start=10000
Eggs are laid in batches of 300-500 on the undersides of Common Nettle leaves, but unless you actually observe them being laid, they are quite difficult to find. The jade-green barrel-shaped eggs are laid in a compact mound, often piled 2 or 3 deep, which can take the female over an hour.
Upon hatching the young larvae spin a dense web of silk over the leaf and when this is consumed do the same thing at the growing tip of the plant, where they feed and rest communally. Safety in numbers is a defence strategy for this species, but living as a group also enables them to raise their body temperature above ambient levels, which means that they can remain active even in cooler conditions. They also need these higher temperatures in order to digest their food more efficiently.
Larval webs are easy to spot in June and early July and they seemed to be particularly abundant this year (2012) when I found 15 on sunny, sheltered nettle beds at a local site.
As the larvae grow and moult they move to different areas of the plant or fresh plants, leaving a trail of old webs, larval skins and droppings, making them even easier to locate. By the time they are in their 3rd instar they have acquired their full silky-black colouration with white spots, long dark spines and pale legs.
When ready to pupate a larva will usually leave the plant and spins a pad of silk on a stem or branch. Here it attaches itself, hanging head-down in the characteristic pre-pupation "J" shape for a day or two.
Just prior to pupation the larva straightens slightly and starts to pulsate its body. The skin also begins to look baggy, before suddenly splitting behind the head and gradually being sloughed off. This process appears particularly dramatic in this species because of the difference in colour between the old skin and the new pupa, which only serves to accentuate the variance in size between the two stages.
End of part one.