Checked 9 wild iris larvae in stultifying heat (optional clothing weather). One had recently changed into the final instar and 2 more larvae were skin changing into the final (5th) instar. The rest were all in the mid 4th state apart from one laggard who is in the early 4th state.
6 had moved distances of between .4m to 2.2m, and I couldn't find one who must have gone >3m (will check again). They are feeding strongly in this fine weather.
What does this mean? We're probably on for a late June emergence but much depends on how long it takes them to pupate, which is weather influenced, and June weather generally.
Some of my captive larvae are more advanced, mid way through the final instar, but I will be putting most of these out in the wild soon, to stand a chance of finding pupae.
Watch this space, we should be able to predict the start of the 2010 flight season quite accurately...