Williamson's Weekly Notes August 19 2009

A friend said that while standing on Portsdown Hill the haze southwards resembled diesel smoke from liners and ferries. Another saw the same phenomenon on Dover cliffs. Pundits reckoned five million flew in from the south, a vast irruption emanating in the Atlas mountains.

I noticed while on farmland fields near Petworth that many butterflies had lost the colours on their wings and were flying without identification marks. I could almost see through their wings, although I suppose they resembled pieces of varnish paper giving them a most unusual appearance.

All of these insects were behaving like lemmings of course, quite unable to avoid the directive in their stupefied brains implanted by a dictating hormone, to avoid overcrowding at all costs and give their young ones a chance in foreign lands out of Africa. Some actually tried Iceland as a possible new colonial territory.

Others went to Murmansk and found the place a little hostile too. Lots stayed in dear old Blighty, which welcomes everyone from abroad. Here they quickly set up home on their favourite habitat '“ the thistle. Others laid eggs on viper's bugloss, mallow and burdock.

They do not seem to have colonies like others in the Vannesinae such as the red admiral where colonies of furry black caterpillars are found on nettles. The painted lady lays her eggs singly on individual leaves, even many different plants, so the developing caterpillars are not easy to find.

Nevertheless, they are big, blackish, and hairy. Sometimes they have been known to eat the leaves of runner beans. Well, two months almost to the day after arrival of the parents, the children were on the wing, estimated to be a billion of them.

In 40 years or more of butterfly watching I have never seen a sight like that of July 25 this year that greeted my eyes upon the downs.

Hundreds, if not thousands of fresh young painted ladies were swarming just as their parents had done in Morroco in the spring.

They were covering the marjoram flowers with their lovely salmon-pink wings. The swarms were bigger than those of 1996 and 1980 by far. My sampling transects made every week, every year since 1976 prove that.

I cannot speak for the other great years of 1903 and 1889. I wish I could. As for the phenomenal immigration of 1272: that too is just a wee bit before my time as well.