As the numbers of painted lady butterflies continue to amaze, a report from 1877 about clouded yellows may be of interest. Henry Ullyett gave a talk to the Folkestone Natural History Society, printed in his book Rambles of a Naturalist round Folkestone etc.
1877 was "the great Edusa year" when "hundreds of Clouded Yellow Butterflies covered the slopes of our Folkestone hills", and "hunters with the net" made the most of the opportunity.
The first appearance was on 6th June, when he pondered when they might be "hybernated" although some seemed fresh from the chrysalis. Then on 3rd August, the large numbers started to appear "and from this time onward for nearly four months the whole neighbourhood abounded with them, the fading specimens of the second brood mingling with the fresh bright ones of a third in October". Specimens were taken until the 12th November even though the year was "one of the wettest and most sunless years remembered for some time".
The butterflies are "very capricious in their times of appearance" and "every now and then there is a great swarm of them". There was an old tradition that there was an Edusa year every seven years "but this has been broken down by stubborn facts". More recently, good years have included 1947, 1955, 1983, 1992, 1994, 1996 and 2000. Ignoring an inconvenient years of 1994 and 1996, the intervals since 1947 were 8, 8, 9 and 8 years, so 2009 should be another good one.
He recalls 1872 as a "Camberwell Beauty year" when there were also many Bath whites and Queen of Spain butterflies.
The clouded yellow is a fast flyer, which gave Ullyett some trouble in catching them. He gives advice : "do not wait till midday when the hot sun inspires the insect with unusual vigour ....I can assure you that it is no joke racing over the Folkestone downs after it then.
"The wise plan is to go out early in the morning when the sun has just, only just, driven off the dew. Edusa is rousing itself, and rising lazily only to drop again a short distance ahead. Mark the spot, walk up quietly and put your net over it."