By the time you read this column, you may well have already seen the advance guard of a huge invasion. 2009 is set to be a Painted Lady summer. This attractive orange butterfly, its black forewings blotched with white, is a migrant from North Africa. Some arrive every year but the last time an influx on this scale occurred was in 1996. This year the first-comers were sighted on May 21st; numbers built up and headed north. The Butterfly Conservation web site contains reports of observers seeing thousands streaming overhead at Portland Bill in Dorset and fifty insects per minute flying in over the Norfolk coast. Having just returned from a holiday on the west coast of Scotland, I can confirm that small numbers had reached the shores of Loch Fyne by the 30th May, where we saw them flickering over the bluebells and rough pastures, no doubt keen to feed after their long journey.
And, what a journey! The first wave set out from North Africa as vegetation there dries up. They reach southern Europe and breed there. The next generation emerge and fly north to us. It seems incredible that such fragile creatures should be able to cross the sea, withstand the vagaries of the weather and elude all the predators which no doubt accompany such a mobile buffet, and still have the strength to mate and reproduce. What happens at the end of our summer is still a mystery. It seems likely that the summer brood return south. It has even been suggested that these insects make the entire journey back to Africa in one generation. Though obviously there are butterflies back there to start the next cycle, apparently there is no evidence to support this. I couldn’t quite imagine what such evidence might look like, so consulted our WNS expert. He explained that there is good evidence of a return to Europe of our other common migrant, the Red Admiral: sightings of clouds of departing butterflies near the south coast and further sightings in France. Nothing similar for the Painted Lady – so far.
And so – what about Wharfedale? Well, our expert has already had reports of sightings of seven to ten at a time. I’ve only seen one – in a friend’s Ben Rhydding garden. However, numbers will build up, and even more so when the second brood emerges. Before that, there will, of course, be painted lady caterpillars, Their preferred food plants are thistles and nettles on which the bristly caterpillars, black with a yellow trim, create their silken tents where they can feed safely.
Another cheering thought: late last summer, after a disastrous season for butterflies and moths, we suddenly had an influx of Small Tortoiseshell from the continent. Perhaps some of these will have survived the harsh winter to appear in our gardens over the summer. Let’s hope so.