Posted: July 17th 2019
by Andy Bloomfield, NNR Warden
One of the most intriguing events each summer is the arrival of various insects from the Continent. We all have it in our head that birds commonly migrate across oceans, but many people just do not associate insects as being creatures that travel great distances and across the sea. Nothing could be further from the truth; there are some species that habitually arrive here in the UK from overseas whilst others appear from time to time as a reaction to either hot winds blowing from Europe and sometimes even north Africa or a rapid and sudden population explosion. Such movements are often linked to climate change which then leads to more permanent colonization into new areas.
One species that started to arrive in early June and accelerated as the month progressed was the Painted Lady Butterfly. Although they arrive annually from the Continent and breed here, periodically larger ‘invasions’ also occur. Painted Ladies are really interesting in the fact that they regularly undertake a huge migration from within the desert and mountains of North Africa. Given the right conditions, often just a spell of localised rainfall in the desert, it can prompt rapid vegetation growth and maybe the right food plant (which is thistle here in the UK) and then breeding occurs. From here the butterflies start to migrate north through coastal Morocco and Spain before hitting the UK. In some years such as 2009 when some 11 million were estimated to have arrived in the UK, the butterflies have continued north, with some even reaching Iceland. This year’s numbers have not reached those heady heights but there has certainly been more than average to make 2019 a memorable year. One of the biggest concentrations this year was in the Walled Garden on the Estate. Here some 60 were seen festooning one bush. A real blizzard of colour.
Other than butterflies, this year has seen a remarkable influx of unusual dragonflies. These too have arrived from southern Europe and have included species such as Red-veined Darters, Lesser Emperors and the exceptionally rare Vagrant Emperors. Red-veined Darters appear every few years (although more frequently recently) and are a beautiful and startlingly vibrant red colour. The red extends up the veins within their wings (hence their name) and they have striking two toned red and blue eyes. Of the trio of migrants, the Vagrant Emperor is certainly the most unusual. It had been recorded at Holkham only once before and in fact very few times in the UK.