What to look for this week - Beautiful Butterflies
Published: 09 June 2020
Here come the butterflies
What a glorious few days of sunshine we’ve just experienced and as might be expected on such fine weather days with warm winds from the south butterflies started to make an appearance. Our resident Large Whites (or cabbage whites) are around, there were a handful of reports of migrant Red Admirals and a much scarcer Small Tortoiseshell was seen.
There are only four butterfly species regularly recorded in the islands. Three of these are migrants – Red Admiral, Painted Lady (pictured here) and Small Tortoiseshell while the Large White is resident in the island – its caterpillars feed on brassicas which make it perhaps the UK’s least-loved butterfly; it too can arrive as a migrant in good years.
Red Admirals (pictured top) and Painted Ladies (pictured right) arrive in variable numbers; last year was a bumper one for Painted Lady with two huge influxes, possibly the largest in living memory. Hundreds were recorded in early June and again at the end of July/early August. Painted Ladies do not hibernate at any stage of their life cycle and their caterpillars cannot survive in temperatures of lower than 5 degrees centigrade so they aren’t resident in most of Europe, yet thousands occur every year with a few making it to Shetland and odd ones even as far north as the Arctic Circle! These, or perhaps their parents or even grandparents, originate from breeding grounds in North Africa where vast numbers emerge in early spring every year. They head north on a broad front across the Mediterranean navigating with a solar compass and invade Europe. The life cycle from an egg through a caterpillar and chrysalis to an emerging adult can take as little as six weeks and the butterflies mate and lay eggs as they head north. So, in a fine summer several generations are born and continue the relentless movement north; you can often tell a new generation individual from an older one by looking how fresh the wings are. Migrants can often be seen flying north in a straight line just 1-2 m above the ground but similar south-bound movements were never noted and this led observers to believe that the butterflies eventually just died in Europe. Recent studies using vertical radar however, discovered that there was in fact a massive migration of Painted Ladies back south but this was happening out-of-sight several hundred metres above the ground. The butterflies choose days with strong following winds and off they go. Indeed, it appears that more butterflies arrive back in North Africa in the autumn than left in the spring – although of course these are the offspring.
One butterfly that was once a rarity here but is now seen every summer and in increasing numbers, is the Peacock and it is tempting to think that this is a product of global warming. This butterfly with its dramatic ‘eyes’ on each wing is incredibly striking – these ‘eyes’ have evolved as a defence tactic. The butterfly sits with its wings closed when it is surprisingly well camouflaged but if it is surprised by a potential predator a quick flash of those ‘eyes’ causes enough of a shock to the predator to give the Peacock time to escape.
Insects are one of the groups that react quickest to global warming so we ought to keep our eye out for more potential additions to Shetland’s butterfly list. Both the Small White and Green-veined White breed in Orkney and may have occurred here naturally but a photograph would seal the deal and enable the observer to take their place in Shetland butterfly history! And perhaps a Comma might make it here – they have been moving north into Scotland at a rapid rate. If we are very fortunate then the Common Blue could recolonize Shetland – it survived here for a few years in the 1960s and 1970s but has since disappeared. Sometimes really spectacular butterflies find their way to Shetland – in the last couple of years Clouded Yellow, Camberwell Beauty and a Monarch all the way from the USA have been found in Shetland!
All records of butterflies would be welcome at the Shetland Biological Records Centre and we are happy to try and identify any photographs if that helps – send them to Paul.firstname.lastname@example.org A leaflet to help you identify butterflies can be found on the website
Paul Harvey, Natural Heritage Officer, Shetland Amenity Trust - June 2020
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