For the first time in more than a century, the microscopic eggs of an elusive butterfly have been found in Scotland. After having suffered a dramatic decline in the 1970s, it signals the butterflies are returning to the area.
It comes after an adult white-letter hairstreak was spotted last August 10 miles away – the first sighting since 1884.
“Last year was an impossible find, but this year’s egg discovery is beyond anything we thought possible,” Iain Cowe, a butterfly recorder who spotted the adult butterfly last summer, told the Guardian.
Volunteers from the Butterfly Conservation found the eggs, and among them an old already-hatched shell. Since the butterflies breed annually and often use the same location, specialists say that means it might have been breeding in Scotland since at least 2016
The White-letter Hairstreak only lays eggs on wych elm trees and suffered a 72 percent decline because of Britain’s ongoing battle with Dutch Elm Disease. It’s one of the most serious tree-killing diseases in the world and has killed over 60 million British elms in two epidemics.
Crowe’s spotting of the flying insect last summer was only the third time ever being recorded in Scotland. The last time was in 1884 and before that 1859.
Named for the distinctive “W” marking on the underside of its week, the white-letter hairstreak only eats elm trees. While scientists remain concerned about the UK’s dying elms, butterfly conservationists are equally concerned about the extinction of their biggest fan in the British Isles.
Despite a particularly horrendous butterfly year in 2016, populations have slowly spread in recent years.
Colonies are very small and often only contain a few dozen eggs, which are always found on elm trees. Adults emerge toward the end of June and reach sizes of 25-35mm. Most butterflies hibernate as caterpillars, but the white-letter hairstreak spends nine months as an egg, smaller than a grain of salt and stuck to slender branches of elm.
They nest in heavily-wooded areas, or even on clumps of trees in urban centers. Some 200 miles away, for example, there is a butterfly colony has taken up residence in the middle of a town and sparked up quite a bit of controversy.
Found throughout Europe, the white-letter hairstreak is not a species of concern across the continent. Its return, however, bodes well for both butterflies and elm trees.