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  • Writer's pictureRoo

The beauty of the reclusive Hairstreaks!

There are five species of Hairstreak butterfly found in GB and none of them are easily seen without a bit of hard work. Four of the five species spend most of their time at the top of trees and the fifth sits hidden well-camouflaged on bushes and darts around in a flight so fast it’s hard to even see it’s a butterfly! However they are all beautiful and for me seeing any one of the five species is a highlight of my butterfly year.

A Green Hairstreak posing whilst taking nectar. The only species of Hairstreak that doesn’t involve getting neck-ache starring up at the tops of trees!

The Green Hairstreak is one of the commonest of the five, being found amongst low scrub on grassland and heathland habitat. Its caterpillars are quite easy going with regard to their foodplant, eating heather, gorse and bilberry for example. The adults are unique in GB being the only butterfly species with true green scales. They have a brilliant emerald green underside that is surprisingly good camouflage. The males have proffered perches on bushes and dart out in search of females. In flight the totally brown upperside is very hard to follow and they are easily lost to view. But with patience they often return to the same perch and can be quite approachable.

Lucky to find this mating pair of Green Hairstreak, note the bulge on the underside of the male (left-hand butterfly) forewing is the sex-gland producing pheromones to attract the female.

The Purple Hairstreak is probably the commonest Hairstreak and can be found in many town parks and even gardens where there are Oak trees. But this species, like the next three, is a species that sips honeydew from leaves on the tops of trees and rarely comes down to eye level. The adults are most often seen as silvery small specks flitting with a characteristic bouncy and buoyant flight of the hairstreak at or near the top of Oak trees. I’ve spent hours on a warm sunny evening starring through binoculars hoping for one to descend low enough to get a decent photograph! One good local site is Hendre Park in Cardiff, but they seldom seem to descend here and rarely come down to nectar on brambles and other flowers.

A Purple Hairstreak perched on an Oak leaf in Hendre Park, Cardiff

Possibly the most attractive Hairstreak is the Brown Hairstreak. The females, with luck, can be found egg-laying on hedgerows and bushes of Blackthorn or sometimes other Prunus species. They also take nectar from flowers more than other Hairstreaks. However when not doing so the males and females congregate on the tops of so-called “master trees” for mating. Look for them on tall Ash trees growing as standards in Blackthorn hedges.

A female Brown Hairstreak takes a rest between egg-laying.

Unlike Black, Green and White-letter Hairstreaks, Brown Hairstreak quite often show the upper wings. This is another female with bright orange patches.

A male Brown Hairstreak nectaring on bramble, and still quite high up!

The Black Hairstreak is the rarest of the five species and can be very hard to find. Some really good sites exist in Oxfordshire and Northamptonshire, with Glapthorn Cow Pastures, near Oundle being a famous site, along with Bernwood Meadow in Oxfordshire. The latter also has Brown Hairstreak and nearby are Purple Hairstreak. Most of the time, like Brown and Purple Hairstreak, the adult Black Hairstreaks spend most of their time sunbathing and sipping honeydew on tall trees such as Ash.

A newly emerged Black Hairstreak perched on the foodplant of its caterpillars, Blackthorn.

Possibly the hardest Hairstreak to see well is the White-letter Hairstreak. The caterpillar food plant is Elm and hence there was a marked decline in this species with Dutch Elm Disease. Where they still occur they can be quite common. In the Cardiff area there are some good colonies along the Taff Trail and I’ve even seen one on a small tree near St David’s Shopping centre in central Cardiff! This species, however, very much spends its time high up in Elm and Ash trees sipping honeydew and rarely flying. I’ve seen them in the tree-tops many times, using binoculars, but can count on one hand the number of times they have come down to eye level and only twice long enough to get a picture. In 1996 I was lucky to see them nectaring on bramble at Old Hall Marshes in Essex. Fifteen years later we saw one land on the grass in the car park at Castle Coch and a couple of years later I saw one perched on Bramble at a site in the Vale of Glamorgan. Only this year did I see this species nectaring on flowers again, 24 years after seeing this for the first time. Not the most spectacularly marked of GB butterflies, in fact a little darker than Black Hairstreak and without the shining colours of Green, Brown and Purple Hairstreaks, but the excitement of seeing a White-letter Hairstreak sipping nectar will likely be my natural history highlight of the year!

White-letter Hairstreak taking nectar, the first time I’ve seen this in 24 years of butterfly watching! Note the white “hairstreak” line has the letter w, however this can also be seen, albeit weakly, in Black Hairstreaks.

Another sighting of nectaring White-letter Hairstreak soon after the previous views. Fabulous to see!

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