In pursuit of purple

A female purple hairstreak butterfly (Neozephyrus quercus) showing the purple streaks on the upper w

A female purple hairstreak butterfly (Neozephyrus quercus) showing the purple streaks on the upper wing. Picture: Sandra Standbridge (Shutterstock) - Credit: Archant

This summer so far has been all about the butterflies for me. On many of my walks recently I have regularly recorded over 15 different species through a mixture of woodland and grassland habitats. None of them have been particularly rare or even scarce but that does not mean I have not had to employ a little patience in finding them! Even some of our commonest wildlife is rarely seen and hunting for it can be as much fun as finding something genuinely rare.

The underwing of a purple hairstreak - photo by Rupert Evershed.

The underwing of a purple hairstreak - photo by Rupert Evershed. - Credit: Archant

Some butterflies are, of course, big and bold and alight conveniently along the path for me to photograph and enjoy - peacocks, ringlets, meadow browns and most recently dancing silver-washed fritillaries on a walk through Symondshyde Great Wood.

I have also kept my eyes peeled for that rare and elusive king of butterflies, the purple emperor, but so far 'he' has eluded me. Formerly extinct in many areas there have been widespread sightings over the last few years and not a few recorded in Hertfordshire this year.

Referred to as 'His Majesty' by butterfly enthusiasts it is not just the purple emperor's size and scarcity that appeal to me but the colour too. Purple in nature is relatively rare and catching a glimpse of purple in the greens and browns of the tree canopy would be something special.

On this front I have, however, met with some success for there is another butterfly that can claim purple to its name: the purple hairstreak. Like much of our wildlife, purple hairstreak butterflies - one of five hairstreak species in the UK - fall into the category of creatures that are widespread and common and yet rarely seen or appreciated. This is largely due to their habit of feeding up high and almost exclusively in mature oak trees.

Finding them requires a lot of neck straining and a keen eye to pick out their small form and fast, flickering flight. Patience is then required to wait for one to land and land in view before training binoculars on it to confirm its identity. I have spent a lot of time scanning oak trees and while I have often found purple hairstreaks I have also been frequently frustrated as they dance out of sight or settle hidden in the leaves.

The satisfaction is therefore that much greater when one finally does land in view, its wings held upright revealing a pale, grey underwing, crossed with a white line and punctuated by an orange 'eye'. But the best it yet to come - if you are lucky - for just occasionally the hairstreak allows its wings to open and there it is: that rare glimpse of purple!

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It is as if the smart grey suit jacket has been flicked revealing a bold flash of lining colour. The upperwing of the males' is dusted purple all over while the females' have just a couple of purple brushstroke-like streaks on each wing. A momentary glimpse is that little bit of something special that makes this otherwise common British butterfly a rare treat and worth looking for.

Surprisingly, neither the purple Hairstreak or the purple emperor butterflies are actually purple - the pigmentation of their wings is plain old brown. The purple we see is a 'structural colouration' caused by the way the butterfly's wing is formed at the microscopic level. The tiny nanostructures interfere with visible light, promoting some colours of the spectrum and suppressing others. The result is that, in good light and at certain angles, we see purple on their wings.

For me this revelation only adds to the magic of the moment for these butterflies are truly little beings of light: not just enjoying the sunlight but part of it as unique little interpretations of light. Next time the sun's out and you find yourself standing at the foot of an old oak tree have a look up and see if you can catch a rare glimpse of purple from this common but little-known butterfly.

We have just one oak in our garden that I planted about 10 years ago. It's still quite young but already twice my height and I hope that one of these years it will attract a purple hairstreak and give me great views from an upstairs bedroom window!