Butterfly eggs - Brown Hairstreak

07 April 2021 | Posted in Charlotte Owen , Wildlife
Butterfly eggs - Brown Hairstreak
Brown Hairstreak Butterfly © Ryan Greaves

Brown Hairstreak eggs look like miniature white sea urchins. 

Each one is as tiny as you might expect, measuring just 0.6mm in diameter, and on a sunny winter's day they can appear to sparkle in the light. The eggs are designed to withstand the harshest of winter conditions and shelter the developing larvae within, which spend up to eight months inside their armoured shells. 

Brown Hairstreak Egg©Glenn NorrisSussex Wildlife Trust

© Glenn Norris

They are dormant for much of this time, surviving the winter in hibernation, but by late April the tiny caterpillars will be ready to eat their way out and begin feasting on the Blackthorn's budding leaves. 

Blackthorn©Barry YatesSussex Wildlife Trust

After a month or two of munching they will pupate and eventually complete their metamorphosis in late July, emerging as beautiful brown-winged adults, their undersides a spectacular orange patterned with delicate white lines. 

These are the last of the season's butterflies, winging their way into early October, and their numbers peak just as most other butterflies are dwindling. They are also the most elusive, flying high in the canopy or hidden within hedgerows, and adults are so rarely seen that egg hunts are the only reliable way to monitor the Brown Hairstreak's distribution.  

Sussex is one of the best counties in Britain for this nationally scarce species.

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