This Brown Hairstreak butterfly, which is one of Britain’s rarest and most elusive butterflies, has been spotted on Streatham Campus by one of our Gardeners, Adam.
The Brown Hairstreak butterfly can be found in southern and western England, typically in small woods and among thick hedges. This butterfly has declined rapidly over recent decades and is now listed as a top conservation priority; the reason for the decline is annual flailing and the loss of hedges – over 50% have been removed in the last 60 years in England. The tiny white eggs (around 1mm across) are laid on new growth of Blackthorn twigs and are very susceptible to cutting by tractor mounted flails.
These butterflies are extremely difficult to spot, so finding one requires a lot of luck or patience – often both! This butterfly has brown upperwings and the underwings are browny orange with two white lines streaked across them. Females have a bright orange patch in the top corner of each forewing.
The adult butterflies fly from mid July to mid September but spend most of their time in tree tops where they feed on honeydew, a sweet liquid that is secreted by aphids when they feed on leaves. They rarely come down to feed on flowers, but do occasionally in hot weather or after rain has washed the honeydew off the tree top leaves.