Kicking off our top-ten species, ten day countdown to BioBlitz on Saturday July 7th it's Green Hairstreak ( Callophrys rubi ).
Green Hairstreaks are widespread throughout Britain, although this butterfly has declined in some local regions. They can be seen at rest with wings closed, showing their bright green undersides. And if you've ever wondered about their colour, it's produced by light scattered and reflected from structures on the underwing known as gyroids. These gyroids are orientated in different ways and the overall effect is to scatter green light, a natural example of a photonic crystal. The light from the wings is polarised and since insect eyes are polarisation sensitive, it's thought that this light may produce an invisible signal that might be used in mating in some way. Some Green Hairstreaks will have white spots which form a white 'streak' although this marking is really variable and sometimes almost absent. In flight the Green Hairstreak's upperwings give it a brown appearance.
Another cool fact about Green Hairstreaks is that the pupae, which are formed at ground level, make a squeaking noise ! This attracts ants who in response bury any pupae they find. Green Hairstreaks can be found in a wide variety of habitats, including moorland and are strongly associated with scrub and shrubs. Bilberry is likely to be the main foodplant for Green Hairstreaks at Dove Stone although other foodplants include Bird’s-foot Trefoil, Dogwood, Bramble ( rubi derives from rubus, meaning Bramble ) and Gorse amongst other plants; all of which we also have at Dove Stone.
Males and females look similar but differences in behaviour help with id'ing. Male Green Hairstreaks are territorial; they'll use a favourite spot where they'll wait for passing females and rival males can be seen spiralling in flight together. Females will spend most of their time away from the male territories, searching for nectar and foodplants on which to lay eggs.
Green Hairstreak are on the wing into early July so every chance of seeing this superb looking butterfly at the BioBlitz. A bit of warm weather might also help...!