Scientific name: Polyommatus icarus
The main food plant on most sites is Bird's foot trefoil (Lotus corniculatus). Others used include Black Medick Medicago lupulina, Common Restharrow Ononis repens, White Clover Trifolium repens and Lesser Trefoil Trifolium dubium. Eggs are laid singly on young shoots of their food plants. The caterpillar is small, pale green with yellow stripes and as usual with lycid larvae rather slug-like. Hibernation occurs as a half grown larvae. They are attractive to ants but not as much as some other species of blues. The chrysalis is olive green/brown and formed on the ground where it is attended by ants which will often take it into their nests. The larvae creates a substance called honey dew, which the ants eat while the butterfly lives in the ant hill. In the south of Britain there are two broods a year flying in May and June and again in August and September. Northern England has one brood flying between June and September. In a long warm year there is sometimes a partial third brood in the south flying into October.
Information and photograph courtesy of Wikipedia