Caterpillars munch on:
Adults take nectar from a range of flowers including:
This butterfly spends the winters as a caterpillar. In the autumn, caterpillars crawl down the foodplant and find shelter under a leaf, or amongst nearby moss or leaf litter. They’ll stay there for five or six months, emerging in March the following year to carry on growing as a caterpillar.
There is even more about this species on the main Butterfly Conservation website
Like most of the Blue butterflies, caterpillars of the Common Blue produce a sugary substance called honeydew, which is attractive to ants. It allows the ants to feed on it, in exchange for protection from predators.