Wildlife: The common blue butterfly is thriving in sunny meadows

The former inhabits woods, parks, gardens, and relatively shady places where its larvae feed on shrubs like holly (obviously) but also ivy and garden berberis. The latter on the other hand, frequents open, sunny meadows and pastures with its caterpillars on the pea family such as bird’s-foot trefoil. Whilst both these species are predominantly blue or bluish, and similar sizes, they are easily separated by habitat alone. If you see a silvery-white, blue butterfly in the suburbs, near woodland edge, or flitting through your garden, then it is almost certainly holly blue. This species has a ‘boom and bust’ population behaviour associated with a tiny parasitic wasp, so in a good ‘blue year’ the numbers rise but are tracked by the parasitoid whose numbers follow suit. As the parasitoid rises then the following year the butterfly does badly. However, for the tiny wasp this means its own numbers plummet and so the cycle begins again. The holly blue has two broods each year with a spring and then a later summer emergence of adults, and in a good hot year may have a third brood. The species overwinters as a pupa.

The common blue lives in amongst flowery meadows and can be drawn to a garden with open, sunny borders or grassy areas with abundant flowers. They overwinter as larva, with the caterpillars dropping to the ground where they hide away in dense leaf-litter. This is certainly one of the butterfly species which we hope will gain from changing management of roadside verges and selected other public greenspaces. If this is the case, then look out for them in your garden as well. This does raise a key point about gardening your own patch for wildlife and nature, and that is the need to get the wider area into better condition. If you hope to get butterflies visiting your own butterfly borders, then you also need to look out for and look after the local park or other green spaces.

Professor Ian D. Rotherham, researcher, writer & broadcaster on wildlife & environmental issues, is contactable on [email protected] ; follow Ian’s blog https://ianswalkonthewildside.wordpress.com/