18.07.25 Common Blue Butterflies

It’s good to see lots of butterflies this year on the wildflower meadows here and in the garden generally; due to the prolonged warm, dry weather no doubt. In spring, sadly, there were no Orange tips. But now there are plenty of Commas (particularly), Red admirals, Small skippers, Meadow browns, and Gatekeepers.

We have seen noticeably more Common Blue butterflies (Polyommatus icarus) than in previous years. Thankfully they are still common and widely distributed throughout the U.K., and are probably also the most common of the Blue butterfly species in Europe, extending right across northern Asia. They are found in almost any open, grassy habitat and come into gardens very often, of course. Adults appear in June – July and there is usually a second brood in August- September.

Males are obvious with upper sides to the wings being bright blue or blue-lilac all over, and are very visible chasing each other around territorially. Females are more unobtrusive. They keep a lower profile while looking for suitable plants to lay their eggs on so that the caterpillars can eat well. Also, in southern England at least, they have mostly brown wings with only just a hint of blue and some orange spots.

So we probably don’t notice them nearly as much as the males. The female could be confused with the Brown argus butterfly (Aricia agestis), but this has more extensive and prominent orange spots.

Bird’s-foot trefoil (Lotus corniculatus) is the best food plant and there is plenty of that around in the Front and Back wildflower meadows. But many other Leguminosae are also used: Vetches, Clovers, Medicks, Trefoils etc. Common blues spend the winter in vegetation fairly low down, near the ground as a half-grown caterpillar, or larval form. It is small, greenish, and slug-like.

A “honeydew” substance is secreted that attracts ants and can induce them to carry the larva into their nests where it gains protection. This is more characteristic of other Blue butterfly species such as the Large blue (Maculinea arion), but it has been found to happen with P. icarus too, apparently. To encourage Common blues to successfully breed in our wildflower meadows it would seem that leaving patches of Bird’s-foot trefoil intact or mowing only halfway down might be worth trying?

Anthony.heys@sky.com