Brown argus butterfly
The pretty brown argus butterfly is rarely seen in large numbers on the Commons. Usually only one or two individuals are spotted making them one of the site's most elusive butterflies.
Their wings are mostly dark brown although if you catch the light just right you can sometimes see a lovely blue sheen. They're fringed with white, with a row of distinctive orange spots running along the edges.
The brown argus loves limestone grasslands but it isn't a great wanderer and only travels a couple of hundred metres from where it emerged. They prefer areas that have been well grazed by the cattle. The Bulwarks is an ideal place to see one flying low to the ground. If you're lucky you may find one perching or feeding on flowers.
Like some of the other butterflies on the Commons, the caterpillar of the brown argus has a rather unsual relationship with ants. As the caterpillar grows and gets bigger it produces a secretion that's irresistible to the ants on the Commons. When it turns into a chrysalis the ants carry it away and bury it underground, where it's safe from predators.