The Swallowtail Butterfly in Portugal

Swallowtail. Photo by Steve Andrews

Just over a week back I was happy to watch a female swallowtail butterfly (Papilio machaon) emerge from a chrysalis that had formed from a caterpillar I had helped rear. It had fed on rue (Ruta graveolens) that was growing in the front garden where I live in Portugal.

I watched this magnificent insect wait until her wings were dried and expanded successfully but it was late in the day and with the early darkness the newly emerged swallowtail had to wait until the next morning before I could release her into the sunlight.

I was surprised to see this butterfly emerge as late in the year as early December, although it can still get warm in the day when the sun is out and other species of butterfly are still flying.

The caterpillar of the swallowtail butterfly feeds on various plants in the parsley family, as well as rue in continental populations but in the UK the larvae will only take milk parsley. 

Swallowtail caterpillar on rue. Photo by Steve Andrews

Fortunately for swallowtails in Portugal the rue is often grown in gardens where it forms large clumps or small bushes.

Swallowtails are very rare Britain and only found in the Norfolk Broads where they live in the fenlands where their foodplant grows. The swallowtail is one of the rarest and largest species of British butterfly.

In recent years the continental swallowtail has been reported in the UK as well and it is thought to have crossed the channel as migrants.