The common yellow or oldworld swallowtail butterfly is a common butterfly which is found across Europe, Africa and Asia. It prefers wet and marshlands as its home and has a life span of up to one month.

This swallowtail is recognizable by its black and light-yellow body with a red-and-blue ‘eye’ print upon its wings. They have a tail-like extension on their hind wings and produce green, black and orange caterpillars. Their wingspan is approximately 3.7 inches (95 mm).

The food the common yellow swallowtail butterfly will eat changes as it transforms from being a caterpillar. As a caterpillar, they only eat very specific plants, most preferably milk parsley although they will also eat carrot, fennel and angelica. When they reach adulthood they mainly exist upon the nectar of flowers. They have a long extendable tongue which they use to drink nectar from thistles and milk parsley plants most commonly.

They mate during the summer, usually from the end of May onwards and they lay their eggs upon the upper leaves of the milk parsley plant. After approximately two weeks the eggs will hatch and the newborn caterpillars are said to resemble bird droppings! As mentioned they develop into larger colored creatures and to warn off predators they have a couple of ingenious techniques. Firstly, they can shoot out a pair of horns from their head to appear threatening and secondly they can produce a secretion which smells so strong it can cause predators to flee. As adults they develop different techniques to keep predators away. The combination of “eyes” on their wings and long tail like appendages confuses predators, mainly birds. This is because the birds can confuse the tail-like appendages with the swallowtails antennae and give them more of a chance of escaping!

Common yellow swallowtail butterflies are becoming less common as the supply of milk parsley decreases. Although they aren’t reliant upon it they prefer to use it to feed, hatch their eggs and many other uses. With the loss of the milk parsley plant, we are also losing the swallowtail butterfly.

This swallowtail is a favorite of butterfly collectors in countries such as England where butterfly collecting is popular.