Coastal BC Insects: Pale Tiger Swallowtail Butterfly

Pale tiger Swallowtail Butterfly

The Pale Tiger Swallowtail is another large butterfly common to our coastal region in British Columbia. It's similar to the Western Tiger Swallowtail but has a much lighter appearance.

The Swallowtails appear later than the Mourning Cloaks. My first sighting this year was in mid-May and they stay through late-July.

The forewings are a pale yellow with black edges and bands radiating downward from the top. The hindwings have the distinctive pointed tails, much like the forked Barn Swallow’s tail. Supposedly, the tails evolved as a protective mechanism. If grasped by birds in flight, they will detach and allow the butterfly to escape and survive.

Like most butterflies, it lives on flower nectar. The larvae have more specific dietary needs. Eggs are laid on willow, poplar, sycamore, or alder trees so when they hatch their preferred food is readily available. We have lots of alders in our logging slashes, so that makes them prime Swallowtail breeding territory.

The larvae of the Pale Tiger Swallowtail eat foliage of woody plants then turn into pupa to wait out the winter. Butterflies emerge in the spring to enjoy the sweet nectar of blooming flowers, and start the mating and egg laying cycle all over again.

The males have an interesting behaviour called mud-puddling. They use small puddles and muddy ground to get moisture and nutrients from the damp soil. Recently, I found two butterflies in my garden doing just that. Here's a short video of their dance-like endeavor.

When I took the video I didn't know the purpose of their activity. Now, with a little research I've learned something new about the world around me. Some online resources I use for insect identification include:

E-Fauna BC -- Electronic Atlas of Wildlife in BC Insects and Spiders of BC -- Picture Gallery by Terry Thorman Butterflies and Moths of North America -- includes maps InsectIdentification.org -- includes a handy identification tool Bug Guide -- US and Canada Google -- using an image search 

Have you learned something new lately? -- Margy