Giant Swallowtails – A welcome addition to our local butterflies

Steve Blight | Jul 05, 2012

Photo: Giant Swallowtail Butterfly  by Ron Hipfner.

A couple of weeks ago, we received a message from reader Ron Hipfner with a photo of a large black and yellow butterfly taken at Little Long Lake north of Sydenham. It was identified as a Giant Swallowtail, a close relative of the Canadian Tiger Swallowtails and Black Swallowtails that are often seen in spring and summer in our area.

What made this sighting special was that Giant Swallowtails are not normally seen around here. However, this is changing. In the past the only place in Ontario that this butterfly was regularly seen was in the Point Pelee area. For reasons that are not fully understood, the range of this stunning insect is moving north. A strong flyer, it has been seen in more recent years throughout Eastern Ontario, including in Prince Edward County, near Chaffey’s Locks and Charleston Lake, all the way north up to Ottawa, and with any luck, it will be gracing us with its presence every year.

The Giant Swallowtail is big -- measuring up to 12 cm (almost 5 inches) across; it is Canada’s largest butterfly. It has broad dark brown wings crossed on the upper side by a diagonal band of bright yellow spots. The underside is yellowish and the tail is broad with a yellow spot in the centre. The caterpillar has a unique way of avoiding predators – it is lumpy and blotchy, and looks a lot like a large bird dropping.

Giant Swallowtail caterpillars eat the leaves of trees and shrubs in the citrus family. This makes the butterfly a pest to orange growers in the southern US, where its caterpillar is known as an “Orange Dog”. However, most landowners in our area would likely have a much more favourable view of the Orange Dog because it eats the foliage of a rather unwelcome plant in these parts – prickly ash!

Northern Prickly Ash is a native plant in the citrus family that grows as a shrub or small tree. It is often found in dense thickets on land that typically has been grazed by cattle. Cows tend to show little or no interest in munching prickly ash, at least in part thanks to its nasty array of sharp thorns. This gives prickly ash a distinct advantage over other plants, allowing it to infest large swaths of land. I’ve been beating back a few patches of prickly ash over the years, but it is a tough customer.

The Giant Swallowtail flies in open woodlands and nearby fields. It is such a large butterfly that it continually vibrates its wings while feeding at flowers so that it does not tilt the blossom. It flies from late May into July with a second generation of adults flying from late July into early September. Hopefully this large and impressive butterfly will find our area to its liking and will get to work on devouring as much prickly ash as it would like!

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.