Tiger swallowtail

In addition to orange hawkweed, tiger swallowtails visit many kinds of flowers like this daylily while gathering energy-giving nectar. All butterflies are important pollinators, collecting pollen on their legs and body and transporting it to other flowers as they search for food. Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma to allow fertilization. Most flowers, including those that produce food, depend on pollination to reproduce.

While mowing our lawn, I decided to leave a small patch of orange hawkweed that was beginning to bloom. Orange hawkweed is an invasive species introduced from Europe. It is a perennial plant extensively found all over the north in pastures, forest openings, abandoned fields, along roadsides and especially in disturbed and poor soils. It is considered a noxious weed in some places.

The name “hawkweed” was coined by a Roman naturalist who thought that hawks eat this plant to improve their eyesight, but I have never seen hawks eating hawkweed! Have you? Orange hawkweed is also known as “devil’s paintbrush” due to its brightly colored flowers. The flowers are quite beautiful upon closer look.

Anyway, the un-mowed patch of hawkweed I left produced lots of brilliant flowers that were visited by Canadian tiger swallowtails, not just momentarily, but for hours at a time and for several days. That allowed me to get some excellent photos and video while they searched, what seemed like every flower, to get every drop of flower nectar from this little patch of “habitat” I left. This experience showed me once again, that it does not take much habitat to attract interesting species to one’s yard and that invasive species sometimes do provide suitable habitat for some native species like tiger swallowtails.

I always look forward to the time of the year when Canadian tiger swallowtails are out and about feeding on nectar in our flower gardens and on Labrador tea flowers in our black spruce/tamarack swamps. They always seem to be in the swamp when the mosquitoes are at the worst from mid-May to mid-July.

Some confuse the Canadian species with the Eastern tiger swallowtail found in the southern part of the state. They are cousins, but the Eastern species is larger with more yellow above and the light-yellow band along the trailing edge of the forewing is broken up by dark veins whereas the Canadian has a continuous yellow band. Where the two species overlap, they may breed and produce hybrids, just to confuse things.

The Canadian tiger swallowtail produces one brood each summer of green caterpillars that have two mimicking eyespots that may help scare away potential predators. The caterpillars feed mostly at night, another way to protect themselves from daytime bird predators. They favor feeding on willows, birches, and quaking aspen. Adult caterpillars overwinter as a chrysalis that develops through the miracle of metamorphosis into a beautiful tiger swallowtail the following spring when the life cycle begins all over again.

So, who would have thought we would have to be concerned about tigers in our Northwoods?

Nicholls can be reached at nicho002@umn.edu.