Swallowtail butterflies take flight

Rob Zimmer
Special Contributor
August is swallowtail season across Wisconsin and you can find several species taking flight as this year's broods begin to reach adulthood.

In constant motion, swallowtails dance across the fields, prairies and gardens of Wisconsin during August. The distinctive flight of these massive butterflies is unmistakable, their wings constantly pulsing or flattering as they travel from flower to flower seeking precious nectar.

August is the peak month of activity for most of our swallowtail species and it is possible to see several varieties as they go about their lively dance.

Unlike the monarch, swallowtails are not migratory butterflies. Their entire existence is spent here where they are born and transform. Swallowtails are found in all areas of the state, with a few additional species being  found in southern counties.

The summer dance of Queen Anne's lace as it billows against the summer sky draws the beautiful black swallowtail. This, our most common swallowtail, hosts solely upon members of the carrot family. This includes Queen Anne's lace as well as wild parsnip, parsley, dill, celery and other related plants. 

Black swallowtails are colored the richest black with metallic blue highlights and rows of golden spots.

Our other common swallowtail species is the tiger swallowtail. One of our largest butterflies, reaching 4 to 5 inches across, this species is a bright, golden yellow with telltale black tiger stripes arranged vertically on the wings.

Many outdoor lovers are surprised to learn that tiger swallowtail caterpillars host in the treetops upon some of our most common deciduous trees. Willow, black cherry, aspen and others are a few of the many trees this species will utilize as a host plant. 

There are two main flight periods for 
tiger swallowtails here in Wisconsin. The first generation emerges in late May or June, flying for a few weeks before a lull occurs during July. The second generation emerges from late July through August, feasting upon a bounty of late-season nectar plants as they mate and lay eggs for the next generation to come.

One of the most spectacular and rewarding butterflies to observe in Wisconsin is the giant swallowtail, with a wingspan that may reach 6 inches across. 

Colored a rich, chocolate brown with gold and yellow lightning flashes across the wings, the giant swallowtail is an incredible winged wonder. 

Over the past several decades, the population of giant swallowtails in Wisconsin has steadily expanded north. It is now possible to see these butterflies during the summer season as far north as Green Bay, Shawano and Wausau. Previously, giant swallowtails were only rare visitors to the southern counties.

It appears this may be due to the expanding colonies of prickly ash, a spiny shrub that serves as the host plant for this incredible beauty. As prickly ash invades more and more terrain, reaching deeper into the heart of the state, the butterfly's expansion may continue.

The swallowtails of summer take wing, thrilling those able to observe these beautiful butterflies in all their winged glory. 

Attract these summer beauties to your yard and garden by planting a variety of late summer nectar plants such as ironweed, Joe-pye weed, cardinal flower, asters, liatris and others.

Planting members of the carrot family, you'll also enjoy the beautiful transformation of black swallowtail caterpillars into their winged adult form. These caterpillars, although they feed upon the greens, do not inflict enough damage to be considered a pest and should be left alone to complete their transformation.

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August is swallowtail season across Wisconsin and you can find several species taking flight as this year's broods begin to reach adulthood.
One of the most beautiful butterflies found in Wisconsin, the Giant Swallowtail has a wingspan that may reach 6 inches across.