Eastern Tiger Swallowtail

Papilio glaucus

The Eastern Tiger Swallowtail is a very common and conspicuous butterfly of southern Wisconsin. It is replaced farther north with its close relative, the Canadian Tiger Swallowtail.

The Eastern and the Canadian Tiger Swallowtails used to be considered subspecies, and this has resulted in some confusion. Historical data (from the USGS) grouped these two species together, so there is no pre-2000 data available on these species.

Identifying characteristics

Above: bright yellow with broad black stripes; females are dimorphic, some similar to the males and others are black with extensive blue scaling on the hind wings (photos 3 & 4; notice that you can see the tiger stripes on the third photo). Below: similar to the top side, mainly yellow background with bold black stripes; dark females have a shadow of the tiger pattern evident, at least in fresh individuals.

Similar species

The dark female of this species would most likely be confused with the Pipevine Swallowtail, which also has only a single row of spots below but has very distinctive iridescent blue coloration on the hind wings; it may also be confused with the Spicebush Swallowtail and Black Swallowtail, but both these species have two rows of orange spots below.

Above, the black form female of this species has a very thin row of white spots on the upper forewing margin that is easily spotted in the field and is unlike any other black colored swallowtail in Wisconsin. The last photo shows a very worn female that has lost most of her tails, but notice that you can still see the white row of light spots on the forewing with which I was able to identify this species in the field.

The yellow forms can be very easily confused with the Canadian Tiger Swallowtail, but only in central Wisconsin where the ranges of the two species overlap. Additionally, since the Canadian has only a single brood that trails off by August, identification becomes much easier in the late summer and fall.

Eastern Tiger Swallowtails have the following characteristics:

1. the yellow marginal spotband on the front wing below is broken into distinct spots, while in the Canadian these are continuous (unfortunately, some Eastern Tiger Swallowtails do have continuous spots bands); and
2. the broad, black line on the trailing margin of the hind wing is less than half way to the first vein, while in the Canadian it is at least half way to the first vein.

Habitat

Wooded areas and open areas near woodlands.

Flight

Two broods; May/June and then in late July/August. Adults can be found on the wing well into September.

Abundance

Common throughout the southern part of the state.

Locations