Black Swallowtails: How to Identify Them

Black Swallowtail Butterfly (Papilio polyxenes) Swallowtail Family (Papilionidae). Photo by Donna L. Long.
Female Black Swallowtail Butterfly (Papilio polyxenes). Photo by Donna L. Long.

 

Black Swallowtail butterflies visit my garden often. Just about everyday I see this big butterfly fluttering about two feet above the ground, as it searches among the flower blossoms for nectar or a hostplant. They like zinnias which I try to have every summer in my garden. The wide flat platform of the blossom is a good landing pad for butterflies.

There are over 483 kinds of Swallowtails butterflies in the world with most living in the tropics. The Swallowtail family includes  the birdwings, which are among the largest butterflies in the world.

Swallowtails flap their wings in slow beats, of just a few wingbeats per second. If they aren’t flying over an obstacle, like a fence, they stay just a few feet above the ground. Those large wings enable them to fly rather fast, at least for a butterfly.

The Black Swallowtail (Papilio polyxenes) is a widespread and common sight. It has eastern and western populations. It is also called the American Swallowtail.

 

How to Identify the Black Swallowtail

I often confuse this butterfly with Spicebush Swallowtails and the dark form of the Eastern Tiger Swallowtail. I look for the line of white dots above the blue scales on the hind wings. Only the female Black Swallowtail has those white dots. Neither the Spicebush or the dark form of the Eastern Tiger have the white spots. The Spicebush and Dark Eastern Tiger only have white dots along the edges of their wings. The Black Swallowtail has a double row of white dots.

The female Black Swallowtail looks a bit like a Pipevine Swallowtail, especially the underside of its wings. The Pipevine happens to taste bad. These the Pipevine, the dark form Eastern Tiger, the Spicebush and the Black Swallowtail look very much like.

The eastern population is mostly black with yellow or white hind wing spots. The western population in California is mostly yellow. All of this kind of butterfly have orange spots on the underside of the hind wings.

Across the bottom half of their wings, the butterflies have light-colored spots. The male Black Swallowtail has two rows of yellow spots along the outer hind wing. The female has two rows of white spots along the outer hind wing. Her spots are much smaller. But, the female has a large spots of delicately shaded blue.

 

Black Swallowtail osterium
Black Swallowtail Butterfly flashes its osmeterium. Photo by Donna L. Long.

Defenses

An osmeterium is a fleshy, orange forked scent gland that all swallowtail butterflies larva have. I haven’t gotten close enough to smell this gland but those who have say it emits a foul-smelling odor. I have poked a Black Swallowtail larva and it responded by waving this, snake-tongued gland at me. Apparently it repels ants, and other predators.

See Black Swallowtail Butterfly and It’s Fascinating Behavior

The Caterpillar (The Butterfly Life Cycle)

 

 

Black Swallowtail (Papilio polyyxenes) butterfly chrysalis by Meganmccarty Public domain, via Wikimedia Commons. Swallowtail butterfly family.
Black Swallowtail (Papilio polyyxenes) butterfly chrysalis by Meganmccarty Public domain, via Wikimedia Commons.

Quick Facts

  • Common name: Black Swallowtail, American Swallowtail
  • Scientific name: Papilio polyxenes
  • Family name: Swallowtails (Papilionidae)
  • Range: Eastern North America, MidWest, southwestern region, and southern California
  • Habitat: open areas such as fields, suburbs, marshes, deserts and roadsides
  • Eggs: smooth, pale cream colored sphere with a swoosh of red around its’ middle; laid singly on leaves
  • Larva: yellow-green, bluish-green or whitish-green with black lines between segments
  • Host plant(s): Carrot/Parsley family (Apiaceae) wild carrot, dill, parsley, parsnip
  • Chrysalis: light brown with harness
  • Adult food: nectar, mud or mineral puddling
  • Sexes: Male has yellow spots; female has creamy white spots on the wings
  • Wingspan: average 3.2 inches
  • Flight: lies a few feet above the ground, fast moving

The Key Takeaways

This butterflies are fast fliers and sometimes I don’t get to see the top side of the wings. I look for the double rows of white spots, the yellow spots on the males and the white and blue spots on the female. Just the other day, I all I could make out on a visitor to my garden was the blue spots. Okay, let’s all that one a female Black Swallowtail.

If these butterflies are frequent fliers in your area, make sure you have plenty of nectar and hostplants for them and you’ll be rewarded with Black Swallowtails not just visiting but living and reproducing right in your backyard.

 

 

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