Swallowtail Butterflies

Several weeks ago, we had orange and black Monarch butterflies migrating through the Front Range. They seem to have moved on.

But we’ve still got big butterflies in the area — yellow and black swallowtails. I’ve seen two different types of swallowtails. The western tiger swallowtail is lives along waterways and in woodlands, as well as suburban areas. It’s caterpillers eat aspen, cottenwoods and green ash. The eastern version of this butterfly …. hmmm…. lives in the east? That’s all I’ve found to separate the two.

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Western tiger swallowtail on Canada thistle.

The other species of swallowtail that I commonly see in the west Denver area is the two-tailed swallowtail. Predictably, it has two tails.  These butterflies lay their eggs on green ash and chokecherry, although the adults evidently like the nectar from our milkweed plants.

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Two-tailed swallowtail on milkweed.

It’s a hard life being a butterfly. This poor guy has survived a lot.

Damaged two-tailed swallowtail butterfly on milkweed.

Swallowtails lay their eggs on their preferred plants. The eggs hatch out into caterpillers, which proceed to feed on their host plants. When winter comes, these larva spin a chrysalis (cocoon), in which they overwinter.

Unlike Monarchs (Monarch Butterfly Migration) or Painted Ladies (Painted Ladies migrate across North America! Painted Ladies Part Two), swallowtails only produce one generation a season. The adult swallowtails emerge in May and June, and continue to be active in the same area through August, feeding on plant nectar, as the butterflies above are doing. Sometime in the summer, they lay their eggs.

Painted Ladies Part Two

After seeing thousands of painted lady butterflies a couple of weeks ago, I thought they were done for the season.Painted Ladies migrate across North America!

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Wrong! There are still so many migrating through the Denver area, that, when they fly a bit higher, they are visible on radar!

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NWS Boulder‏Verified account @NWSBoulder Oct 4 4/4: Migrating butterflies in high quantities explains it. Today, the butterflies are staying close to the ground. #cowx #Science

How cool is that?

Painted Ladies migrate across North America!

This morning, my husband and I stepped out of our house to walk our dogs, and were mobbed by Painted Lady butterflies! Painted Lady hatch-03

There were dozens in our yard, sipping nectar from sunflowers and oregano.

Painted Lady hatch-05As we walked through the neighborhood, the numbers increased. They were everywhere. Delightful!

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Painted ladies are on every continent except Australia and Antarctica. (Painted Lady Vanessa cardui) Like the much more famous Monarch butterflies, Painted Ladies use multi-generational migrations. They start in Mexico, and take several generations to move into Canada, then turn around and take several generations to get back to Mexico (at least I think that’s how it works…) They do the same thing in Europe, migrating to tropical Africa. Nature Nut: Have you seen the painted ladies ‘invasion’? Nobody knows how they know where to go.Painted Lady hatch-11

They do this every year. Some years, the migration is bigger. And some years, like this year, the migration is enormous.

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Happy to have seen it.