I saw this beautiful black swallowtail flutter past me and sit down lightly on the deep pink Moss Campion flower. It slipped its nectar-sucking straw (proboscis) into the little trumpet-shaped blossom to feed. Entranced, I watched it move from flower to flower for a few minutes before I realized I was missing a great photo, so I went in and got my camera. For about half an hour, I followed it around the garden at a respectful distance, sneaking close for a shot when I thought it wouldn't be startled.
What Was Its Name?
At first, I assumed this was a Black Swallowtail; however, when I got my photos back and started comparing the pictures with those in the field guides, I got confused. Several swallowtails are black with very small differences between different species. If you really want to get the right name attached to a butterfly, you have to look carefully at the identifying marks.
On this butterfly, there are two black spots within an orange circle at the tail end of the back wings. On a Black Swallowtail, the black spots are centered, but on a black phase Old World Swallowtail, the black spots are off-center on the side towards the body. As you can see on this picture, the black spots are off-center.
To make identification even more confusing, one of my field guides called this a Western Black Swallowtail (Papilio bairdii). The other guide called it an Old World Swallowtail (Papilio machaon, subspecies Bairdii). I know that sometimes names are changed because scientists get new information about a subject. Therefore, I accepted the name in my most recent field guide: Western Butterflies, a Peterson Field Guide by Paul A. Opler and Amy Bartlett Wright.
Butterflies Never Die - They Just Metamorphose
Metamorphosis - a profound change in form from one stage to the next in the life history of a living organism.
The swallowtail was around the garden for nearly a week, then it disappeared. Swallowtails don't live very long as butterflies, but let's look at the rest of the story. Before it flew into my garden, the swallowtail went through a lot of stages and probably the best place to start is with a small green egg on the leaf of a plant that swallowtail caterpillars like to eat. From that egg came a little worm that was mostly black with some yellow spots and a green patch like a saddle in the middle of its body. It started eating leaves immediately and very soon it grew in size, only as big as it could get inside its skin, because the skin couldn't grow at all. Instead, another layer of skin formed inside the outer one and when it got too big to fit, the outer skin split and the worm squirmed out. Then, it continued to eat and did it all over again about four times. Each time it emerged, it changed color a bit until the worm had alternating green and black stripes around its body with yellow spots on the black strips. Click here to see an excellent photograph of a tiger swallowtail worm that looks quite a bit like the Old World Swallowtail worm.
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