The Black Swallowtail butterfly is probably the second best known butterfly, next to the Monarch, in the eastern United States.
In the United States, this butterfly species is found in all states east of the Continental Divide as well as in many of the southern states west of the Continental Divide.
Black Swallowtail butterflies host on plants in the carrot family (Apiaceae) as well as Rue (Ruta graveolens).
We have raised this species on carrots, fennel, parsley, dill, Queen Anne’s Lace, Water Hemlock (deadly to humans), Roughfruit Scaleseed, and Mock Bishop’s Weed.
Although caterpillars will easily change from fennel to parsley and vice-versa, it is difficult to impossible to start feeding caterpillars on plants in the parsley family and move them to Rue. When customers order Black Swallowtail caterpillars from the farm, we must begin them on Rue if our customer is going to feed them Rue.
Male butterflies have more yellow and very little blue on their hind wings. Female butterflies have more blue and very little yellow on their hind wings.
Female butterflies lay round cream colored eggs on their host plants. A day before the egg hatches, a dark ring appears around the egg.
Although eggs are laid singly, the same butterfly may visit the same plant hundreds of times, laying one egg each visit. She touches her feet to the plant and lays an egg. Normally she will continually move her wings and stay in flight as her feet touch the plant and she lays one egg. She lifts off the plant before flying back down to lay another egg.
Both Black and Giant Swallowtail butterflies lay eggs on Rue. Black Swallowtail eggs are cream and smooth. Giant Swallowtail eggs are round and orange or rust colored. Giant Swallowtail eggs have a rough surface.
If you plan to use Rue as a host plant for these butterflies, please be aware that some people have contact dermatitis issues with it. Rue can leave a red or brown burn mark on the skin. It may take hours for the mark to appear.
After hatching, the caterpillar eats its egg shell and begins to eat the host plant.
Black Swallowtail caterpillars go through five distinct appearances while they are caterpillars. At first, a tiny black speck with a white spot on its back is all you notice. Soon, they’re a tiny bit larger and a larger white saddle appears. Soon, bits of yellow/gold add color to the caterpillar. By the time it is a large caterpillar, is it black, white, yellow, green, and orange. The colors from one caterpillar to another may be quite varied.
When a caterpillar is ready to pupate, it may crawl 100 feet or more away from its host plant. Once it has chosen a spot to pupate, it makes a large mat of silk from its spinnerets (under its head). In the midst of the mat of silk, it makes a small tight silk button.
It empties its digestive system with a wet messy glob of frass (caterpillar excrement). Normally their frass is fairly dry. This alarms people who raise swallowtails for the first time. It is totally normal.
It crawls onto the mat and locks its anal prolegs on the silk button. It makes a silk sling or girdle by touching its spinnerets down, moving its head up and over and down, up and over and down, dozens of times. It ducks its head and upper body into the girdle and sits for a day.
The following day, the caterpillar literally splits its cuticle (skin) behind its head and wriggles out of its cuticle. The cuticle slowly moves downward to it’s rear and falls off the new chrysalis. The fresh chrysalis attaches its cremaster (rear end of the chrysalis), covered in tiny hooks, into the silk button.
Over the next hour, the chrysalis slowly reshapes into the classic Black Swallowtail chrysalis shape. Over the next 24 hours, it hardens.
The color of a Black Swallowtail chrysalis depends greatly upon the environment when it attached itself as a caterpillar and pupated into a chrysalis.
When caterpillars are raised in containers, they often choose the same spot to pupate. When they do, one often pupates on top of another. Because of the silk mat they make before they pupate, it is dangerous for the butterfly when one chooses to pupate on top of a chrysalis. It means that the second caterpillar literally sews the first chrysalis shut.
Once both chrysalises have hardened (a day after the second one pupates), they can be soaked with water. After a few minutes, the chrysalises can be gently removed from the rearing container and separated from each other. If they are not separated, the first butterfly will be sealed in its chrysalis and will not be able to emerge.
The day before the butterfly emerges, its tiny wings show through the chrysalis shell.
After emerging, it pumps hemolymph (blood) into its wings and the wings slowly expand into full size and shape. Within an hour, its wings are dry and it is ready to fly away.
If your butterfly emerges indoors and the weather is not acceptable to release the butterfly outdoors, you can keep it indoors for a day without feeding it. Adult butterflies do not eat the day they emerge.