Black swallowtails raising their young

Black swallowtails mating ©Janet AllenBlack swallowtails mating

Shortly after releasing these butterflies, which I had raised inside, I found them mating.

Black swallowtail egg ©Janet Allen
Fresh black swallowtail egg

This is what the egg looks like when it's first laid. To get an idea of its size, consider that those big green "branches" are the tiny leaves of a dill plant!

Black swallowtail egg ©Janet Allen
Black swallowtail egg before hatching

This egg is three days old and has become quite a bit darker as the caterpillar inside has developed. It will hatch soon.

The dime is there for scale. These eggs are tiny! It's not surprising, though. After all, how big an egg could a butterfly lay?

Black swallowtail caterpillar molting ©Janet AllenBlack swallowtail caterpillar molting

Caterpillars outgrow their skin a number of times. Each stage is known as an instar, and they have five of these stages.

Generally they eat the skin, but the head piece (I call it a "helmet" falls off. In this photo, you can see the old skin on the left and the "helmet" on the right. I believe this is now the second instar. It's still very tiny.

Small black swallowtail caterpillar ©Janet AllenSmall black swallowtail caterpillar

This is a black swallowtail caterpillar when it's still small. (There's the edge of a dime in the photo to give an idea of scale.) It's big, though, compared to the tiny egg it started as!

Black swallowtail caterpillar molting ©Janet AllenThe caterpillar has just finished shedding its old skin

This caterpillar has just molted. You can see the discarded skin at the left trailing out behind him.

Black swallowtail caterpillar molting ©Janet AllenTurning around

It's turning around to face the shed skin.

Black swallowtail caterpillar molting ©Janet AllenEating its old skin

And now it's eating its old skin! Waste not, want not, I guess. It's just one way that nature infinitely recycles things.

I imagine the caterpillar is retrieving nutrients from the skin, but I haven't yet looked into the details about this process.

Notice how its head is still not hardened.

Black swallowtail caterpillars at different stages ©Janet AllenBlack swallowtail caterpillars at some of its different stages

Here are black swallowtail caterpillars at three different stages. Unlike monarchs, which look pretty much the same (though not identical) at each instar (larval stage of growth), swallowtails look a bit different at each stage.

In this case, it's eating parsley, another of its larval host plants.

Large black swallowtail caterpillar ©Janet AllenLarge black swallowtail caterpillar

This is a large black swallowtail caterpillar—about as large as it will get before beginning its transformation.

Getting into the harness ©Janet Allen
Getting into the "harness"

It's always interesting watching how they get into their "harness." They're certainly flexible!

Chrysalis ©Janet Allen
The chyrsalis appears

And, unlike the myth of butterflies making cocoons (unfortunately passed on to our kids with The Very Hungry Caterpillar book!), there is no "cocoon." The skin splits and the chrysalis appears.

Black swallowtail as a pupa - green form ©Janet AllenBlack swallowtail as a pupa—the green form

After a while, the black swallowtail caterpillar becomes a pupa. This is the green form.

Note the "harness" it uses to attach itself.

Each of the kinds of caterpillars I've raised has a different way of going about this transformation.

Black swallowtail as a pupa - brown form ©Janet AllenBlack swallowtail as a pupa—the brown form

Here's the brown form. I didn't know what caused them to become green or brown since it didn't always coordinate with the background color.

Some of the people on the DPLEX listserv (a MonarchWatch forum) suggested that it is the amount of light available: more light, more likely green. And in mid-summer with more light, they are more likely to be green. (See also the Massachusetts Audubon Society's explanation in the sidebar.)

Black swallowtail emerging ©Janet AllenBlack swallowtail emerging

The black swallowtail butterfly emerging


Swallowtails overwintering ©Janet AllenOne butterfly is emerging, and another pupa is attached to the stick at the upper right.

The first year we raised black swallowtails, we collected a second batch of eggs after the first batch was successfully released.

After they became pupae, though, we waited and waited for them to emerge as butterflies. After a few weeks, we knew something was wrong since there was no change.

We did some research and discovered that the last generation overwinters as pupae!

Swallowtail emerging ©Janet AllenSwallowtail emerging after nine months as a pupa!

Now what to do? The best I could figure out was to put them on the screen porch for the winter. Was this going to be similar enough to the kind of environment they would have sought out on their own?

Unfortunately, though I had only four pupae, they were in two separate aquariums. Since one aquarium was smaller, I put it into the larger aquarium and added a cottage cheese container as a spacer so the smaller one wouldn't move around and crush the pupa attached to the wall of the larger aquarium.

I worried about them all winter and occasionally checked on them. What I was going to do if there were some undefinable problem I don't know.

Spring swallowtail ©Janet Allen
A female (more blue) that emerged in the spring after a winter on the porch

Spring came and I watched to see what would happen. It seemed unlikely that these pupae could have possibly survived the harsh weather on the porch, but one day, they just emerged! At that point, they had been pupae for about nine months.

I was glad they survived, but didn't really want to do that again. I vowed to stop collecting eggs after the first batch.

However, the second year it happened again. I didn't think the overwintering generation would start so soon.

A male black swallowtail ©Janet Allen
A male (more yellow) that emerged after overwintering

They again overwintered on the screen porch, and I checked them daily when the temperature started to reach 60°F.

Amazingly, after nine months, including a winter on our screen porch, the first one emerged on May 19. The other three emerged during the course of the following week.

After these successes, I now trust the process and collect the eggs laid in the fall, confident that they'll survive.