Raising Swallowtails: From Egg to Butterfly

I had so much fun raising Monarch butterflies for an outreach event a couple months ago, I decided to repeat the process with another type of butterfly- the Anise Swallowtail (Papilio zelicaon). Since the last of my butterflies emerged today, I thought I’d take another brief break from bees to show some photos I took while raising my butterflies.

Four Anise Swallowtail caterpillars at different stages of development. Believe it or not, these are all the same species!

Four Anise Swallowtail caterpillars at different stages of development. Believe it or not, these are all the same species!

adult top

Like the Monarch butterfly, Anise Swallowtail caterpillars specialize on a particular group of plants in the carrot family (Apiaceae). The adult butterfly is the only life stage that can fly and move quickly. Adult females lay eggs on the appropriate host plant, in this case, fennel or parsley, because the young caterpillars won’t be able to leave and search for new plants on their own.

I found a couple of young caterpillars on a wild fennel plant growing in my neighborhood, and another two eggs that happened to be laid on my parsley plant:

eggs new

Young eggs are small and yellow, and turn brownish as they mature.

eggs new use this

After a few days, the eggshells turned clear and the caterpillars were about to hatch. The photo doesn’t do it justice, but the eggs were a very pretty opalescent color, like tiny black pearls:

eggs late

The tiny newly-emerged caterpillars ate the eggshells as their first meal then began to munch on the parsley. The hole to the right of the caterpillar is where the egg used to be.

brand new larva

Because the caterpillars are not necessarily as toxic as the Monarch caterpillars, they have other defenses. The younger stages (instars) disguise themselves by looking a little like bird droppings.

larva 3

middle instar larva

late instar larva

As the caterpillars get older, they start to develop a different coloration pattern (caterpillars grow by shedding their skin, so they are able to change how they look when they molt).

late instar larva 2

late instar side

The older caterpillars look almost nothing like the younger ones, but they still have a special defense from predators. When disturbed, they rear their heads and exude yellow horn-like protrusions called “osmeteria:”


This is called a “startle defense.” It “frightens” potential predators into looking for another meal.

At this stage, the caterpillars are absolutely voracious. I had to get new fennel almost every day.

After a couple of weeks, the caterpillars search for a place to pupate. When they find a place, they attach themselves by a silk strand and prepare to pupate.

getting ready to pupate
They can travel some distance to find an appropriate spot- I even found one in my bag across the room!
caterpillar getting ready to pupate in bag

Fresh pupae can still startle predators by jerking around in their pupal case if disturbed:

The chrysalises can be a variety of colors from green to brown. I don’t know what causes the different colors, but I imagine that they are these colors in order to blend in with their surroundings so as not to be visible to predators.

green chrysalis

green chrysalis

brown chrysalis

brown chrysalis

The chrysalises were not at all smooth and jewel-like as the Monarch chrysalises were. Instead they had some very interesting textural patterns on the surface:

green pupa texture

green pupa close string

After a couple of weeks, the adult butterflies emerged from the chrysalises. I wasn’t lucky enough to catch the eclosion process, but here are some photos I took of the brand new butterflies:

Freshly eclosed adults take time to develop wings and fly away.

Freshly eclosed adults take time to develop wings and fly away.

face portrait

head top


wing closeup yellow

wing red


6 responses to “Raising Swallowtails: From Egg to Butterfly

  1. You ARE having fun! Beautiful pictures!

  2. WOW! Those are amazingly descriptive and gorgeous.

  3. So gorgeous! Yes indeed the eggs look like pearls – they reminded me of the pearls found in the Philippine seas. Beautiful chronology of the beautiful life.

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