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Spicebush Swallowtails

Overview

The Spicebush Swallowtail (Papilio troilus) is one of the striking swallowtail butterflies native to Eastern North America. Recognized for its dark blue-green and black coloration, this species belongs to the family Papilionidae. Adults are known for their graceful flight patterns, often seen flitting between plants and nectar sources. The butterfly is commonly found in wooded areas, along forest edges, and in gardens that provide its preferred food sources. Though a common butterfly throughout its range, it is uncommon in areas without its native host plants.

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Description

The Spicebush Swallowtail is a medium-sized butterfly with a wingspan of 3-4 inches. Its forewings are black with distinctive blue-green iridescent markings, while the hindwings are a deep blue with orange spots along the edges. A key feature of this butterfly is its tail-like extensions on the hindwings, which give it a swallowtail appearance. The caterpillar is a light green with black markings and can mimic a bird dropping for camouflage, which helps protect it from predators.

The adult butterfly can be easily confused with the Eastern Black Swallowtail and Pipevine Swallowtail. Spicebush Swallowtails have a missing orange mark on the outside of their wing, and instead have a comet-like blue streak.

Too see the subtle differences, side by side, in the various black colored species, go to the Black Colored Swallowtail Comparison and Identification Guide.

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Host Plants

Spicebush Swallowtail caterpillar host plants include Spicebush (Lindera benzoin), Sassafras (Sassafras albidum), Sweetbay Magnolia (Magnolia virginiana), and the Camphor Tree (Camphora officinarum)

Spicebush appears to be their preferred host plant. I have three different host plant species intermixed on a couple properties, and they have only laid eggs on spicebush.

The Spicebush is a very low maintenance shrub. It gets small flowers in the early spring, grows in full sun to full shade, has red berries in the fall, and can be kept small by pruning.

Plant Natives and they will come - Learn about the SPICEBUSH HOST PLANT.

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Habitat and Range

Spicebush Swallowtails are primarily found across the eastern and southern United States, from parts of southern Canada down to Texas and Florida. They inhabit wooded areas, particularly along the edges of forests, where they can find their host plants. This butterfly can also thrive in urban gardens that provide the host plants. Spicebush swallowtails do not migrate, instead, caterpillars overwinter in the chrysalis stage

Although not considered endangered, due to loss of habitat and host plants, these butterflies (along with most butterfly species) have experienced a a sharp decline over the past 20 years.

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Adults and Flights

Adult Spicebush Swallowtails live for 2-3 weeks. They feed on the nectar of a variety of flowers, mate, and lay eggs on the underside of their host plants.

In the northeast, there are usually two flights per year, while in the south, where the summers are longer, there are three. These butterflies do not migrate. In the fall, caterpillars form a chrysalis and overwinter until spring.

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Spicebush Caterpillars - Leaf Shelters and Instars

A fun thing to observe with the caterpillars is that they fold over leaves to use as shelters. So, it’s very easy to tell if you have Spicebush caterpillars; you simply look for the folded-over leaves. There will be many folded-over leaves per plant if you have them.

1st to 3rd Instars

Once the eggs hatch on the underside of host plant leaves, the larvae eat through the egg and feed on the leaves. Their first three instars (molts) look like small pieces of bird droppings. For added protection, when they emerge, they make a cut in the leaf by eating it, then use their silk to fold it over, creating a small shelter. In the instar image, the 1st instar has almost finished eating a hinge in the leaf so it can fold it and use it as its first shelter.

4th and 5th Instars

As they grow larger, they turn green and develop large eyespots that mimic the eyes of a snake.

The later instars also have a structure called the osmeterium. This fleshy, forked structure is hidden under the caterpillar's skin when it is at rest. When threatened, the caterpillar can extend the osmeterium outward in a display that resembles the forked tongue of a snake. It can also release a foul odor from glands near the osmeterium.

These instars are much larger than the 1st–3rd ones. The caterpillar will roll over an entire leaf for shelter and live there during the day, emerging at night to feed on surrounding leaves.

Camouflage State - The Orange Phase

Shortly before the caterpillar turns into a chrysalis, it undergoes one more change—it enters the Camouflage phase.

This is when the caterpillar stops feeding. Over the course of several hours, it will change from green to orange. This is triggered by a change in molting hormones called ecdysteroids. These hormones cause the green pigments to decrease, while orange pigments become more visible. Besides the color change, other internal changes occur, which prepare the caterpillar to enter the chrysalis phase.

Once the caterpillar turns orange, it will leave the host plant and find a location to form a chrysalis, usually in a nearby leaf pile or on twigs. It is thought that the orange color change helps with camouflage. Since the dead leaves and twigs are brown, the orange color now helps it blend in.

This phase is difficult to see, as it’s very short. Usually, you will see a large green 5th instar caterpillar on a leaf, and the next time you look, it’s gone. This doesn’t mean it got eaten; it simply turned orange and left the plant to form a chrysalis. The orange phase does leave a bit of a mess, so you can usually tell the caterpillar turned orange and left the leaf.

Usually, these caterpillars only travel 10 feet or less from the host plant to find a place to form a chrysalis. What this means is be careful of the leaf litter around the plant; you can easily step on and crush a hidden chrysalis.

Chrysalis

They stay in the chrysalis for approximately 10-14 days, then emerge as butterflies. In the fall, they will stay in the chrysalis through the winter. These times are approximate. I once had a caterpillar form a chrysalis in July, and it didn’t emerge until the following May!

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How to Attract and Support Spicebush Swallowtails

To attract Spicebush Swallowtails to your garden or backyard, plant Spicebush (Lindera benzoin). These easy-to-grow shrubs provide the necessary food for the larvae. Additionally, planting native nectar-rich flowers such as coneflowers and milkweed will help support adult butterflies.

Even the addition of a single Spicebush shrub to your property can kickstart a local population of Spicebush Swallowtails!

I originally planted one seedling in my yard, and that same year a butterfly found it and laid eggs. The tiny plant could hardly support all the caterpillars! The following year I planted three more and most of them had caterpillars. I then added a few spicebush groupings on a nearby property that I'm restoring, and today there is a thriving breeding population of Spicebush Swallowtails in my area-where before, there were none! Plant natives, and they will come!

Learn about the SPICEBUSH HOST PLANT.

Spicebush (Lindera Benzoin) Host Plant:

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Recommended Butterfly Rearing Items:

Note: Raise butterflies for educational purposes only as it's best to leave them on the native plant. If you do raise them, please keep them outside. do not raise them indoors.

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Recommended Wildlife Restoration Books:

These books below are by Doug Tallamy, a renowned entomologist and ecologist, widely recognized as the leading advocate for promoting native plantings in yards to support biodiversity and wildlife conservation.

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