Papilio troilus troilus

Papilio troilus (Spicebush Swallowtail) is found throughout the eastern half of the US and also ranges into southern Ontario in Canada, reaching as far north as Toronto. Occasionally, this species is seen east of Toronto along the north shore of Lake Ontario. There are two subspecies. Subspecies troilus is found throughout most of its range, and subspecies fakahatcheensis is restricted to the southern tip of Florida. This is likely a relic population from the last ice age, and was only recently described by the late Ron Gatrelle in 2000.

The larvae of this species feed on plants in the Laurel family, mainly spicebush (Lindera benzoin), sassafras (Sassafras albidum), and in the southern parts of its range, red bay (Persea borbonia) along with its close relative, Papilio palamedes (Palamedes Swallowtail). The caterpillars of these two species are very similar and can be difficult to distinguish for the novice. In my area, the dominant food plant is sassafras, and that is where I find most of the ova and larvae. I occasionally find pupa on or near the food plant.

Eggs are cream white and laid singly on the underside of leaves. After several days, a black dot will develop centrally within the egg, which is the head of the small caterpillar inside.

These are 1st instar larvae. Right from the start, these caterpillars build shelters for themselves to hide from predators. They will lay silk strands across the edge of a leaf and use that to pull the leaf upon itself and form a furl. They will rest inside this furl most of the time, and only come out to feed. Recognizing these furls is one of the best ways to find larvae in the wild. Occasionally, caterpillars of other species or even spiders will build similar furls, but after a while, you start to recognize the furls that are characteristic of Papilio troilus.

There are two 2nd instar larvae in this picture. When the caterpillars are small, they are a mottled black and white pattern to mimic bird droppings. This is another way in which they try to fool predators.

This is a 3rd instar larva. In this picture, I have unfurled the furl it was hiding in, and you can see the shimmering silk strands the larva is resting upon. You can also see the beginnings of eye spots, which become more noticeable as the larva grows.

These are newly moulted 4th instar larvae. Again, I have unfolded the furls they were hiding in, and again one can see the silk strands across the leaf. The eye spots can be seen a bit better in these pictures.

This is the 5th instar, or final larval stage before pupation. As with many other swallowtail species, the last instar heralds a dramatic color change. The larvae are now a bright green, and no longer mimics bird droppings. They have two huge fake eye spots to scare away predators. At this stage, the furls made from the edge of a leaf is no longer big enough to conceal them, and often they will fold an entire leaf on itself to form its shelter.

Prior to pupation, it will stop eating and start to change color from green to an a burnt orange. I'm not sure why this happens, as it does make them quite conspicuous. They will also leave their shelter, wander off and usually away from their food plant, and try to find a good spot to pupate. In this above picture, the larva is just starting to turn a bit yellow.

This is what the larva looks like when it has completely changed color. They are quite noticeable crawling on the ground, and this is when most people come across these larvae.

There may be anywhere from two to several generations per year, depending on latitude. The pupae come in two color forms, green and brown, like many other swallowtail species. In most swallowtail butterflies, the green pupae are most common for the summer generations that develop directly into butterflies, while the brown form pupae tend to overwinter and emerge the following spring.

The top two pictures are of the same individual - a female raised this year from a larva. The bottom picture is a wild female nectaring on burdock. The adults are medium to large butterflies that are predominantly black with varying amounts of green-blue on the hind wings. They are thought to mimic the unpalatable Pipevine Swallowtail.

From top to bottom, the above pictures are of males dorsal and ventral, and females dorsal and ventral. The males have more green-blue on the hind wings, where as the females have less extensive but bluer coloring.