It’s intriguing when a host plant is so important to a species that it’s named after it! It’s like the old “Who’s buried in Grant’s tomb?” joke: Where does the spicebush swallowtail lay its eggs? On a spicebush!
It can also, however, use a few other plants in the Magnolia (Lauraceae) family such as sassafras and tulip tree.
We had planted five spicebushes, partly for their fat-rich berries that support birds on their migration, but also because we had hoped for spicebush swallowtails. I looked in vain each year for the telltale signs of rolled up leaves that might conceal a spicebush swallowtail caterpillar, but didn’t see them.
Then in August 2016, I spotted a female laying eggs — but not where I had been looking up in the plentiful leaves at eye-height, but on the 2- to 3-foot tall spicebush seedlings that had sprouted up! We hadn’t eradicated them since I had planned on digging them up for our HGCNY native plant sale.
I left some eggs on the plants, but brought a few in to raise. We were treated to a different sequence of growth from the others we have raised (monarchs, American ladies, and black swallowtails).
The just-hatched spicebush swallowtail caterpillar, as with other caterpillars we’ve raised, starts by eating its eggshell. Nothing goes to waste in nature!
Unlike some other butterflies, such as the monarch, each caterpillar stage (called “instar”) looks quite different.
As with other swallowtails, the spicebush swallowtail caterpillar has an “osmeterium” that it wields when threatened. It emits a foul odor.
Not all caterpillars, though, have these scary-looking snake eye markings, though!
The caterpillars also protect themselves by hiding in a folded up leaf they create by laying down silk, which then folds the leaf as it dries. The youngest caterpillars first cut a portion of a leaf tip so the folded part is small.
The shelter isn’t foolproof, though!
One year (2021) we had quite a few spicebush swallowtail caterpillars that had created their own folded leaf shelters, BUT that didn’t stop a wasp that systematically ate each one! This was especially sad because we don’t often have spicebush swallowtail butterflies finding our yard’s spicebushes. We’re an island in an ocean of lawns, pesticides, and non-native ornamental plants.