There are some critters that are continually remarkable. No matter how many times you see them, each sighting causes instant amnesia and a declaration of surprise and new admiration. For me, sturgeon and newly emerged Polyphemus moths are like that, but I have a special place for the likes of the Spicebush Swallowtail Caterpillar. This is a creature that hides all the time and rarely moves unless prompted, but oh, how well it is packaged and presented.
In spite of their name, Spicebush Swallowtail larvae can be found on Sassafras trees as well as Spicebush bushes. The female butterflies will lay their eggs equally on both. This probably presented a small problem in the naming department at some point. Folks just couldn’t go around saying things like “Look there’s a Spicebush/Sassafras Swallowtail.” Name simplification was required. Spicebush sounds more exotic and alluring, so that was the name that stuck. I mean, a Sassafras Swallowtail sounds more like some kind of tame Root Beer Drink. A Spicebush Swallowtail, on the other hand, sounds like something that is alcoholic and perhaps even illegal on Sundays in some parts of the country. Fortunately, this swallowtail is not a drink, legal or otherwise, but it is refreshment for the eyes.
Finding the larvae of this species involves a bit of a search. It is like searching through the Christmas packages to find the one with your name on it (What! Only one!). You need to search through the leaves to find one that is folded like a taco (Yes, I know, we don’t get tacos for Christmas but I am on to a new analogy now.) Take a look at the photo above and you’ll see what one of these tree tacos look like. From their very first stages, the caterpillars create these structures as protective shelters. They do this by weaving a mat of silk on the upper leaf surface –an act which eventually causes the two leaf edges to draw together to create a leafy taco. The larvae will exit the shelter to feed and retreat to it when resting or changing skins.
As the caterpillar grows, it creates larger shelters in order to accommodate its increasing size (about 2 inches at maximum size). This means that there will be a series of these tree tacos spread about within the feeding area of the larvae. You’ll need to look in all of them in order to find the resident ‘piller. Since the top edges are not knit together by silk you can carefully slip your finger in the top and force it open. The empty ones will occasionally have a spider inside, so do your duty carefully. Upon opening an occupied shelter you will still jump back a little because the Spicebush Caterpillar is a shocking beast (see below).
Adorned with a double set of false eye spots, the caterpillar looks like a miniature snake. It positions itself within the taco tube so that the fake eyes are facing upward toward the stem. This front door entrance is left open for exit and entry and you could, if you wanted to skip all the package opening, look down into the doorway and see the larvae before opening the shelter (see beginning photo). But, where is the challenge in that!
The pseudo eye spots are there to frighten potential predators. You can get a good sense of that when you first open the leaf (see above). If agitated, like all members of the swallowtail family, the larvae will extend a pair of brightly colored stink horns out of a pouch just above the head, but they are not prone to do so unless really bothered. Once you are over the initial shock, you then have time to admire the rest of the lime-green body adorned with powder blue spots. The lower half of the caterpillar, including the real head, is subtly colored. The bright upper half gets all the attention and I think you’ll agree that it certainly deserves it – again and again (see close up here). By the way, should you find a spicebush caterpillar that is bright orange, instead of green, that means it is in the final stages before pupation.
I have a Sassafras tree in my backyard that regularly hosts these caterpillars and I try to find them there every year. Sure enough, every time I do find one I am delighted and visually refreshed. Call it short-term memory loss or low expectations on my part, but let’s call it what it really is: Nature is a present that continually gives.