Friday, August 21, 2015

Those Sneaky Spicebush Swallowtails

Not a bird dropping, but a sneaky Spicebush Swallowtail caterpillar, exposed!

Recently, it’s been taking me a long time to get home from work most evenings. It’s not that I’m running into a lot of traffic or other typical delays. No, it’s that the path I take back to my car is lined with native Spicebushes. This summer I finally figured out how to ID them when they’re not in flower, plus I learned the sneaky trick that Spicebush Swallowtail caterpillars use to avoid being spotted. So of course I have to check every spicebush, every branch I can reach, nearly every leaf, on my way back to the car. I’m looking for folded-over leaves, or just small sections of leaf that have been folded longitudinally to make a shelter for (I hope) a tiny Spicebush Swallowtail Caterpillar. It’s a bit like a treasure hunt every evening!

One of the many Spicebushes (Lindera benzoin) near where I work in Maryland.The ones along this trail are about six feet or so tall and wide, although they can get twice that size. Ovate leaves are alternate, and lots of oval berries sprout along the branches.

Here's a closer view of a Spicebush branch, showing the many berries. They're green right now, and turn red when ripe.


A Gift With A Bonus

This all started with a gift from my boss: a small potted Spicebush that came with a bonus: a caterpillar already in residence. My boss had bought several bushes for his yard and ended up not needing them all. Most had already been visited by breeding Spicebush Swallowtails, who depend on  spicebush as their larval host plant. Knowing that I love raising caterpillars, he offered one of the extra bushes to me.
A folded leaf containing my new Spicebush Swallowtail caterpillar. The caterpillar makes this shelter by laying silk across the leaf, so the sides will close up as the silk dries out and shrinks. Pretty crafty!

I brought the bush and caterpillar home, and over the next few weeks raised the caterpillar to a butterfly. By the time I released the adult butterfly, I was hooked on my second caterpillar species. I was having so much fun, I forgot to even take photos as the caterpillar grew up.
Gleefully releasing my first-ever Spicebush Swallowtail. The branch inside the cage is spicebush that I'd hoped would be a pupation site, but of course my caterpillar decided to adhere to one of the cage walls instead. It worked out though!

I’m currently in between generations of Black Swallowtails, so my caterpillar craving has gone unanswered for a while. It seemed like Spicebush Swallowtails might make a good supplement to the Black Swallowtails.

Now everywhere I go I’m checking spicebushes for the tell-tale leaf shelters. Spicebushes are native and grow throughout the eastern United States, so I'm seeing a lot of them anywhere I hike. I did actually find one tiny caterpillar while I was visiting my mom in Ohio a few weeks ago. (I was too excited to remember to photograph it, though!)

Extra Defenses

I mentioned that the caterpillars hide by rolling up in leaf shelters, which is cool enough. What’s even more amazing to me is that they only come out to eat at night. Before this summer I had no idea there were nocturnal caterpillars! While I was raising the one I got from my boss, after sunset I’d sneak into my now-dark home office and flip on the light to surprise the caterpillar and catch a glimpse of it. As I mentioned, though, I neglected to photograph the caterpillar as it changed over the days.
I peeled open the leaf shelter to photograph the caterpillar when I first received it. Surely I'm not the only one who thinks the newly forming eyespots are kind of adorable!

The caterpillars also have special disguises just in case they get seen: the early instars are bird-dropping mimics, like many other swallowtail species. Later instars have these really cool fake eyes that make them look like tiny fierce snakes. They hide inside their leaf shelter with their head pointing up so the snake eyes will look back at any predator smart or curious enough to peek inside the shelter. Yikes! As you see in the above image, my caterpillar was a middle instar that had both the bird poop camouflage and fake eyes starting to show, complete with false light reflection. Pretty cool.

Since I didn't photograph my caterpillar in later instars, here's one taken by Hagerty Ryan, U.S. Fish & Wildlife Service [Public Domain], via Wikimedia Commons. Those eyespots have gotten much more prominent!

I Have Hope           

So I’ve spent a lot of time over the past few weeks looking for these awesome little critters. But I haven’t found any others besides the one in Ohio. I have found many other tiny things hiding in similar leaf shelters, however: mortally offended spiders as well as a terrified tree cricket, for example. I’ve also found lots of empty leaf shelters whose caterpillars have long since moved on, and I’ve seen tons of nibbled leaves that give me hope. I’m sure not all the nibbling is done by Spicebush Swallowtail caterpillars, of course, some is also done by beetles and other hungry insects. But I have been seeing a lot of adult Spicebush Swallowtails flying around Brookside Gardens lately, nectaring on the many flowers in bloom. So there must be caterpillars eventually, right?
Adult Spicebush Swallowtail nectaring on Cardinal Flower (Lobelia) at Brookside Gardens, in Wheaton, MD.

For that matter, there must also be eggs at some point. The Spicebush Swallowtail’s eggs are usually laid on the underside of spicebush leaves, and are very pale so they blend in. Yet another piece of evidence of the sneakiness of  these canny creatures! Honestly, I don’t even bother to look for eggs on the spicebushes, they are so well camouflaged I feel like it would be hopeless unless I actually get to watch the butterfly oviposit.
Three tiny white eggs on the pale underside of Spicebush leaves. Photographed at the Wings of Fancy Live Butterfly and Caterpillar Exhibit at Brookside Gardens, Wheaton MD (see below for exhibit details). The red ribbon is added by staff to call attention to points of interest like small caterpillars and eggs. Look to the right of the ribbon to find the eggs, if you don't see them at first!


Still Searching

For now I’ll just keep looking for the hidden Spicebush Swallowtail caterpillars, and keep coming home late for dinner. It’s a good thing I’m using my slow cooker a lot this summer, I’ve already started the meal eight hours ago and I know it will be done whenever I get home.

Have you ever spotted Spicebush Swallowtail caterpillars in the wild? Leave a note in the comments if you have! If I manage to find another one I’ll remember to take a picture this time to share with you all. But even if I never find another caterpillar, I’m still enjoying the daily treasure hunt. It’s a very peaceful, mellow way to wind down after work. I hope you too have a chance to see the tiny hidden things in nature, no matter how sneakily they might be disguised.

If You Want To Visit Wings of Fancy

If you're interested in checking out the Wings of Fancy exhibit for yourself, it runs through October 25, 2015. Normally it's May through mid September, but the schedule is different this year. The exhibit is at Brookside Gardens in Wheaton, MD, and is open seven days a week from 10:00 am to 4:00 pm. Tickets are $8 per adult and $5 per child age 3-12. You can purchase your tickets at the gift shop in the Conservatory. Please keep in mind that parking may be limited at the moment; consult the Brookside Gardens web page ( for any updates or for suggested parking alternatives. The street address for the Conservatory and the exhibit is 1500 Glenallan Avenue, Wheaton, MD 20902.

I personally think one of the best things about the exhibit is the Caterpillar House, where we have various larval hostplants with eggs and/or caterpillars on them, as well as a special container for chrysalises once the caterpillars get to the wandering stage. The species in the Caterpillar house change periodically, but are always North American native species. It's so cool to see the caterpillars up close, plus the display also has photos of each caterpillar species in adult form.

The Conservatory (where Wings of Fancy is located) often gets very hot in the summertime, as it's a greenhouse. But this year with the later season I'm hoping we get lots of comfortable cooler days to enjoy the exotic butterflies. I hope you get a chance to visit too!

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