Adventures with Bagworm Moths

The relatively mild weather we’ve been having this fall has been wonderful for hiking. Unfortunately, it’s also good weather for outdoor chores, so I don’t have freezing cold and snow as excuses to let the windows go unwashed. As I brushed off spider webs, I noticed small brown somethings stubbornly stuck to the windows and frames. The objects were each a tiny cluster of dead plant stems formed into a cylinder and glued to the surface with a circle of white at one end.

This jogged a memory, and I thought back to our moth workshop last summer. Kyle Johnson, Minnesota Biological Survey (MBS) Entomologist, found an impressive number of caterpillars and moths for us to learn about in just 24 hours. During that workshop, at the end of July, we spotted one of these little brown cases on the surface of a leatherwood leaf. Kyle explained that they were movable camouflage for the larvae of bagworm moths. I stored that information away for future use.

We spotted this bagworm moth larvae on a leatherwood leaf during the moth workshop in July. Photo by Emily Stone.

The future is here! I snapped some photos of the bagworm cases before scraping them off the windows with my fingernail, and scrubbed the glass clean. As I started investigating the bagworms further, my searches turned up some dire-sounding warnings about how they can defoliate evergreen trees in your yard. The photos of the cases didn’t look quite right, though. Eventually, I discovered that there are two species of case-forming insects sometimes called common bagworms. One has the tongue-twister name of Thyridopteryx ephemeraeformis and is also known as the evergreen bagworm. Although they can be destructive to juniper and white cedar, they are native to North America. The other insect is Psyche casta, also known as the grass bagworm. This matched the cases I found much better! Both types of bagworms are the larvae of tiny moths.

While they don’t seem to cause problems, grass bagworms were introduced from Europe around 1931 and have spread from Boston across southeastern Canada, and as far west as Minnesota. Modern information about them is pretty sparse, but in 1934, when they were new and interesting, Donald W. Farquhar of Harvard University wrote a comprehensive observation of their unusual life cycle.

Farquhar observed the larvae hatching in June and July. Their first act is to spin a silken sleeping bag and then decorate it with bits of their surroundings. Grass bagworms use little straws of dry grass, which also creates excellent camouflage. This stage reminds me of caddisflies, which are unrelated aquatic larvae who also use silk and local materials to build a protective case. In both groups of insects, the cases are distinctive enough to help with identification. I had split open one of the cases after scraping it off my window, and I did find white silk lining the case of grass.

Once protected, the bagworm sticks their head and thorax out of the case to crawl around and feed. Although the evergreen bagworm seems to cause whole trees to turn brown, I think that grass bagworms just skeletonize patches on broader leaves. Farquhar reports that they eat grasses, mosses, lichens, and “other low plants.” He also observed them eating the scale insects who cause beech bark disease out East, and even cannibalizing their peers in a laboratory setting. As with quite a few moth species, they must get all of their eating done in childhood, because the adults have no mouths!

This larval childhood is also when they do their traveling. Sometimes, just after spinning their tiny silk bag, a larva will drop down on a thread and catch a ride on the wind, similar to a spiderling ballooning on their silk. Humans transport them even farther as we move the objects they call home. Even with tiny legs, walking places is an option, too. Full-grown larvae will climb up trees, buildings, fence posts, stone walls, and my first-floor windows to get ready to pupate and go through metamorphosis. Monarch butterfly caterpillars also go through this wandering phase.

According to Farquhar, all of that takes 11 months. The larvae spend the winter under rocks or in the crevices of tree bark. Fresh spring food allows them to grow faster, and by May they are ready to pupate and become adults.

This bagworm moth case still has the exoskeleton of the pupae sticking out one end! Photo by Emily Stone.

Female bagworm moths have no wings. They emerge from their case, hold onto the bag, and in Farquhar’s words, she “liberates the attractant which summons males within perceiving distance.” In other words, she releases pheromones. Males, who do have strong wings, follow her scent upwind and then search on foot to find her. The two mate, and then the female reinserts her ovipositor into her empty case and squirts in about 150 eggs. She closes up the end of the case with white fuzz, then drops to the ground to die. The eggs hatch after a couple of weeks, and the cycle begins again.

Although I’ve noticed bagworm cases before, I didn’t know anything about their life cycle, or why I find their old cases on walls and windows instead of plants. Now I do! So I’m grateful that this warm fall weather allows me to check things off my to-do list.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Fall Calendar is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Cyanobacteria Then and Now

I don’t quite know what to do with myself in this warm fall weather. Shouldn’t we be crunching through snow or at least hiking on frozen ground? Shouldn’t my watercraft all be in storage and my skis be by the front door? Instead, on an afternoon in late October, I found myself on the shore of Lake Namakagon, paddleboard resting at my feet.

Stand-up paddleboarding is a new skill I picked up this summer. I found it useful for navigating swells on Lake Superior, and spent a day exploring the sea caves. Far more often, though, I’d get done with a bike ride, paddle out beyond the weeds and muck at my shoreline, and using the paddleboard as a swim raft, jump in! Even though it was much warmer than the big lake, a dip in Lake Namakagon was refreshing.

But on that October day, the gentle waves that lapped at my toes were bright green. In almost any other circumstance I’d find that color beautiful, but the thick soup of algae made my stomach drop. There would be no refreshing swim.

Blue-green algae blooms are an increasing issue even in wild lakes. I spotted this algae bloom on Crooked Lake in the Boundary Waters Canoe Area Wilderness in late September. Photo by Emily Stone.

I stared at my feet for a minute, deciding whether or not I should even attempt to paddle through the goo. Then a spot of deep red caught my eye. Among the dark gray rocks along the shore was one lovely pebble made of jasper. That lifted my mood just enough to propel me away from shore.

As my paddle created swirling patterns in the green scum, I struggled with finding beauty in such a mess. This, I guessed, was a bloom of blue-green algae. Warm weather, calm winds, and plenty of nitrogen and phosphorus from lawns, farms, and autumn leaves increasingly lead to algae blooms in late summer and early fall.

Days of calm, warm water with plenty of nutrients often lead to blooms of blue-green algae in late summer and fall. These cloud reflections on Lake Namakagon hide a thick, green soup. Photo by Emily Stone.

Algae are the base of the aquatic food chain. They use energy from the Sun to transform carbon dioxide and water into sugar. Tiny zooplankton eat the algae, and bigger critters eat the zooplankton, eventually feeding fish, eagles, and us. Blue-green algae aren’t true algae, though. They are a type of bacteria who invented photosynthesis.

On land, cyanobacteria are part of cryptobiotic crusts, which hold sandy soils in place. As a partner in some species of lichens, they fix nitrogen out of thin air. In the water, though, cyanobacteria are becoming more common, and more problematic. The thick film they form on the surface reduces sunlight to plants below. They can clog water filters. And they sometimes, but not always, produce toxins that are harmful to pets, livestock, and humans.

My thoughts strayed back to the red pebble near the shore. Jasper is a form of mineral-stained quartz that once formed as layers within iron ore. I enjoy finding them because they are part of such a unique story. A story, I realized with a jolt, where cyanobacteria play a leading role.

Once upon a time, and by that, I mean 1.9 billion years ago, the atmosphere was filled with carbon dioxide and methane, and the first inklings of life had only just begun. Volcanic activity in the early oceans, and erosion off the few continents, enriched the water with iron and silica.

Cyanobacteria bloomed in those mineral-rich seas, and they also produced at least one type of toxin: oxygen. Free oxygen wasn’t part of the Earth’s early atmosphere, and it was lethal to the first forms of life. At first, the oxygen reacted with the dissolved iron and silica, removing itself from the water by precipitating jasper and other minerals. When cyanobacteria doing photosynthesis pumped out more oxygen than the minerals could remove from the water, though, they poisoned themselves. Boom and bust cycles of cyanobacteria, plus other seasonal and erosional events, resulted in bands of iron-rich rock with different colors, textures, and thickness. Conditions on Earth have changed so much over millennia that this type of rock may never form again.

Like me learning the new skill of paddleboarding, cyanobacteria eventually evolved enzymes that allowed them to live with oxygen. No longer at risk of poisoning themselves with the element, they proliferated wildly, their oxygen waste sweeping most of the iron and silica out of the ocean water for good. Then excess oxygen, no longer tied up with iron, escaped into the air, and began creating the atmosphere we enjoy today.

It's a little ironic, then, that one of the issues with cyanobacteria on the modern Earth is that when they die, sink to the bottom of a lake, and decompose, they deplete the oxygen that life now requires.

A few days after that soupy paddle, the Halloween snowstorm stirred up the lake, and the red jasper at my landing disappeared. The storm waves also dispersed the cyanobacteria, at least until next summer. Over the course of Earth’s history, these little beings have played many roles. Were they heroes for giving us oxygen? Are they villains for gumming up our lakes? Maybe they are simply one part of a long and complicated story.

From the Wisconsin DNR:

"It’s very helpful for us to receive bloom reports from the public. You can email them to DNRHABS@wisconsin.gov, and please include photos for verification when possible. If you are ever at the Lake Superior shore and see a bloom, please let us know ASAP by email or by  texting Gina LaLiberte, Statewide Harmful Algal Bloom Coordinator and Inland Beach Monitoring Coordinator, at 608-640-7910. We have a rapid response group set up to grab samples from the (usually) very short-lived Superior blooms."

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Fall Calendar is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

In the Dark

The recent Wisconsin Association of Environmental Education annual conference was held at Upham Woods Outdoor Learning Center on the banks of the Wisconsin River. It was a beautiful setting…even after dark! Photo by Emily Stone.

Light from the dining hall at Upham Woods Outdoor Learning Center spilled out, down the hill, under the pines, and onto the bank of the Wisconsin River, where a handful of environmental educators were waiting for a night hike to begin.

I almost hadn’t joined the group. This was the final night of the Wisconsin Association of Environmental Education annual conference, and I had a long drive home the next day. Being sleepy for that wouldn’t be ideal. But it had been years since I’d been on a night hike, and I didn’t want to miss out.

“Have you ever been on a night hike?” asked one of the activity leaders, who were all graduate students at UW-Stevens Point. “Hasn’t everybody?” asked one young woman, who, by way of explanation, told harrowing tales of following her big brother into the dark for numerous childhood adventures. In this organized context, a few of us explained, night hike means something a little more educational…and safe.

I’d become adept at leading night hikes when I worked at a science camp in the redwoods of Sonoma County, California. The combination of few mosquitoes and temperatures that rarely dropped below freezing made being outside at night there far more pleasant than most of my midwestern experiences. Each week, I’d have a new trail group of 15 to 20 fifth or sixth graders, often from a big city. Each week, I’d take the kids on a night hike where we’d spend an hour or so experiencing the night and doing little experiments to highlight animal adaptations to darkness. I loved it. I’d never stopped to consider how the students felt, though.

After a quick introduction in the light of the dining hall, the hike facilitators led us down a trail. The tread was wide and flat, and I relished the chance to practice my old technique of “seeing with my feet” by placing my steps carefully and sensing where the packed trail became soft edge. At a wide spot, we paused and gathered in a circle.

The instructors introduced the idea of predators using their sense of smell to find prey in the dark. Then they passed out little paper envelopes filled with something scented. There were three packets of each different scent, they told us. Our job was to find all of the people with the same scent. No flashlights allowed!

I sniffed my own envelope, and discovered what was definitely a flavor of tea leaves. Maybe vanilla chai? This immediately brought back memories of raiding the tea selection in my camp’s dining hall to freshen up my set of paired scents. Back then, I had explained the activity as male moths finding females by following their airborne pheromones, but it was basically the same.

As I milled around the Upham Woods group sniffing everyone’s packets to find a match, my nose quickly became overwhelmed. This was harder than I expected! I wondered if the tea scents I’d chosen back in the day had been as distinct to the kids as they’d been to me when I was choosing them in the well-lit dining hall?

Flashlights snapped on again as we started moving farther down the trail. My first reaction was to be frustrated. I’d always loved the challenge—and then the awareness gained—from walking without a light. But as the trail grew rougher, and the drop-off grew steeper, I softened my opinion of the lights, and made sure to fall into step near someone who’d remembered to bring a flashlight. Walking in the dark had been a lot easier on familiar trails.

We hiked for a while, making a few more stops before finding ourselves back in the yard of the learning center dorms. We were instructed to partner up, and choose which one of us was predator, and which was prey. Meanwhile, a grad student set up a playing field with orange cones at the four corners and stuffed animals scattered around. The activity facilitator was holding blindfolds.

This wasn’t an activity I recognized, and for a second, a touch of anxiety bubbled up. I was glad to have a friend nearby who I could trust as a partner, but still I worried. What would we have to do while blindfolded? Would I succeed? Would I be safe? And then I wondered—is that how my students felt back in the redwoods? Did I make them nervous with my odd activities that I thought were so fun? In the end, my friend and I came up with a code of chickadee calls for the sighted partner to direct the blindfolded one to pick up the stuffed animals. We didn’t win the game, but our system worked, and we had fun.

As all the night hikers formed a circle to wrap up the experience, the leaders asked us what we’d learned. The science wasn’t new to me, and most of the activities weren’t unfamiliar either, but I still learned something big: empathy. The experience of being in control of a night hike in familiar territory was far different than being a participant in a new place. Next time I lead a night hike, I’ll make sure that my students aren’t quite so in the dark.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Fall Calendar is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.