Stories of Scale

I’m not sure why the small, brown bump on the twig caught my eye. I think I was reaching down to pick up my backpack after having extricated myself from the bushes where I was attempting to get a photo of a cute mossy stump. This hike on the North Country Trail had started to feel a little like whiplash. I was motivated to hike fast in the cold, damp weather, but neat things kept catching my eye.

First it was the most elegant scat I’ve ever seen. Pure-white fur cascaded down a mossy stump, its arrangement clearly indicating its origin. Any mucky parts had washed away in the thaw. I wished well to the spirit of the snowshoe hare, and to the belly of whichever weasel that ate it.

Next I spotted a tiny mound of dirt and dried leaves, pushed up in the middle of the path. The earthworms must have been active during a thaw! I shook my head at this invasive species, and gazed forlornly at the forest. A carpet of dingy green Pennsylvania sedge with few indications of tree saplings, and little hope for spring flowers, stretched out under the deciduous canopy. Here was a classic example of a worm-eaten forest.

Mushrooms, woodpecker holes, evergreen wood ferns, leaf molds, and cracked ice also called to my camera before the lens settled on that last moss-covered stump. And then, those small, brown bumps on the twig. How did I ever spot those?

The size, coppery color, and slight sheen of the bumps closely resembled the ironwood tree’s own buds, but the bumps were scattered along the twig. One brushed off in my gloved hand, and I discovered white fuzz inside the little hollow dome. Its former place on the twig was marked by a faint spot of white residue. After snapping a few photos, I moved on. But the mystery bumps kept ‘bugging” me. Who made them?

A friend suggested scale insects, and that had been in my mind, too, although I realized I couldn’t even tell you exactly what a scale insect is. As it turns out, their life story is pretty fascinating, and—typical of insects—a little weird.

The little brown domes I found affixed to the twigs may have belonged to sub-adult females, but from the looks of them, females that didn’t survive. On one shell I noticed a pencil-point hole: the telltale sign of a parasitic wasp escaping after doing its (very important) dirty work. Another possibility is that these scales had simply matured and reached the end of their natural lives.

What are their natural lives? When successful, female nymphs overwinter on twigs. In the spring, if all goes well, they will finish maturing and then lay eggs (sometimes more than 1000 of them!) with or without the help of a flying male. The eggs are laid underneath the protection of their mother’s stationary shell, and the female herself then dies and dries. The eggs hatch about ten days later, and small, yellowish “crawler” larvae migrate to leaves. At this stage, the crawlers might be blown by the wind or even transported on the feet of birds to new locations.

Like their relatives the aphids, the scale larvae insert sucking mouthparts (called stylets) into the plant and start drinking. In order to get enough nitrogen, they must drink an excessive amount of the sugar-rich sap, which they excrete as “honeydew.” Ants take advantage of this just like they do with aphids, and can often be seen drinking honeydew off the scale insects.

As the nitrogen and sugar fuel their growth, the scale larvae molt. With each molt, their bodies become larger and their legs become smaller. Finally, in late summer before their legs completely disappear, the nymphs walk back down the leaf stalk and onto their winter home on the twig. They build their waxy, protective shells, and do not move again. Spring brings maturity, reproduction, and death.

Males do occur, but their larvae and nymphs are flat and nearly transparent. Adult males are tiny, winged, and have no eating mouthparts.

I can’t even begin to tell you what species of scale insect these might have been. After starting my research, I wished that I’d looked under more scales and brought some home, too. Apparently, the variation in appearance within a species of scale is sometimes greater than the variation between different species. Some species only feed on one or two host plants, but many other species are generalists. There are both “armored” scales and “soft” scales with slightly different life histories. Occasionally, outbreaks of scale insects can damage trees, but they are not always a problem.

Whether it’s hairy scat on a mossy stump, worm castings in a lawn-like forest, or tiny brown bumps on a twig, every bit of the world tells its very own story if we’re able to listen.

Special Note: Emily's book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at http://cablemuseum.org/natural-connections-book/.  Listen to the podcast at www.cablemusum.org!

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: "Better Together--Celebrating a Natural Community" will open on May 3!

A Thirst for Nature

As my car came to a rest in the driveway and the engine noise faded, I took a deep breath of relief and opened the door. The blast of frigid air was refreshing after the suffocating warmth of the heater. Leaving my week’s-worth of travel debris in place, and not bothering to dig for my mittens, I quickly zipped my jacket and balled my hands into the pockets.

A desire had been rising up in my chest like a great thirst, but I’d been drinking tea to stay awake for the past seven hours. The thirst wasn’t for liquid, it was for nature. My driveway did not disappoint. I drank greedily from the fresh air, hemlock boughs, rough bark, and mossy stumps.

In the wee morning hours, a fresh dusting of snow had cleaned up the forest. Now I greeted a dainty string of fox tracks as if the owner were still attached. I’ve watched those little paw prints tripping along the driveway so often that sometimes I disregard the fact that they were made by a live animal. I assign a personality--a life—to the embossments themselves. Not only that, but I count the string of charming hollows among my friends. On other days, though, I try to follow the tracks into the mind of the fox and listen to the music playing there.

“All night under the pines the fox moves through the darkness with a mouth full of teeth and a reputation for death which it deserves.” Writes Mary Oliver in her poem, “Fox.”

Walking slowly next to the tracks, I breathed deeply and gazed into the tree canopy, admiring the graceful arc of branches and the lacy friendship of twigs. I think this is what the Japanese mean by shinrin-yoku or “forest bathing.” I certainly felt my mind cleansed and my body refreshed. With every breath, stale air and tension released and peace flowed in.

You may wonder what made me so thirsty for the woods. It was vacation of all things! A trip south (to central Iowa) to see oodles of wonderful, lovely, long-lost family. For the first day, I brought two tubs of MuseumMobile props. In the suburban second grade classrooms, eager fingers (include those of my niece and nephew) explored wolf canines, beaver incisors, and deer antlers. As we compared herbivores, carnivores, and omnivores, the kids giggled at rubber replicas of animal scat before using their key to identify which species dropped which load. When I brought out the soft furs of coyote, skunk, and cottontail, the little hands could not refrain from grabbing. I got the sense that they, too, were thirsty for nature.

After school let out, we took a brisk walk down to the shores of a bedraggled reservoir. The exposed mud-flats looked dingy from afar, but up close we discovered a treasure trove of snail shells, which apparently never get old when you’re seven. (Later, at home, we discovered that each shell was graced with its own fawn-colored patterns, and the array drew our admiration.) 

Still at the lake, pockets full, we turned and walked backward up the hill, hoods turned against the bitter wind. This small adversity just magnified the adventure. Near the top, a great bur oak tree stretched out a hand invitingly. That silent appeal was all it took to get both kids climbing into its rough and sloping lap.

So nature was not entirely absent during my time in the city, but the tidbits I devoured just served to sharpen my hunger. Curtains were drawn all day, and anyway, the windows just looked out on lawns and houses. The cardinal singing above the rush of cars. The fresh flowers wilting in the cavernous wedding reception hall. The cottontails in the backyard racing like maniacs with their friends at dawn, each in their own chain-link box. The great blue heron—dignity intact among the exploding development of suburbia—gliding in to land in the manicured pond on the community college grounds.

And hawks. Mostly red-tails, but probably others, too; hunting from utility poles, from fence posts, and from above rushing traffic. I caught my breath as one dove like a streak of wildness into the dried road ditch grass.

Nature is everywhere, if you allow yourself to see it. I take comfort in that. I know that many have learned to live on these tidbits, with an occasional banquet at a national park. I haven’t, though. I’m always hungry for more, needing daily feasts and occasional full immersion experiences to quench my thirst.

Here at the end of my driveway, I drank my daily fill, and planned for more. As I turned to go, the eastern sky was deepening into a rich blue, but a golden sun played peekaboo to the southwest. Just a few trunks were lucky enough to feel the caress of its last rays. I feel like I’m one of the lucky ones, too. Not everyone gets to live in the Northwoods. But not everyone wants to. Maybe others thirst for the excitement of cities, or the comforts of suburbs. Me, I thirst for the comfort of hemlock boughs and the music of a fox.

Ok, I know this is a white pine, but you get the idea.

“Climb the mountains and get their good tidings. Nature's peace will flow into you as sunshine flows into trees. The winds will blow their own freshness into you, and the storms their energy, while cares will drop off like autumn leaves.”  --John Muir

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at http://cablemuseum.org/natural-connections-book/.

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: "Better Together--Celebrating a Natural Community" will open on May 3!

“To appreciate what is seen”

Freeze. Thaw. Thunderstorm. Snow. Plummeting cold. Gradual easing. This weird weather on the edge of spring has me feeling gloomy. My favorite winter activities demand snow. My favorite summer activities demand warmth, or at least a bare, frozen trail. Even the woods feel emptier, since good tracking snow is hard to find and migrating birds have mostly paused farther south.

Lois Nestel, the Museum’s founding director, also experienced this, and it is through her wisdom that I am reminded to appreciate the pieces of nature that are still out there, if we take the time to see.

“There are times when the winter woods are so still, so empty, that walking in them, one feels like the last living creature,” wrote Lois. “Not a track mars the snow; not a sound stirs the air. Where has everything gone? It is strange because a few days earlier there may have been an abundance of life in many forms.”

“On one of those days I set out with a definite purpose in mind. I was stalking a pileated woodpecker whose calls and rapid fire hammerings seemed to come consistently from one area of trees not far from the house. These big, wary birds are not easy to pursue, so reasonable caution was necessary.”

“Silence ahead seemed to indicate that the big bird had flown, but the apprehension was dispelled as, from a pine stub ahead, there came a staccato burst and bits of flying wood. A stealthy approach, timed with the pecking, ended abruptly when a large black beak topped by bright eyes and a flame red cockade was suddenly thrust around the side of the stub. With much scuffling of feet the crow-sized black body came into view. Unaware of being watched, the big bird seemed to talk to himself with soft knocking notes as if trying to decide where to drill the next hole.”

“Some unwary movement or sound on my part suddenly alerted him. There was a brief eye-to-eye confrontation; then the broad wings spread and with a few swooping beats bore the great woodpecker into the safety and seclusion of the forest.”

“The pine stub bore evidence of much work. Large openings had been chopped through the shell and into the honeycombed interior. Breaking open a piece of this riddled wood revealed the dormant bodies of large black ants. This was what had attracted the woodpecker and would undoubtedly bring him back again. I might not be around to see, but the sound of drumming would bring to mind a clear picture of a great black bird with a flaming topknot—a memory to treasure.”

Pileated woodpeckers are a thrill to see in any season, and while they have become more common, you still can’t expect to see one on every hike. In contrast, there are beautiful, sedentary wonders which can increase enjoyment on any outing.

Lois continued, “Most people are aware of the beauty of summer flowers and often bemoan their passing as winter approaches. This need not be a cause for regret because, while much color may be lost, there continue—as seeds, pods, and capsules—many forms that rival the flowers in beauty and grace. Many of these seed containers last throughout the winter, serving as food for wildlife and pleasure for humans.”

“There is a sculptured beauty in the pods of various milkweeds and wild iris, evening primrose, cockle and Indian pipes. Delicate grace is exemplified in airy sprays of sweet cicely, papery clusters of wild hops and feathery virgin’s bower (wild clematis) twining over bushes, and in the dried grasses and sedges, each with individual form and style.”

“Many fall-blooming flowers (weeds if one must call them that) retain their form if not their color through the winter months. Goldenrod, tansy and yarrow are sepia-toned replicas of summer’s gay colors. Flowers such as asters lift clusters of tan, star-like sepals above the snow.”

“Touches of color do remain in scattered places; the dark velvety red of sumac heads, the red-orange of rose hips and the brighter red of highbush cranberries and hawthorn frozen on their shrubs.”

“To enjoy these and many other beauties of winter there are few requirements; namely these: get outside, have open eyes to see and an open mind, receptive enough to appreciate what is seen.”

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at http://cablemuseum.org/natural-connections-book/.

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is open through March 11.

Awake and Wondering

Fox tracks crisscross my yard. Down the trail to the lake, along the shore, across the hill, and back. The strings of tracks remind me that I’m not the only one who lives here. These woods are alive, even under the blanket of snow and the low-slung stars. I try to read the fox’s nocturnal adventures in the tracks—to guess at his life in the forest—but so much of nature, even when the daylight shines again, retains its mysteries.

Have you ever wondered what happens out there, under the heavens, while you sleep? I went to bed last night with a crystal-clear sky; stars sparkling like diamonds in the plummeting cold. This morning I woke to a blanket of clouds and a dusting of snow on my windshield. When did the clouds roll in? What did the snow look like as it fell? Who was out there to see it? Was the fox trotting along thinking, as poet Mary Oliver infers, “It is music to wander the black back roads outside of town—no one awake or wondering if anything miraculous is ever going to happen, totally dumb to the fact of every moment's miracle…”

The sparkle of hoar frost (from the Norse hārr, “gray with age”) on the trees this morning certainly makes it seem like something extraordinary transpired last night while no one was awake and wondering. Extraordinary, but still explained by chemistry and physics. As the temperature dropped below the dew point, water was squeezed out of the air. In this case, the dew point just happened to be below freezing (therefore it is technically called the frost point), so water precipitated as ice on cold objects instead of condensing as dew. The frost crystals often form intricate patterns that scatter light, making them appear like a white frosting on all the trees, as if the world was made of glitter.

Down the trail to the lake, along the lakeshore, I make my own tracks. Two parallel ribbons stream out behind me as I kick and glide on the frozen lake. Howling winds have sculpted the surface into a miniature, sand-less Sahara. Shallow, snow-dust storms skitter across the surface (the sculptures are works in progress), making me feel like a giant peering down onto the wilds of Antarctica. The abrasion of crystal clouds sounds like radio static. A loud crack and eerie boom echo through the ice. I can feel it reverberate under my skis. This raises my heart rate far more than the swinging of arms and legs.

As the temperature drops again after weeks of unseasonal thaws, the ice expands and fractures. I can see fresh cracks where they sketch rough fault lines through wind-packed snow.

During freeze-up, thin ice acts as a huge membrane across which the crackling and popping sounds spread. One website, devoted to recording these ice songs, (search “Dispersion of Sound Waves in Ice Sheets” to find it) explains that: “The high frequencies of the popping and cracking noises are transmitted faster by the ice than the deeper frequencies, which reach the listener with a time lag as glissandi (a glide from one pitch to another)” Science explains even the marvel of ice singing.

This late-winter ice is merely expanding back toward the shores it had shrunken away from when they reflected too much of the sun’s warmth. It may also be adding depth to an already substantial thickness. The deep pops and rumbles sound like winter thunder.

Almost home, a black shape lopes out of the white pines on the point. I pause to squint, then ski faster, hoping that it will come into focus. The apparition catches sight of me and reverses course, turning back into the trees. I spend the next few minutes in suspense. Who will the tracks reveal? Otter? Fisher? Fox. Its small, four-toed tracks and two-by-two side trot pattern are unmistakable. This red fox was looking at me as it ran, causing its front feet both to land on the left side of its trail, and its hind feet to land on the right. I look from the tracks into the woods, my questions only half-formed in the half-light.

Diagram of a fox side-trot from James Halfpenny's A Field Guide to Mammal Tracking in North America.

As day fades back to twilight, I sense again the music of wandering the back ways outside of town. A fingernail moon glitters, ice thunders, a fox hunts in the snow, our planet spins toward spring.

Tonight I, and maybe you, and maybe even the fox, are awake and wondering.

What is this moment’s miracle?

Note: Portions of this article were published in 2013.

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at http://cablemuseum.org/natural-connections-book/.

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is open through March 11.

Goldenrod Gall Moth

This morning I took my camera out looking for an adventure. The otters’ early morning tracks went run-run-sliiiiiide along the lakeshore. A pair of fox tracks trotted merrily down the driveway on a date (complete with double scent marks!). Shards of snow clung to emerald moss as it clambered a maple’s craggy bark. The morning was beautiful, but still nothing inspired me. So I buckled down at my computer to fill in spreadsheets and make graphs.

The data I organized are actually pretty interesting. In December, sixth graders at Drummond dissected goldenrod galls and recorded their contents and diameter. Most of the time they found the plump goldenrod gall fly larva who created the gall. Occasionally they found a wasp or beetle larva that parasitized the gall larvae. I love telling the story (you can read about it in my book), and they love discovering it.

Suddenly, in the middle of copying my final graph into the slideshow for class, I got up with a half-formed thought and wandered into the kitchen. Digging to the back of the freezer I pulled out a folded zip-top bag with a dozen or so brown galls. Here were the leftovers from that December class. These weren’t smooth and round like most of the galls we dissected, though. They were oblong, spindle-shaped, with some smooth ridges like musclewood bark.

Unthinking, I’d handed one out in class with the rest of the galls, and a girl opened it up. Inside the oddly spacious cavity was a large, crispy, dark-brown larva. This wasn’t the same insect we’d been studying! I’d always meant to research these elliptical galls, but hadn’t gotten around to it. So I packed the gall and the larva into a petri dish and stuck the rest of the odd galls back into the freezer. Until today.

Excited now, I took out my trusty dissecting tools: a paper plate and serrated butter knife. One by one I opened the elliptical galls. Empty. Empty. Empty. They were all empty, with large cavities. A white film coated the inner chamber. Did a fungus kill them? Poking deeper, I noticed a small hole near the top of one gall. An exit tunnel!

Finally, the last and largest gall revealed another crispy larva. Under the dissecting scope, I noticed many small holes in the dried exoskeleton. Weird. Now I was hungry for information. Using Google images, I quickly matched the image of the gall to a name: goldenrod gall moth—Gnorimoschema gallaesolidaginis. This frumpy moth has a one centimeter long body and two centimeter wingspan. The forewings are dark, and the hind wings are pale and fringed. It’s not much to look at, but drama unfolds when you did deeper. In 1963, William E. Miller of Ohio State University wrote a classic natural history article titled: “The Goldenrod Gall Moth Gnorimoschema gallaesolidaginis (Riley) and its parasites in Ohio.” I’ve summarized his information below.

Gnorimoschema gallaesolidaginis by Simon Carmichael

The goldenrod gall fly larva that we usually study spends its winter frozen inside the gall. 

Goldenrod gall fly larva

This gall moth takes a different approach, and it explains why I found no live larvae in the galls. The adult moth lays its eggs on the dying lower leaves of goldenrod plants in late summer and fall. The eggs overwinter there. The adult dies. Once a larva hatches in spring, it must seek out a newly sprouted goldenrod nearby. The larva eats its way in through the terminal bud and into the pith of the stem. Just a few inches below the terminus, it sets up shop. Growth hormone-like chemicals in its saliva trigger the plant to grow the elliptical gall.

After feeding inside the gall all summer, the larva chews itself an exit hole, leaving just the thin outer skin of the plant intact. Then the larva fashions itself a plug for the hole out of sawdust and silk. Brilliantly, the exit hole is wider on the outside and tapers toward the inside. The plug fits just like your bathtub’s stopper, and is easy for the moth to eventually pop out, but hard for an invader to push in.

Next, the larva lines it cavity with silk. In doing so, it both seals the chamber and creates a sort of guide to help the adult moth find its way out. The white film I attributed to killer fungi may actually have been helpful silk! Once both the escape hatch and runway are in place, (sometime in July or August) the larva pupates. The cocoon stage lasts four to six weeks, and then the moth emerges in early fall, pushes open the plug, finds a mate, and continues the cycle.

This ideal scenario rarely happens. About half of the larvae succumb to parasites, mostly parasitic wasps. While reading Miller’s graphic description of the various parasites, the meaning of the dried larval skeleton riddles with holes became clear. “Copidosoma g gelechias is a polyembryonic internal parasite of the larva,” wrote Miller. What does that mean? This tiny wasp lays a single egg inside the moth egg. The moth larva hatches in spring, and it grows normally until the wasp egg clones itself and produces lots of wasp eggs. The wasp eggs hatch and are “set free in the host’s body cavity.” The parasites eat the moth larva from the inside out, leaving only the chitinous hard parts, and conveniently waiting to finish it off until after the moth larva excavates the exit hole. Some wasp larvae grow bigger than others, and they attack the larvae of any other wasp that might also have parasitized the moth. In the end, the wasps pupate and emerge, leaving behind a hollow shell riddled with holes—a hollow shell which now sits on my desk.

Driving home past ditches full of dried goldenrod stems, I couldn’t stop thinking about this amazing story. How many more stories are hiding there, just in that ditch?

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at http://cablemuseum.org/natural-connections-book/.

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is open through March 11.