Giant leopard moth caterpillar

Giant leopard moth caterpillar

Transitions. Autumn began just a few weeks ago but the lush green of this early October tells a different story. Signs of change were our main theme today as twenty-one of us went out in search of red, yellow, and orange. What would birds and mammals be worrying about with the slightest hint of cooler weather appearing? How would trees be responding after getting soaked with 8.5 inches of rain in September? What interesting fungi might be encounter thanks to all that rain? We crossed under the gate to Longenecker Horticultural Gardens to find out.

Fall was not immediately visible. Green grass and green leaves filled our eyes as we passed the lilacs and magnolias and crabapples. The large Norway maple in the birches section had only green leaves. We made our way to the maple section and there found our first clear sign of the season. The bonfire sugar maple was aglow on one side with fiery red leaves. The sugars in maples—especially red and sugar maples—give us some of the best fall colors. These compounds become visible as chlorophyll, which reflects green light and therefore appears green. As chlorophyll production slows and then stops in the fall, the remaining compounds, such as carotenoids and flavonoids, reflect a variety of yellow, orange, and red light into our eyes. Goldfinches with muted plumage chirped overhead on their way to food. A small flock of turkeys ambled its way west, grabbing worms out of the grass. We stopped to examine some empty horse-chestnut capsules, touching their spiky exteriors. The faint yellows of locust, aspen, and finally birch leaves gave us something to ponder as we arrived at the trail into Gallistel Woods.

Gallistel was lively with human visitors this afternoon, and the occasional squirrel made busy movements in the dense understory. Now we started to look for interesting fungi on the sides of the trails and noticed several of the familiar cap mushroom types. With so, so many species (possibly 5 million!) and so few common names, fungi are especially difficult to field identify. Fungi fruit in a fascinating variety of forms, including caps with gills and caps with pores, large shelves or a group of tiny shelves attached to tree trunks, clusters of caps, cups or clubs, jellies, puffballs, stars with caps, “birds-nests,” corals, and, slime molds. We spotted a bear’s-head tooth fungus (Hericium americanum) on the end of a down tree trunk and immediately agreed that it reminded us of the large ice formations of the Cornucopia, Wisconsin, ice caves on Lake Superior. Only this fungus’s white hanging spines were a few centimeters long and maybe 16 inches by 12 inches in total. If bear’s-head tooth was indeed what we saw, Mollen and Weber’s Fascinating Fungi of the North Woods suggest it is one of the “most delectable wild edibles of the North Woods, reminiscent of fish.”

We left the maples of Gallistel behind us and crossed Arboretum Dr., starting the last leg of journey through Wingra Woods. I pointed out hemlock and yellow birch, describing the experiment to restore a northern hemlock forest system in this section of the Arboretum. Without the abundant snow cover that blankets the northern part of the state for 4 months (for example, Minocqua sees an average of 105 inches of snow, while here in Madison we only see 50 inches), the understory plants associated with a hemlock forest do not succeed. The hemlock trees themselves in this section of the Arb are small and spindly. A short stop at Big Spring gave us a chance to connect with water and talk about humans living on and around Lake Wingra for thousands of years. We also noticed the unusual sight of conifer needles turning yellow and talked about tamaracks—our only “deciduous evergreen” in Wisconsin. Another few weeks and the tamaracks will be peak gold.

We kept up our pace and watched a skein of seven geese moving in a straight line south over Lake Wingra. Here the season came alive. Another group of turkeys foraged to our left and the woods felt more open and active than they had in September. The last section of Wingra Woods turned up a small treasure for us to see. I picked up a black fuzzy caterpillar with dark orange stripes and walked around for the group to examine. This one was already dead but I later identified it as a giant leopard moth (Hypercompe scribonia), aka “giant wooly bear.” We mostly wondered how these creatures survive the winter to reproduce. My real-time theory about overwintering as eggs was incorrect. The partly grown caterpillars spend the winter hibernating out of the cold. They can survive temperatures down to 14 degrees F. They allow about 50 percent of their body to freeze and use heightened levels of glycerol, which acts to keep water liquid at lower than freezing temperatures by disrupting the water-water hydrogen bonds. Maybe the caterpillar we looked at was actually alive but practicing for the winter?

We ended our tour back at the gate of Longenecker Horticultural Gardens and made one last observation about the changing season. Curtis Prairie lay before us a painting of muted browns, with a swipe of reddening sumac and accents of fading goldenrod. The transition from prairie to forest has certainly begun and the show of fall colors will intensify each day over the next few weeks. I suggested that everyone come back to see the colors each week and watch nature’s show unfold.

—Tom Pearce