Marcia Roepke
Trail Time

Trail Time – Fall on the Gunflint Trail

What a beautiful time to be on the Gunflint Trail! The woods are rich with summer’s growth letting loose and letting go — yellow leaves from birch and aspen drift down and line the forest floor with gold hues. Pincherry, bush honeysuckle and mountain ash leaves exhibit myriad colors all on one plant — from maroon to lime green to a warm gold in a gorgeous mix of rich autumn tones. Moss, plump from recent rainfall and glowing emerald in the low-angled sunlight, forms soft inviting mounds over rock and earth. After a dark and drizzly morning today, the sun is shining, and the maple trees are blazing in the warm sun — their colors blare out like visual trumpet sounds surrounded by the cooler saner tones of pine, balsam and spruce. The wind is fickle today, blowing in gusts, tugging leaves off the bushes and trees and making them whirl and dance in the air. Then the wind stills, and gold falls to earth. We are blessed by the richness of nature.

 The glory of autumn colors tells us the trees are preparing for cold. Its the time of year when deciduous trees withdraw their contact with the leaves; a barrier layer of cells forms at the stem/tree connection. The absence of chlorophyll lets all the other colors shine in each leaf. The trapped sugar in a leaf produces compounds (different amounts for different species) that combine to form the warm tones of autumn. The leaves are now free to fall and to fly. The same is true for the tamarack needles.

 The slender, silicone-like needles of the tamarack have already started turning yellow and some trees have already lost most of their needles, depending on exposure to wind and rain. Unlike the needles of the evergreen conifers, the deciduous tamarack’s aren’t hardy. They are widely spaced so they can capture more energy in the summer and their absence in winter means the tree will suffer less damage by heavy wet snowfalls.

 Leaves and needles aren’t the only thing turning orange and yellow in the fall. I came across an unfamiliar caterpillar a few days ago while hiking a forest path. It was plump and about three inches long; soft orange with a stripe of blue sandwiched between black running down its back. A row of black spots, each above a leg, dotted both sides. In the front, its comically round head had two black spots, like little cartoon eyes. I tried to identify the cute many-legged creature using moth and butterfly books in my nature library — no success. I resorted to a google image search. Surprise! It wasn’t a caterpillar at all but a sawfly larva, Cimbex Luteus, maybe. The clue to identification lay in the number of legs. A caterpillar has 2-5 pairs of prolegs on the abdomen, while a sawfly larva has 6 or more. My little specimen had eight. As sawfly larvae mature, they turn yellow. The orange one I spotted was quite young; maybe it emerged that day. They feed on alder and willows. The adult sawflies are easily confused with wasps, especially the males, which are yellower than the reddish females. Their antennae are clubbed at the end. Most sawflies eat only one species or closely related species.

 The willow is one of the unsung heroes of our forest and a particular favorite of mine. In Minnesota there are over 20 species of willow. Willow is a keystone species for supporting caterpillars, which feed many animals and birds. Best-selling entomologist Doug Tallamy said in a recent interview on Northern Gardener that willows support 359 species of caterpillars.

 I learned that creepy crawlers like larvae and caterpillars are more efficient than any other animal at converting plant energy to food. When they are eating, they are changing plant amino acids to proteins. Larvae and caterpillars are crucial food sources for birds and other animals like turtles, foxes, voles, mice and even bears. A researcher found that one female bear ate 16,000 to 22,000 tent caterpillars per day, or 20-22 pounds! The hard casing of the tent caterpillar is indigestible in a bear’s stomach, so it was easy to count the spoils after the bear was done with them. I think you get the picture as to what the researcher’s work entailed. It might have been easy to do, and as much as I love nature, I don’t want that job. But I’m so glad someone was willing to do it, if only to make clear how important caterpillars and larvae are to the very foundations of the forest we call home.

 — Marcia Roepke