Katherine Woolley is about to start her junior year as an environmental education major at Western Colorado University. This summer, as a Summer Naturalist Intern at the Museum, she taught our Junior Naturalist programs and showed a real talent for finding and appreciating the oddest parts of nature.
A walk along the Forest Lodge Nature Trail is never boring. I was reveling in this fact as I took my evening meander through the large trunks of towering trees. To my left, I spotted a shelf fungus clinging to the bark of a half-decayed paper birch stump. Creeping closer to investigate, I peered up, to the side, then the other side. Then I crouched down and took a good look at the underside of the fungus, my eyes squinting in the bright evening light. I squealed with delight. There they were! Two forked fungus beetles were nestled in the corner of their polypore home.
Despite being one of my favorite insects, this was only the second time I had ever been gifted with their presence. My first encounter with forked fungus beetles was almost two years ago but only a few miles away on a Northland College field trip to the Forest Lodge Estate on the south shore of Lake Namakagon. While there, a fellow classmate and I roamed the grounds together. We first spotted a shelf mushroom, and then when investigating further, spotted a weird brown bump. Looking closer, the bump had legs, antennae, was moving, and was not actually a bump at all, but an insect.
With a gasp of awe, I called my other classmates and professor over to see this amazing creature, but not a single one of us had ever seen one before. Later I found out through the iNaturalist app that this insect was a forked fungus beetle. These beetles only live east of the Mississippi River. Until my move to Wisconsin from where I had grown up in Minnesota, I had lived west of their range. After that encounter, my friend and I spent the following summer scouring the forests to find another beetle, but to no avail. That made it even more thrilling to spot these two beetles this summer.
The particular mushroom where I spotted the beetles that day was filled top to bottom with a wide and intricate network of holes. While searching for beetles, I discovered that holes like the ones I saw are a great indicator that fungus beetles are present. This is because their larvae are the ones who create these holes by burrowing inside the woody polypore after they hatch from eggs that are laid on the outside of the mushroom.
Once inside the polypore, the beetle larvae go through their final two stages of metamorphosis—pupae and then fully formed beetles—rather peacefully by giving each other a wide birth. Even so, if a larva happens to stumble across a pupa who is still forming into a beetle inside the mushroom, they may eat that pupa! Pupae who survive the hungry mouths of their brothers and sisters emerge from their pupal cases a pale whitish yellow. After emergence, the beetles stay in their cases for a few days until they develop their characteristic deep woody brown and wet-bark-black colors.
Forked fungus beetles can spend the winter in either the adult or larval stage. Adults hide safely tucked into fungus, stumps, logs, and other decaying wood to wait for warmer weather. The larvae stay snug inside the polypore tunnels and then start their transformation in spring. Generations of the same beetle family will live on the same mushroom for up to nine years, moving onto a different polypore when the clutter of holes becomes unlivable.
After I snapped some pictures, I wondered if I kept coming back to this stump if I would see them again. When forked fungus beetles are born, they don't often go far. These beetles can fly, but they very rarely do. I took a final look at the shelf mushroom, looking for eggs. Finding none, I bid my beetle friends farewell. As I traveled farther down the trail, I stopped at every shelf mushroom with hopes to discover more fungus beetle strongholds, but there were none. I suppose their elusiveness is part of what makes seeing them such a treat. I smiled in gratitude at their stump on my way home.
For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our Summer Calendar is open for registration! Visit our new exhibit, “Becoming the Northwoods: Akiing (A Special Place). Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.
Last Update: Aug 06, 2025 10:22 am CDT
