At the beginning of my Wolf Ridge adventure, back in October, I was walking up the trail from Wolf Lake when I spotted something strange. A wispy, fuzzy, white substance coated the branch of an alder tree. Was it a mold? A fungus? I had no idea. Upon questioning my professor and doing some research, I learned that it was a woolly alder aphid, Prociphilus tessallatus. Though the creature itself is interesting, the world of the woolly alder aphid, filled with farming, deception, and carnivorous caterpillars, is truly amazing.
Woolly alder aphids begin their lives on maple trees, where the young hatch from eggs and feed on maple sap. In the summer the aphids, now with wings, move to alder trees. This entire generation is female, and will produce live young, all wingless females, parthenogenetically (without a male). The aphids eat sap from the alder and apparently cause it no harm. Ants will milk the aphids to receive honeydew, a sweet substance the aphids secrete. In return, the ants protect the aphids from predators, such as green lacewing larvae and the harvester butterfly caterpillar, the only known carnivorous butterfly species in North America. To sneak past the feisty ant farmers, harvester caterpillars pluck wool from the aphids to hide themselves. They have been known to cover themselves in aphid carcasses in order to roam among the aphid flock, a “wolf in sheep’s clothing”, so to speak. The caterpillars also have a chemical camouflage that mimics the chemical makeup of the aphids, further deceiving the perceptive ants. Luckily for the aphids, enough of them survive for the latest generation of adults, now male and female (and again sporting wings) to fly back to maple trees in the fall. The females then lay their eggs to begin the cycle once more.
Even though I spend a lot of time outdoors, this fascinating tale was unknown to me until this year. It makes me wonder what surprises I’ll discover next! The next time you take a walk through the woods, look closely at an alder tree to see if you can find the woolly alder aphid. And while you’re out there, try to uncover a story that surprises you!