My husband and I traveled to the Lower Peninsula for a long weekend to visit family. We had some nervousness about making a quick trip in winter weather, so we decided to play it by ear and only leave if the weather forecast looked reasonably good.

We arrived to warm (comparatively) weather, with temperatures as high as 40°F. We haven’t seen temperatures above freezing since the fall, so this felt incredibly warm and luxurious. The foot-or-so of snow on the ground seemed paltry compared to the feet of snow we have in the woods back home. The sight of open water in rivers, bare ground near Lake Michigan, and a robin made it seem like winter would be lessening before too long.

I went for a ski at the Big M Trails one morning. It was about 30°F (so warm!) with a slight breeze that was barely perceptible in the woods. I decided on a slow ski, which was good because the more heavily used trails were icy enough that it was sometimes hard to get traction.

There were snow fleas everywhere. I knew that snow fleas existed, but I don’t think I’d ever really noticed them before.

Snow fleas look like black pepper on snow until you look close up. Photo via Wisconsin DNR.

So I wondered: What are snow fleas? A few things I learned while searching around the internets:

  1. Snow fleas aren’t fleas. They aren’t even technically bugs. They are a type of arthropod (the phylum of organisms that includes insects, spiders, and crustaceans) called a springtail. Since they aren’t fleas and don’t have biting mouthparts, they are completely harmless.
  2. Snow fleas can jump. The snow fleas look like black pepper flakes scattered across the snow, but you can see them hopping around if you take the time to look. Springtails jump using a tail-like structure called a furcula, rather than with their legs.
  3. The outdoors is full of snow fleas, all year long. Springtails are extremely common in damp soils and under leaf litter, where they feed on fungi, algae, and decaying organic matter. There can be millions of springtails in a small area and you’d never notice them because they are to tiny and hard to see against a dark surface.
  4. Special antifreeze lets snow fleas be active in winter. One or a few species of springtails in the genus Hypogastrura have an adaptation that lets them be active in winter. The amino acid glycine helps prevent the formation of ice crystals in cold temperatures, allowing the organisms to be outside in conditions that would typically be fatal.
  5. Snow fleas emerge in warm winter weather, although people aren’t entirely sure why. Warmer winter conditions allow snow fleas to emerge from the soil, often near tree trunks or other vertical structures. It’s a little unclear why the snow fleas emerge, but it could be caused by overcrowding underneath the snow or a chance to eat fungal spores and algae on the surface of the snow.
Super close up! Image via David Reed at www.bugguide.net

It turned out that the warm conditions were only temporary, and a severe blizzard struck much of northern Michigan and the Upper Peninsula during our trip. Plows were pulled from the roads, and many major highways were closed.

Road closures across Michigan, 25 February 2019.

We still have a lot of winter left. We don’t even plan to tap our maple trees for another month. But when the weather in the Upper Peninsula does start to warm, I’ll be on the lookout to see if we have snow fleas in our woods.

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