Snow fleas are harmless and abundant

Knowing that winter weather can persist into April, there will probably be at least a few more opportunities to see a tiny, but abundant creature that is best seen against a blanket of fresh snow — snow fleas.

Last week a friend told me that after a recent snowfall he was walking along his sidewalk when he noticed some dark “stuff” on the snow.

He said; “It looked like soot, but there’s no source near my house. When I looked closer, I realized the individual specks were moving, even jumping. When I got to my computer I googled, ‘tiny insects jumping on snow.’ I quickly learned that I was seeing ‘snow fleas.’ Can you tell me more?”

Lots of concern

Curiously, the very next day I received two emails asking about the very same phenomenon. First, snow fleas are not fleas. They are springtails, tiny ever-present insects that are rarely noticed. Against a snowy white background, they become much more conspicuous. And though they are abundant, springtails are harmless to humans.

Even if you find some in the house, ignore them or suck them up with a vacuum. Springtails are classified as members of the insect Order Collembola. They lack wings, and most are just one to three millimeters long. It takes a hand lens to get a good look at them. The trait that gives springtails their name is a long, forked, tail-like structure called the furcula, that folds under the abdomen.

When startled or threatened, springtails release the furcula and it catapults them forward several inches. If humans could jump a comparable distance, the Olympic long jump record would probably be in triple digits.

When just going about their business in the leaf litter, springtails walk on their six legs. Another interesting anatomical feature of springtails is their inverted mouthparts that one entomologist describes as looking like they “have lost their dentures and then sucked on a bunch of lemons.”

Springtails make up for what they lack in size with sheer abundance, and that’s why we occasionally notice them. Dense swarms are common, but we usually only see them when they appear against a contrasting background such as snow.

On sunny winter days, they can blacken entire patches of pristine snow. These aggregations, which can number thousands of individuals, may relate to breeding behavior, feeding, or a chance to traverse predator-free surfaces.

Though it’s sometimes difficult to appreciate the role that such tiny creatures play in nature, they are scavengers and recyclers. They eat fungi, algae, mold, bacteria and decaying organic matter.

In turn, springtails are an important food source for many small invertebrate predators. And if you have ever seen small birds seeming to eat snow, they may have been dining on springtails. Though springtails avoid predators with sudden leaps, some species exude toxic blood from tiny pores on their body. Others are covered with slippery scales that make them difficult to catch.

And some, such as snow fleas, venture onto the snow to avoid predators. Snow fleas employ two adaptations that enable them to tolerate a cold snowy environment. Their dark bodies absorb solar radiation. More important, however, are fluids in the blood that act as anti-freeze.

Glycerol prevents snow fleas and other winter-active insects from freezing solid. It’s the same principle that allows wood frogs, which are now becoming active after months of hibernation, to freeze solid in forest leaf litter.

Though seemingly unimportant due to their small size, springtails are a critically important component of healthy soil. A square yard of forest leaf liter can shelter tens of thousands of springtails and their nutrient-rich feces.

Under ideal conditions, springtail populations can reach 1.4 billion per acre. They recycle nutrients by grazing on fungal hyphae (roots). The symbiotic relationship between springtails and fungi enhances plant growth at all levels.

When you till the garden this spring, watch for high hopping springtails. They indicate that your soil is healthy and ready to grow a bountiful crop of vegetables.