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Snow fleas aren’t really fleas

Hypogastrura nivicola
Credit: iNaturalist
Hypogastrura nivicola
Snow fleas aren’t really fleas

Snow fleas are neither fleas nor insects. In fact they’re springtails, little arthropods that are close cousins of insects, and they belong to the species Hypogastrura nivicola.

The springtail is dark blue and measures 1 to 2 millimeters in length. It has no wings, and walks with the help of claws located at the end of its six feet. When it needs to move around more quickly, it uses its furca, a fork-shaped appendix located under its abdomen. The furca enables it to propel itself into the air and to leap long distances. That’s how it escapes from predators and from curious humans who get too close.

Where do these little arthropods come from?

Springtails live in soils that are rich in organic matter as well as along bodies of water. In the spring, when the temperature is around 0°C, they climb up through the layers of snow, often at the foot of trees or close to big rocks. Several hundred individuals can be found in the same spot and make up little clusters, similar to black dust, deposited on the snow. When the temperature drops, they go back to where they came from.

Why and how are they active on the snow?

If springtails come up to the surface, it’s to feed on the algae, microorganisms and fungus spores that they find on the snow. Since the start of winter their metabolisms have been at rest: they breathe less, no longer eat, don’t grow, and have stopped breeding. They survive in cold temperatures notably thanks to “antifreeze” proteins present in their blood. But what has also been determined in this species is that those proteins additionally allow them to ingest food when temperatures grow milder. How? By keeping the little ice crystals swallowed at the same time as the food from growing inside their tissues when temperatures drop once again. The presence of those proteins in their organisms therefore prevents the little animals from bursting if they ingest too much ice.

What are these springtails good for?

However tiny they may be, springtails are highly useful. Because of their abundance in the soil (the density can reach 100,000 individuals per square meter), their feeding activities help decompose organic matter, return nutrients to the soil and make them available to plants. These springtails also serve as food for numerous little animals and exercise a degree of control over the fungus, bacteria and nematode populations present in the environment.

So if at some point during a springtime stroll with friends you notice some snow fleas, reassure them (the friends) by pointing out that, unlike fleas, these minuscule beasts don’t bite, and they won’t infest you!

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