Winter Insects are Cool

Features - Seasonal Pests

Now that temperatures have dropped, you may start getting calls for some unusual winter pests. Here’s what you need to know.

November 5, 2020

Snow fleas appear in huge numbers in early spring. They are about 3/64 inch (1.2 mm) long and are dark blue-gray in color. The furcula on this species is very long and allows them to jump on the surface of the water.
Kansas Department of Agriculture,

By Chelle Hartzer, B.C.E.

Those in the northern part of the country know that winter usually brings a reduction in insects. When freezing temperatures, snow and ice blanket the outside, most of our pests tend to hunker down. They wait for warmer temperatures before coming out to bug us again. Sure, there are indoor overwintering pests like lady beetles, stink bugs, cluster flies and more. But there also are insects that are actually active in winter that can result in calls from confused customers.

SNOW FLEAS. Every winter, there are calls for “snow fleas.” They tend to be small, bluish grey to almost black, and appear to jump all over the white snow. The contrast of their dark bodies against the light snow makes them stand out and customers will notice them quickly. These are springtails (Collembola) which are tiny, soil-dwelling insects. No one knows exactly how many species there are because not much research has been done, but it is estimated that there are around 700 species in North America. Most will remain in the soil all winter but a few species seem to relish the cold and emerge on somewhat warmer days. Because they come on in such high numbers, they can accidentally get into structures, especially garages and basements. They are harmless and won’t survive long indoors because of the warm, dry conditions, but a residual crack and crevice treatment around openings can help keep them out. For those on the outside, let customers know what they are, that they are harmless, and that they should double check all their ground-level door seals.

Midges are often found around freshwater areas.
David Cappaert,

MIDGES. There are also several flies, mostly midges, that are active during winter. Like springtails, these insects can emerge in huge numbers that can concern customers. Midges are aquatic in their immature stages so adults are often found near streams, ponds and other freshwater areas. Like mayflies in the spring, there will be massive swarms of these insects as they emerge as adults and quickly look for a mate. The bad news is that they can obviously enter structures through doors, windows, vents and other openings — especially if they are near a freshwater source. The good news is these immense clouds of midges don’t last long. Adults only live a few days. Adult midges also are harmless; they don’t bite or sting, nor do they carry any diseases.

Kansas Department of Agriculture ,

SCORPIONFLY. A personal favorite of mine is the snow scorpionfly. If you have never seen a scorpionfly then imagine a fly, with a scorpion-like tail, four long thin wings like a termite, eyes that take up most of their head, and long thin mouthparts that look like an elephant trunk. As scary as that may sound, they are harmless. This particular family of scorpionflies is wingless and the “tail” is reduced but still visible. Both the adults and the larvae feed on moss and decaying plant material. Adults can be seen from October through March depending on temperatures and weather conditions. Because they crawl and jump, there is always the chance of them getting into homes and businesses. However, customers are more likely to find them on the outside against the white backdrop of snow.

STONEFLIES. Stoneflies also are active in the cold winter months. Two families in particular are called winter stoneflies and the adults can be seen walking near streams and freshwater, even sunning themselves in bright areas. The larvae are aquatic and live in fast-moving, coldwater streams and rivers. Larvae feed on plant material and adults feed on algae so these are no threat to people. Because of their long wings, customers can sometimes mistake these for winged termites or ants. Looking closely, you can see the long antennae and that the body shape isn’t quite right for termites or ants. These don’t emerge in enormous swarms so it’s likely there will only be a few found at any one time.

SNOW FLIES. Lastly, there are snow flies. These are a type of crane fly and look like a cross between an earwig, a spider and a midge. They have the fairly typical fly head with the shorter antennae, long and spindly legs that splay outwards like a spider, and the “pinchers” at the back like an earwig. They are also wingless, which makes them look a bit like a spider. Larvae are typically found in wet leaf litter and adults will emerge on sunny days. When customers see snow flies, which can run fairly fast, they often mistake them for spiders.

FINAL THOUGHTS. Even in the cold winter months, there are active insects. Some customers may notice mass emergences or small clusters and the occasional one or two may get into structures. Properly identifying the insect can tell the customer (and you!) what they are and what to do about them. If you haven’t encountered any of these, or are living in the southern part of the United States, that’s OK: Bed bugs and head lice are active all year round!

The author has been working in the pest management industry for more than 10 years and is a Board Certified Entomologist. Email her at