Prairie Ridge Ecostation

Winter in Water

As the weather starts to cool, we will start to see fewer and fewer insects active at Prairie Ridge.  Because they are endothermic (“cold blooded”), many insects enter a dormant period during the cold months, often overwintering in some hidden, protected spot as eggs or larvae in a sort of suspended animation until spring or summer.  However, there are places on the Prairie Ridge grounds where you can find insects active year-round, where even on the coldest winter day you might still find insects going about their regular business: our stream and pond.

In spite of some of the difficulties that life in water brings for aquatic insects, it’s still a great place to live.  Most importantly, water is very thermally stable.  It takes a long time for water to heat up and cool down, especially in large quantities.  This means that aquatic insects often experience far less fluctuation in temperatures than their land dwelling relatives.  Many aquatic insects are also well adapted to living in a cool environment and are quite capable of carrying on with their regular lives in our relatively mild winters.  Short of freezing over (and maybe even then!), you will be able to find at least a few insects swimming around in our ponds and stream even on the coldest days of the year.

A trip to the pond and a few sweeps of a net will currently yield a surprising diversity of aquatic insects.  Dragonfly nymphs are quite common:

dragonfly nymph

Many dragonflies overwinter as immatures (nymphs) in the water, so even though you might not see adult dragonflies flying, you can still find lots of nymphs that will emerge as adults next spring or summer.  Dragonfly nymphs are wonderful creatures, expert hunters with an amazing extensible mouthpart that they use to reach out, grab, and hold prey while they eat.  These highly visual predators are an important part of the pond’s ecosystem.

Another fascinating aquatic insect from the pond is the phantom midge larva:

phantom midge larva

These will eventually pupate and emerge as flies, but they are spectacular as larvae!  Phantom midges are almost completely transparent, a trait that protects them from predators such as fish (though we don’t have fish in the Prairie Ridge pond) and dragonflies and allows them to swim brazenly right out in the open water.  When you scoop these up in the net, you can barely see them unless they move, and then only because they carry two internal air bubbles that reflect light.  You are unlikely to see a phantom midge larva simply by looking into the water, but there are thousands of them (maybe millions) swimming about in the water in our pond!

A great predator is the creeping water bug:

creeping water bug

They’re a lot smaller than some of the other predatory insects in our pond, but don’t let their smaller size fool you.  These insects are fierce!  They have a powerful paralyzing venom that they inject into prey after capture, so these insects can capture and eat things that might seem too big for them to manage.  The bite can also be painful to people who come into contact with an unsuspecting creeping water bug.  They’re not inclined to bite in general, but will bite to defend themselves from perceived threats, so handle these insects with care.

These are just a few of the insects active in the water now!  You might also find midge larvae, giant water bugs, water scorpions, predaceous diving beetles, water scavenger beetles, mayflies, caddisflies, or other aquatic insects happily swimming about in the water or nestled safely under rocks, not to mention an array of tadpoles, salamanders, snails, worms, and crayfish.  It might seem pretty dead on land in the winter, but the aquatic habitats are still going strong and are teeming with life!

Take a look in the pond or flip a few rocks in the stream the next time you visit Prairie Ridge.  You might be surprised by what you find!

Find out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive!

Image by Chris Goforth.