Native Animal Profile: Cold Weather-Loving Bugs
Photo by John Mullican
“Paying attention is a form of reciprocity with the living world, receiving the gifts with open eyes and open hearts.” – Robin Wall Kimmerer
A walk outside in the winter months always feels strikingly different from the summer, not just in the temperatures and the way the natural world looks, but in the way it sounds too. Other than the swish of your winter coat, the occasional bird chirp, and the crunch of dry leaves or freshly fallen snow, winter in Maryland can be a pretty quiet environment.
This silence is owed at least in part to the absence of active insects. The buzzing of busy bees and hungry mosquitoes, chirping crickets and shouting cicadas can really cause quite a ruckus, but most of our summer singers seem to disappear in winter.
Some familiar invertebrates take advantage of our climate-controlled houses, living with us year-round, like spiders, roaches, cave crickets, and house centipedes. Others – like the ladybugs and stink bugs that find refuge in our window casings and siding – prefer to cozy up just when they need us. Some bugs migrate, some hibernate, and a large number pass the cold season in an egg, larvae, or another immature form. A large number of Maryland’s well-documented aquatic macroinvertebrates (animals with no backbone that you can see without a microscope) spend their winters in streams as larvae or nymphs. Many use unique adaptations like the production of a chemical similar to antifreeze in their bodies to survive winter conditions and happily live their lives in frigid waters. These winter swimmers are sampled and used by Department of Natural Resources scientists to assess the health of our waterways. One final category is one of the most specialized and interesting: those that somehow remain active in their adult forms, our cold weather-loving bugs.
Investigating Stream Health – MBSS
If you live near a freshwater stream, you are likely no stranger to the existence of very special kinds of insects called the winter stoneflies, sometimes named snowflies (order Plecoptera, families Capniidae and Taeniopterygidae). Named for their tenacious clinging on to rocks in fast moving streams, these flattened, leggy insects spend their egg and nymph stages in water, using feathery gills to breathe and producing an antifreeze chemical to stay thawed. They then go through a series of molts until they emerge from the water as adults, leaving behind their crunchy shed skin (called exuviae), often attached to the sides of bridge structures or rocks along the stream’s edge. Winter stoneflies uniquely time this emergence with the cold, giving themselves the advantage of less competition and fewer chances of being eaten by predators in the months when most other creatures are groggy. They are also fairly weak flyers; this means they spend more time running on land, making it much easier for our human eyes to spot, especially in contrast to snow. They spend just enough time in their adult form to find mates, lay eggs, and start the cycle over again. Not to be confused with midges, a teeny-tiny, gnat-like member of the true fly (Diptera) order that sometimes hatches on warm winter days, stoneflies are regarded as a very welcome mid-winter snack by our local freshwater fish.
Insects like snowflies aren’t the only ones taking advantage of winter’s peace. They have good company in a very little known and fascinating group of invertebrates named snow fleas, part of the group of invertebrates called springtails or Collembola. Collembola don’t technically qualify as true insects, nor are they fleas – but they do have six legs and a tail-like structure that enables them to launch themselves vast distances. They are rarely noticed, but extremely common and live basically everywhere, including highly urban environments like Baltimore City. Most of them hang out in soil, leaf litter, and moist vegetation; they play a vital role in breaking down organic matter, munching on dead things as busy decomposers. Some species are adapted to aquatic life, frequently found near tidal areas and shorelines. Being so tiny and covered in a hydrophobic (water-repelling) outer layer, even land-dwelling species can be found in water, floating on the surface film; many terrarium pet owners can attest to this, as springtails are specifically bred and kept in “bioactive” captive reptile homes to aid in health and waste breakdown. Some of them could even be described as cute – take Symphypleona for example, globular springtails, which are very reminiscent of an animated character.
A few very special species of Collembola are considered true snow lovers, and may appear as hopping specks of dirt on a snowy landscape. Scientists still aren’t sure exactly why they congregate and become active on the snow, but some hypothesize it’s a form of small-scale migration or a response to excess moisture. Homeowners will occasionally report springtails as pests when this happens even though their populations, no matter how large, do not actually cause any damage to homes. We should probably be thanking them for the ways they are useful to humans. Besides their services in soil health, their brand of anti-freezing chemical genius has been studied for possible human applications like preservation of organs.
Winter midge. Photo by Sarah Witcher
What can these tiny, hidden wonders of winter tell us? For starters, winter is not a time of death or silence for as many living things as we may have thought. Some invertebrates, in fact, wait every year for cold weather to perform some of the most vital functions in their life cycles. Not only are they predators for some and prey to other interconnected species, these creatures provide undeniable benefits to us as humans inhabiting their home ecosystems. Snow fleas, stoneflies, and countless other winter-active species are susceptible to damage from pesticides and other chemical use, so use pesticides sparingly or not at all, even in cold weather. Also, these species suggest that no effort to create habitat in our home landscapes is ever wasted. We may not see immediate, large-scale results when we plant a native plant or tree, but the interconnected communities of wild things we support are there whether we see them or not. Our winters are undoubtedly changing as global climates change, altering the lives of all living species. Whether on a small scale in our gardens or a large scale in the rest of our world, we can all do our part to preserve and protect natural resources like these.
For more ideas for creating habitat in your backyard, visit the Wild Acres pages.
