INSECTS THAT SPEND THEIR TIME ON SNOW  

Thursday, March 17, 2011

It was at the Massassauga Conservation Area where the hiker came upon them a few weeks ago. The photo I received in an e-mail showed indentations in the snow that appeared soiled, rather odd since the trails otherwise appeared to be covered in fresh snow. It was almost as if there had been a fire somewhere and this was black soot that had drifted in and settled in the depressions. But as the hiker drew nearer, the soot began to dance as though activated by some mysterious static electricity. Curious, she took a photo.

Although the air temperature was near zero, the snow was still quite cold and not even close to melting. Still, these were microscopic insects she was witnessing - snow fleas, more accurately known as springtails, and they were in no pain. They’re used to playing in the snow.

Springtails, although resembling fleas as they jump about, are in no way related to fleas. They are so primitive they have no wings, and there is no evidence they ever did. In short, their evolution stopped long before wings came on the scene, and that was a very long time ago indeed. Springtails are aptly named, for that is precisely what they do, with their tail. It is an ingenious piece of equipment, forked and normally bent underneath the abdomen and fastened with a spring release under pressure. If you want the technical name, the appendage is called the furcula - a little fork on the end of the abdomen. When the springtail wants to escape an enemy, it suddenly releases the furcula and and propels the insect upwards, up to 100 times its body length. As they jump around they spread the spores of mosses and fungi that cling to hairs on their bodies. In this way they are probably instrumental in maintaining the microhabitats in which they live.  

We always seem very amazed when we see insects actively moving about in the winter. Woolly bears out on warm winter days never fail to shock us. So what were these snow fleas doing out? Warm winter days draw them out in large masses to feed on algae, organic material and fungal spores on old snowbanks. They are so tiny that 100,000 in a one square metre of surface is not an unusual number. When under the snow, they play an important role in recycling organic material. You can nearly always find a few if you look in the silvery fur of the winter rosettes of mullein. Interestingly, they have a tendency in winter to accumulate in low places; hence, the reason we see them in our foot tracks or ski tracks.  If you want to get a close-up view of these little critters, simply take a look at them through the opposite end of your binoculars, which will turn your binoculars into a handy magnifying glass.

We tend to call them insects, but actually they are not, although they are six-legged and certainly share a common ancestor. Their scientific name, Collembolla from ‘coll’, meaning glue and ‘embol’, meaning peg, refers to a rather fascinating feature about this creature. Don’t attempt to see this feature through the wrong end of your binoculars for you will likely fail in your attempt.  They have a tube which projects down from the underside of the abdomen, and which exudes a glue-like substance for adhesion on slippery surfaces - certainly useful, I would suspect,  if they are out and about on a windy day. That same organ also controls fluid balance in the body.

But springtails aren’t the only minute creatures that are apparent on warm winter days. Flowing creeks often produces stoneflies. Soon after hatching in early spring, the larvae bury themselves in the stream bed. The immature nymphs of these small, dark coloured slender insects live in water, and their name comes from their habit of clinging to the underside of submerged stones. When frigid weather sends virtually all other flying insects to their death, the nymphs of winter stoneflies crawl from under their submerged stones where they have spent the summer, make their way up streambanks, and anchor themselves to rocks with gluelike secretions. Then, they crawl out of their skins, and take to the chilled air as four-winged adults. Check out your local creek and you may see them.  If you are lucky, as I was one day this winter, you may even see one flying at slow, lumbering speeds. They are welcome insects to see since they are indicators of water quality as they thrive only in clear, unpolluted water. In fact, when water-quality surveyors turn up stoneflies in their macro invertebrate samples, they classify the stream as "good quality" because these insects require clean, well-oxygenated water.

By having this rather unorthodox life style, and spending the summer lying dormant while other insects are out and about, they avoid problems like overheated streams, low oxygen concentrations, fluctuating flows, and heavy predation by fish. 

With small birds and large predatory insects fewer in number in the winter than in summer, Springtails may even realize this too as they come out to dance in the snow. Population-wise, it doesn’t really matter if the hiker at Massassauga inadvertently skied or snowshoed over some of the springtails; there were probably eight billion left behind that were untouched.