Snowfleas seen in March snowpack
As we begin this new month of March, we enter a time that can bring big changes in the weather conditions. Often, this month is thought of as a time of snow storms, and indeed, these days have given us some impressive snows.
Many of us remember the storm of early March 2007, but a few years later, in 2010, the same month produced only a trace of snow for the entire 31 days. Snow, ice, rain, winds, subzero temperatures and balmy days reaching into the 60s are all possible in this changing month. Daylight that begins with 11 hours, reaches 12 shortly after mid-month (March 18) and following the vernal equinox March 20, days have stretched to be 12.5 hours as we exit March.
Thanks to the daylight that we get at this time, I always look for some things to happen at the start of March. The sunlight on these longer days will get absorbed by the dark bark of deciduous trees and get reradiated back out into the surrounding snowpack to warm and melt it, forming circles around the base of the trees. Such "tree circles" are a sign that trees are undergoing other changes as well.
After standing out in the winter devoid of leaves, they feel the sunlit warmth. Sap begins its flow, best known in the maple trees. Some buds, most notable the furry ones of willows and quaking aspen, begin to open now. And if we look at groups of trees along the roadsides, we'll see a tint of color showing up in the twigs of many trees. The upper most twigs of birches take on a burgundy color, hard to see on individual trees, but noticeable when seen with many birches.
Among the smaller trees, willow of various kinds hold twigs that can be reddish or yellowish. And the shrubby red-osier dogwoods are nearly entirely bright red. Rivers may be opening, weeks before the ice goes from the ponds and lakes. Some early migrants of raptors begin to appear with the new month.
But it is still winter. During the first half of this month we experience the deepest snowpack of the whole season. Snows that have accumulated earlier are not yet melted and it may be tough going for some critters in the deep snow.
And though these changes may be happening above, many hibernators are still inactive beneath the snow. But there is more here, too.
The area below the snow and above the ground is known as the subnivean space. Thanks to the warming from the earth and the insulation of the sow, this place is where myriads of critters spend the winter in an active state. This may include mice and shrews, but also insects and spiders. We do not usually see these members of this hidden site unless they journey to the surface.
Since the temperatures at the top of the snowpack are far colder than below for much of the winter, they remain in this relative warm shelter. But during mild days throughout the winter, lots of these insects and spiders will climb up to the surface and move about. I'm not quite sure of the route that they take to get there, but it could be the spaces opened at the base of the trees. And such conditions as this will happen at the beginning of March.
Once we know what to look for, we can see these critters active on the snow now. The list is longer than we may expect and includes a couple of crane flies — some with wings, others without — along with two kinds of spiders: wolf and dwarf.
But the most abundant insects on the snow on mild March days are snowfleas. It is not unusual that as we are passing wooded areas at this time for us to see what looks like a coating of pepper on the snow. Taking a closer look, the "pepper" appears to move. And not just walking; these minute critters are hopping. Yes, we are observing the world of the "snowfleas."
Though they are called fleas, they are not fleas. We are not in any danger of them getting on us or our pets as we get near them. Correctly, they are tiny insects called springtails and belong to a group called collembola.
Like other insects, they have six legs on their tiny bodies (less than 0.1 inch), but unlike most insects, they do not have wings. Using their legs, they move about freely on the surface of the snow when temperatures are in the thirties or forties; but they also jump. Their leaping is not done by legs as expected, but instead they have an appendage called a furcula, near the end of the body, that when released will propel them up. This is why they are called springtails.
Why are they on the surface of the snow during late winter days in such abundance, literally thousands? Apparently, they live under the snow in the leaves and soil of the subnivean space, but now in this mature phase of their lives, they come onto the surface to feed on microscopic algae that grows here on these longer days and here, too, they will find mates.
And so, on some mild March days, it may look to us that the snow has been sprinkled with pepper, but we are watching a phase in the lives of springtails known as snowfleas.