After a balmy February, winter finally arrived in the mid-Atlantic region recently with several inches of snow and bone chilling temperatures. One of the real delights of a forest walk following a late season snow is the possibility of glimpsing snow fleas, tiny six-legged relatives of true insects. They belong to a part of the arthropod clan called Collembola. Most springtails are only 1 or 2 millimeters long. They are among the most ancient of six-legged creatures. Collembola have been on the planet for roughly 400 million years, millions of years before the first animals with backbones moved from the primordial sea to the land. Snow fleas belong to the genus Hypogastrura. At certain times of the year they become very abundant on the ground or near water. Snow fleas multiply on the forest floor and move about despite chilly temperatures. Their ability to survive subfreezing temperatures is made possible by proteins in their tissues that prevent the formation of lethal ice crystals. They can reach amazing densities and their dark coloration makes them quite apparent on white objects such as patches of snow. Unlike true fleas, which are external parasites of other animals, snow fleas and other springtails eat tiny plants, decaying vegetation, bacteria, and fungi. On one occasion I found a large colony of Collembola happily living inside the water tank of someone’s commode, contentedly grazing on biofilm inside the tank. Exactly how they colonized the tank remains a mystery.
On a brisk day in winter a tiny springtail goes for a stroll. Cryoprotectant proteins shield the springtail from freezing on cold winter days.
In addition to snow fleas, other springtails frequent snowbanks in late winter. The ones featured in this episode belong to the clan known as globular springtails, or Sminthuridae. The propulsion system used by springtails differs from that of their insect relatives. True fleas such as cat and dog fleas have a flexible protein called resilin in their legs. Resilin is compressed and stores energy that is released in a split-second burst to power the jump. Springtails have an odd forked shaped appendage called a furcula. The furcula is tucked beneath the body most of the time and held in place by a clasp called the retinaculum. When danger approaches and a springtail needs a quick escape, the clasp releases the furcula and like a projectile hurled from a catapult, the springtail is propelled through the air. These jumps can be prodigious, sending the springtail a distance many times its body length. At the next opportunity to take a walk in the snowy forest take a moment to have a look for these tiny winter leapers.
The interesting article “Snow fleas: helpful winter critters” by Katie Kline was used as a reference for this episode.