I tried taking a picture of them but taking a close-up picture of snow on a bright, sunny day was too much for the autofocus in my digital camera. I did grab a clump of snow and bring it to my shady deck where I snapped the following.
The black spots are the snow fleas. Here's a cropped close-up:
A little fuzzy. Here's an image I grabbed off the web from someone with a much better camera setup than I have available:
Cofrin Arboretum Center for Biodiversity, University of Wisconsin - Green Bay
I dropped some of the snow fleas in rubbing alcohol so we could look at them under the microscope and see the furcula, the forked structure they fold under their abdomen which allows them to spring up into the air (hence their common name of springtails).
http://www.cals.ncsu.edu/course/ent425/compendium/collem.html (click to enlarge)
Snow fleas are springtails or Collembola (their taxonomic order). Remember basic biology - Kingdom, phylum, class, order, family, genus, and species. The mnemonic I give my college students is Kinky People Come Over For Good Sex (much more memorable than those ones about King Philip coming over).
Springtails obviously belong to belong to kingdom animalia. Their next level of classification is phylum arthropoda - animals with an exoskeleton, a segmented body, and jointed appendages. They include all the insects, spiders, crustaceans (e.g. lobsters, shrimp, crabs), and extinct organisms like the trilobites (among many other things). Arthropods are the most abundant animals on Earth (because of the insects).
They also belong to the hexapoda - some refer to this as a subphylum, others as a superorder - which are the arthropods with three pairs of legs attached to their thorax. This includes all the insects (as well as a few other things). Springtails are placed into class entognatha rather than class insecta because they have internal mouthparts (that's what entognatha means - "internal jaws") unlike the true insects.
Springtails belong to order colembolla which is what they're often called by entomologists. The snow fleas we see in our backyard are likely family Hypogastruridae and belong to the species Hypogastrura nivicola.
The most notable characteristic of springtails is the furcula I've aleady mentioned. It's a forked "tail" they can tuck it under their abdomen and when it's released it catapults them into the air. They typically live in soil and leaf litter in untold numbers and eat plant matter, fungi, algae, bacteria, roundworms and other little critters, and tree sap. In turn, they're eaten by beetles, mites, centipedes, ants, spiders, and other predatory insects.
About the only time most people see springtails is in the early spring when they come out onto the snow on warm, sunny days to feed and mate. My backyard, evidently prime snow flea habitat, has billions of them speckling the snow.
How can these "insects" (not using the term in the taxonomic sense but simply to denote little six-legged critters) survive on snow? It's not like there are other bugs out and about this time of year. Turns out they have an antifreeze-like protein in their little bodies that keep them from freezing up. Research into this protein may make better ice cream as well as enabling better storage of transplant organs.
Most people have never noticed snow fleas and some even think you're pulling their leg when they first hear of them ("Fleas on snow, yeah right!"). If I teach nothing else to my homeschooled kids, having them be observant and intellectually curious is one of my main goals.