Wrapping up Bill Bryson’s book, A Short History of Nearly Everything, I’ve reached the part about why a great number of animals on Earth have yet to be discovered. A chief reason is that so many are so small and easily overlooked. To illustrate this, Bryson has a great bit on the bed mite, which has existed since humans but wasn’t discovered until 1965. [Warning! Not for the squeamish!]
...your mattress is home to perhaps two million microscopic mites, which come out in the wee hours to sup on your sebaceous oils and feast on all those lovely, crunchy flakes of skin that you shed as you doze and toss. Your pillow alone may be home to forty thousand of them. (To them your head is just one large oily bon-bon.) And don’t think a clean pillowcase will make a difference. To something on the scale of bed mites, the weave of the tightest human fabric looks like ship’s rigging. Indeed, if your pillow is six years old—which is apparently about the average age for a pillow—it has been estimated that one-tenth of its weight will be made up of “sloughed skin, living mites, dead mites and mite dung,” to quote the man who did the measuring, Dr. John Maunder of the British Medical Entomology Center.
Awesome! On a less personal and squirm-inducing level, Bryson also gives the example of scooping up a handful of soil from any forest floor. It will contain up to 10 billion bacteria, most of them unknown to science.
Your sample will also contain perhaps a million plump yeasts, some 200,000 hairy little fungi known as molds, perhaps 10,000 protozoans (of which the most familiar is the amoeba), and assorted rotifers, flatworms, roundworms, and other microscopic creatures known collectively as cryptozoa. A large portion of these will also be unknown.