Ecology On the Ground Floor

Here's a shot from a week or so ago:

Snow Flea (Hypogastrura nivicola),
Illinois Beach SP, Lake Co, IL  5/4/2014

This tiny little guy (~ 2 mm long) is a springtail. I think it's Hypogastrura nivicola, but I wouldn't be surprised to be wrong.

Here's a couple of more springtails:

Homidia socia, Van Patten Woods FP, Lake Co, IL 3/11/2012

This is Homidia socia, identified by the guys at Bugguide.net. He was floating on the surface of a little spring stream.

Sminthurinus henshawi, Van Patten Woods FP, Lake Co, IL 3/29/2014

This one is, I think, Sminthurinus henshawi, also found floating on the surface of that little spring stream. That behavior is actually normal for some springtails. Others live in spaces in the soil, or in downed logs. (Hypogastrura nivicola is also called a Snow Flea. It's not a flea, of course, but it is often found on snow.)

Springtails are arthropods, placed in the order Collembola (at least by some authorities). Despite the six legs, they aren't considered insects these days. They are also incredibly common, especially for critters that most people have never heard of. Joel Greenberg reports on three nearly unbelievable outbreaks that illustrated this. (1) One in Europe actually held up a train by coating the tracks so thickly that the wheels simply spun. One at Northwestern University was estimated at 9 million individuals per square meter. Apply that number to a 1976 occurrence in South Holland that covered two city blocks, and you end up with about 275 billion individuals! What sort of numbers actually live in our forests and fields?

Those sort of numbers have to have some important ecological effects, and a few observers have documented this. For instance, Hanlon and Anderson found that Folsomia candida grazed efficiently enough on fungus that they reduced fungal populations and thereby favored bacterial populations instead. (2)

I remember reading somewhere that we stand about halfway between the size of an atom and the size of the universe -- a remarkable stat. Among living things, however, we're decidedly on the large side, and it's easy to forget that the sorts of ecological processes we see at our scale are happening at the smallest scales as well.

(1) Greenberg, J. (2002) A Natural History of the Chicago Region. University of Chicago Press, Chicago.

(2) Hanlon, R. D. G., & Anderson, J. M. (1979). The effects of Collembola grazing on microbial activity in decomposing leaf litter. Oecologia, 38(1), 93-99.