Little Algal Grazers

Here's a fancy little caddisfly from a couple of years ago:

Caddisfly sp, Zion, Lake Co, IL 7/9/2012

I don't know which species this is, and they're generally harder to ID than moths or butterflies, so I guess I'll have to live with it.

I mentioned in an earlier post that these guys are well-known for constructing cases to live in while they're in their larval form. Well, I've managed a little bit of luck this spring, and here's a couple of examples:

Psychoglypha subborealis, Fort Sheridan FP, Lake Co, IL, 4/5/2014

I think this one's Psychoglypha subborealis, the species I discussed last time around.

Limnephilus sp, Van Patten Woods FP, Lake Co, IL 4/20/2014

This one's in the genus Limnephilus. Identifying it to species would probably involve a microscope at the very least, but taking it down to genus is actually fairly simple, since the case-building techniques are hard-wired into the larvae, and are quite frequently distinctive between genera.

Most caddisfly larvae are grazers on algae, and grazers have impacts on their food, even when they're this small. Lamberti & Resh showed that caddisflies do reduce algae densities, but they increase algal turnover rates, and as a result, areas with caddisflies can support more invertebrate grazers than areas without them. (1) Feminella & Resh showed that when water levels are low, caddisfly larvae are forced into competition with each other, but when water levels increased in the late summer, they were able to spread out and no longer compete directly with each other. (2)

The idea that water level impacts grazer density and therefore both the algal populations and the populations of other grazers is something that I wouldn't have considered, with my admitted terrestrial bias. But it's fascinating, regardless, and suggests that climate change must be causing all sorts of subtle ecological effects we haven't even thought to look at yet.

(1) Lamberti, G. A., & Resh, V. H. (1983). Stream periphyton and insect herbivores: an experimental study of grazing by a caddisfly population. Ecology,64(5), 1124-1135.

(2) Feminella, J. W., & Resh, V. H. (1990). Hydrologic influences, disturbance, and intraspecific competition in a stream caddisfly population. Ecology, 71(6), 2083-2094.