A Tiny Little Mushroom Connoisseur

Here's a nice find from last summer:

Psychoglypha subborealis, Zion, Lake Co, IL  7/1/2013

This is Psychoglypha subborealis, a large caddisfly (order Trichoptera). Caddisfly larvae are aquatic, and most of them are quite intolerant of pollution, so finding this guy here appears to be a sign that at least some of our local wetlands are in good shape.

Caddisfly larvae are famous for constructing cases out of whatever debris is available around them, binding the stuff together with silk. There's a good deal of variation in this behavior, both in terms of the size and shape of the structure itself and the point in development when it's constructed. Some species wait until they're ready to pupate, but apparently this species builds it's cases soon after hatching.

Caddisflies also vary in their food preferences, with this species being known as a leaf shredder. Arsuffi & Suberkropp looked into this at a finer scale in the 1980's, finding that they preferred leaves that had been colonized by certain species of fungi. (1) Furthermore, the preferred level of pre-digestion by the fungi appeared to vary with the fungal species. They were even able to demonstrate that the larvae are distinguishing between fungi on different parts of the same leaf. (2)

The guiding assumption behind their initial work seems to have been that the processing of the fungi improved the quality of the leaves as a food source. However, further research suggested instead that the larvae actually gain more nutrition from the fungus than they do from the leaves themselves, suggesting that the food preferences they initially reported were based as much on the status of the fungi than on the leaves. (3)

I don't see any larger conclusions to draw from these studies, but this sort of detail is why biology remains such a fascinating topic.

Arsuffi, T. L., & Suberkropp, K. (1984). Leaf processing capabilities of aquatic hyphomycetes: interspecific differences and influence on shredder feeding preferences. Oikos, 144-154.

Arsuffi, T. L., & Suberkropp, K. (1985). Selective feeding by stream caddisfly (Trichoptera) detritivores on leaves with fungal-colonized patches. Oikos, 50-58.

Arsuffi, T. L., & Suberkropp, K. (1988). Effects of fungal mycelia and enzymatically degraded leaves on feeding and performance of caddisfly (Trichoptera) larvae. Journal of the North American Benthological Society, 205-211.