Chironomids, the non-biting midges, "water" they teach us

Commonly referred to as lake flies, midges, blind mosquitos or even muffleheads, Chironomids are a highly diverse family of small aquatic flies with over 8,000 species worldwide. Small, sleek and wormlike, the larva are found in virtually all freshwater habitats worldwide, yet they tend to be overlooked when exploring stream invertebrates, compared to the larger mayflies, stoneflies and caddisflies with their extravagant appendages. Their importance, however, should not be overlooked or underestimated. With high fecundity, chironomids are considered “the rabbits of the aquatic ecosystem”. Their abundance makes them an important link in food webs, as they transform benthic slime into food for small fishes and invertebrate predators.

Different chironomids are able to tolerate different water quality levels, making them great as indicators of stream health. However, they are challenging to identify given the preparation needed to observe subtle morphological features. An ID shortcut is chironomid exuviae, the floating pupal skins left behind when pupae emerge from the water as winged adult flies.

In this talk, Dr. Susan Gresens, Professor Emerita, Towson University, Department of Biological Sciences, will give us a midge eye view of the world, show how they can help us understand water quality stressors, and try to understand causes of “nuisance midge emergence”.

ABOUT THE SPEAKER: My fascination with aquatic invertebrates began as a child exploring the streams and ponds of my great-grandfather’s cow pasture, and other wetlands in upstate New York. My undergraduate studies at SUNY College at Oneonta whet my appetite to study zooplankton for my M.S. at the University of Wisconsin-Madison. After a brief detour into medical research on autoimmune disease in mice, I earned my doctorate in Ecology and Evolution from the University of Chicago, where chironomids kindly supplied the data for my dissertation. During am postdoc at UC-Berkeley I studied a chironomid that is a key link in the trophic cascade from higher level predators to benthic algae. When I joined the Towson University faculty in 1995, I shifted my focus to chironomid diversity in urban stream ecology and biological assessment of water quality.