SEASONAL CHANGE IN PLANT-DWELLING CHIRONOMIDAE AND NAIDIDAE IN A WISCONSIN LAKE
We investigated the degree of change in the larval chironomid and naidid communities colonizing the macrophyte Potamogeton nodosus over the plant's growing season. Sampling of plant-dwelling invertebrates at three sites in Eau Galle Lake, Wisconsin near the beginning of the growing season of P. nodosus (June - 1987) and at the peak of this macrophyte's development (August - 1986 and 1987) revealed dramatic seasonal changes in abundance among the chironomid and naidid species. Non-burrowing chironomid larvae (Paratanytarsus sp., Thienemanniella nr. fusca, and Corynoneura taris) dominated the June collections, whereas burrowing chironomids such as Polypedilum illinoense, Glyptotendipes dreisbachi, and Endochironomus nigricans dominated the August collections in both years. Naidids also showed a marked change from June to August; e.g. Nais pardalis, the most abundant naidid on P. nodosus in June, was not present in the August collections. The striking similarities between the August 1986 and August 1987 invertebrate collections (and their dissimilarities from the June collections) also indicate that these seasonal changes are predictable. It is also apparent that the seasonal succession of chironomid and naidid species produces great temporal diversity, since different species use the same plants at different times. Chironomid and naidid species richness on P. nodosus was considerably greater than has been reported from other studies of plant-dwelling invertebrate communities.