The chironomid fauna living on an exotic macrophyte, Eurasian water milfoil (Myriophyllum spicatum), was studied quantitatively for a year in experimental ponds constructed to simulate reservoir wetlands. A total of 10 species, 2 Orthocladiinae, 5 Chironominae, and 3 Tanypodinae, were recorded. Of these 10 chironomid species, Apedilum elachistum comprised 79% of all chironomid larvae collected on the plants. Annual production of A. elachistum was estimated by the size-frequency method to be 9.9 g dry mass/m²/yr for milfoil surface area, which is among the highest production estimates reported for a single species. Annual production/biomass was 79/yr. Laboratory-reared larvae required an average of 23 days at 15°, 16 days at 20°, and 11 days at 25 °C to complete their development from first instar to imago.