The Lake Myvatn ecosystem in northern Iceland is remarkable in that it is so dominated by a single species. Myvatn translates as 'midge lake', and it is the non-biting midge Tanytarsus gracilentus that dominates; comprising two-thirds of the lake's secondary productivity, it is the main food for local fish and birds. Midge numbers undergo extreme fluctuations of almost six orders of magnitude with an irregular period of 4 to 7 years. A new analysis of population monitoring over 25 years shows that this phenomenon can be explained by alternative dynamical states where the amplitude of the fluctuations is set by small subsidies of food entering the habitat. Small decreases in these subsidies due to human disturbances could explain recent increases in midge fluctuations. So in terms of conservation, midge population dynamics are inherently unpredictable and are much more vulnerable to small disturbances in the lake than was expected. The Lake Myvatn midges illustrate the fundamental complexities of natural ecosystems and the difficulties in managing them. The cover photo (by rni Einarsson) shows mating swarms of male midges around the margin of Myvatn waiting for females to fly up into their midst.