Lake darner (Aeshna eremita) is the largest mosaic darner (genus Aeshna) in North America. It is a late-season dragonfly, flying to the end of September. It is found throughout Canada, the northern United States, and the Rocky Mountains. In Minnesota it is fairly common in the northern third of the state.
The adult hunts mostly during the day but also sometimes at dusk. It is a strong flier but does not hover during flight. When hunting it cruises above the water surface with its abdomen slightly arched. It often feeds in swarms, sometimes in great numbers, often with other dragonfly species. It often perches vertically on tree trunks, rarely on the ground.
There are at least ten blue darner dragonfly species found in Minnesota and they are notoriously difficult to tell apart in the field. Lake darner is distinguished by its large size, the first lateral thoracic stripe that is deeply notched and has a dot in the notch, and a black line through the upper face.