The medium-sized, dark brown striped emeralds have some pale markings on the thorax and abdomen, black legs, clear wings and brilliant green eyes. The thorax has a metallic bronze-green sheen and the abdomen is dark metallic black-green. Most species are uncommonly seen, but this may be largely due to their secretive nature. When flying, most species look alike which is why in-hand identifications of their anatomical features are often needed.
One of the largest striped emeralds, the lake emerald's length varies from 2.2 to 2.7 inches long. The thorax is brown with possible small yellowish stripes. The hairs on the thorax are longer than other emeralds. The abdomen is black with narrow white rings between all segments.
Ranging through southern Canada and northeastern United States, the lake emerald can be found at boggy lakes, lakes, ponds, and sometimes large rivers. In Wisconsin, it is known from just a few lakes in northern counties.
Throughout its range, the typical flight season is from mid-June to early September.