The Atlas covers the northeastern part of the North American continent (south to Virginia, west to the Ontario/Manitoba border, Minnesota, Wisconsin, Illinois and Kentucky). Ninety-two established and six adventitious species are covered by 13 keys from the subfamily to the species level. Keys are accompanied by 437 Figures (mostly high resolution colour photographs) illustrating all important diagnostic characters. Species pages include a set of standard images (636 colour photographs in total) showing lateral and dorsal aspects as well as male and female heads, complemented by images of live specimens where available (many provided by Bugguide contributors!). The variation, distribution and biology of every species is discussed. The work is accompanied by a glossary of scientific terms, and morphological structures are furthermore illustrated in a separate Morphology section. The Atlas is designed both for the amateur and the professional user. With 492 pages, 3 Tables and 1073 Figures (PDF version). An electronic paper published in the Canadian Journal of Arthropod Identification No. 5 (19 February 2008). ISSN 1911-2173. Provided in HTML and PDF format. Available online (free access) at http://www.biology.ualberta.ca/bsc/ejournal/ejournal.html.