This key consists of pairs of opposite choices or descriptive statements. To use this key, start at the first page and read the two statements. Decide which statement best describes the organism and click on your choice. This will take you to the next pair of statements. Repeat the procedure until the macroinvertebrate is identified. You can then click on the macroinvertebrate name and additional information concerning the identification, life history, and pollution sensitivity of the macroinvertebrate will be provided.