Abstract: The mechanism proposed for the isolation of two sibling species of damselflies, Enallagma pollutum and Enallagma signatum, is a tactile isolation based on the shape of the male anal appendages that are used to hold the female during tandem formation. Dissertation Discovery Company and the University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Reproductive Behavior and Isolation of Two Sympatric Coenagrionid Damselflies in Florida" by Kenneth Joseph Tennessen, was obtained from the University of Florida and is being sold with permission from the author. A free digital copy of this work may also be found in the university's institutional repository, the IR@UF. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation.