Abstract: The field cricket Gryllus rubens is well suited for studying how natural and sexual selection interact to favor variation in male sexually-selected traits. In addition to attracting females, the calling song of male G. rubens also attracts gravid females of the parasitoid fly Ormia ochracea. These female flies deposit larvae on and around calling males, killing infected crickets within 7-10 days. In northern Florida, fly parasitism rates are higher in the fall than in the spring. This dissertation examines variation in male calling behavior in G. rubens and evaluates how that variation may be related to seasonal changes in natural and sexual selection. Dissertation Discovery Company and University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Temporal Variation in Natural and Sexual Selection of Male Calling Behavior in the Field Cricket Gryllus Rubens" by Manuel J. Velez, was obtained from University of Florida and is being sold with permission from the author. A digital copy of this work may also be found in the university's institutional repository, 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.