Mating and territorial behavior have important fitness consequences. In this thesis, I investigate some processes that affect mating and territoriality in damselflies of the genus Hetaerina. In the first chapter, I carried out an experiment to mimic the initial stage of female color polymorphism, which is hypothesized to be maintained by negative frequency-dependent selection caused by male mating harassment. I tested how males respond to novel female color in a non-polymorphic species, Hetaerina capitalis, and the results supported the mating harassment-based hypotheses. In the second chapter, I experimentally evaluate the ability of rubyspot damselflies to discriminate between neighbors and non-neighbors. Specifically, I tested whether the dear enemy phenomenon (DEP) or a nasty neighbor effect (NNE) governs how territorial males respond to intruders. Two of the three species tested exhibited DEP, but one uses location cues to discriminate intruders while the other uses individual recognition.