To evaluate male mating mistakes, I will observe mating attempts toward a live focal female with her legs cemented to a dowel (“damsel-on-a-stick”) placed near the water at a pond where both E. ebrium and E. hageni are common. Multiple trials will be performed separately with females of each species. Males that attempt to take the female in tandem (the mating position in which the male grasps the female’s thorax with his cerci, the appendages at the end of his abdomen) will be captured either after the female refuses to mate and he releases her (unsuccessful mating attempt, which usually occurs within 2 minutes) or the female curves her abdomen up to the male’s to initiate mating (successful mating attempt). After capture, males will be identified to species by inspection of the cerci with a hand lens. Successful and unsuccessful tandem attempts will be recorded, with the prediction that while males will attempt both conspecific and heterospecific tandems, successful tandems will be more likely between conspecific pairs. An additional study of male mistake rate which allows increased experimental control will occur in an insectary, using fluorescent dust as described by Xu and Fincke (2011). Here, 20 males of one species will be field-caught in the morning and fluorescent dust applied to their cerci and penis. Different males will receive different colors of dust and each color will be applied to an equal number of males. Males will then be released in the insectary with 12 field-caught females of each species. In the afternoon, females in the insectary will be collected and inspected in the lab under a dissecting microscope. Dust on the mesostigmal plates on a female’s thorax indicates that she was taken in tandem by a male and the dust was transferred from his cerci. If the same color of dust is also present on the female’s abdominal tip, this indicates that mating occurred. This method will allow me to discern the proportion of male mating attempts with a female of the wrong species, as well as determine whether any of them were successful. I will do this experiment using both E. ebrium and E. hageni males separately. To test the hypothesis that males can learn to discriminate between E. ebrium and E. hageni females after experience with both, a modification of the insectary/dusting experiment described above will be performed. Twenty males of one species and 12 females of each species will be caught in the field and released in an insectary with food and a small pool water for oviposition. For two days, males and females will be free to mate. After this learning period, males will be captured in the morning and fluorescent dust applied to their cerci and penis in the same manner as described above. In the afternoon, females will be transported to the lab to inspect their mesostigmal plates and abdominal tips for dust. If males learned to identify which females they can and cannot mate with during the two-day learning period, then I predict to find more dust on females of the same species as the males being tested. This experiment will be performed separately with male E. ebrium and E. hageni. Xu, M and Fincke, OM (2011) Tests of the harassment-reduction function and frequency-dependent maintenance of a female-specific color polymorphism in a damselfly. Behav. Ecol. Sociobiol. 65, 1215-1227