Survivorship, Site Fidelity and Weight Dynamics of Male Hybomitra aurilimba (Diptera: Tabanidae) at a Hilltop Mating Arena

I present a mark-release-recapture study of individually marked males of the horsefly <em>Hybomitra</em> <em>aurilimba</em> (Stone) (Diptera: Tabanidae) at a hilltop mating arena in southern Ontario, Canada; the study occupied much of the seasonal on-wing period of the males. Survivorship, population size, daily recruitment and site fidelity were examined by recapture of marked males. Flies were often recaptured on the day of marking and thereafter on up to 7 different days, covering periods up to 16 d following marking. The population was small (&lt;100 males) with a relatively high daily recruitment. The males exhibited pronounced and prolonged fidelity to both the overall mating arena and to individual hovering sites within the arena. Mean daily survivorship was relatively high (0.84 ± 0.021 (SEM)), leading to a mean on-site residency time of 5.7 d (95% CL: 4.4–7.9 d). Marked and recaptured males were weighed; they exhibited highly individual patterns of substantial weight losses and gains, both within and among days.