Hovering and swarming behavior of males of Hybomitra lasiophthalma and Hybomitra aurilimba (Diptera: Tabanidae)

Males of H. lasiophthalma and H. aurilimba hovered and swarmed in a sunlit area of Connecticut during June or July of 1977-82. These activities occurred mainly during mornings and at temperatures of 17-30°C. Males of each species coexisted at hovering sites in low numbers (4-6) during early July, but the frequency of intraspecific interactions exceeded the number of interspecific encounters. Distances between hovering males and frequencies of interactions varied with the number of individuals present. There was no evidence of pair formation or mating. Anthrone reagent detected fructose or sucrose in >43% of the 331 males analysed; rates of sugar positivity were highest (_70%) early in the day.