Biology of autogenous horse flies native to coastal California: Brennania hera (Diptera: Tabanidae)

Brennania hera, a psammophilous tabanid native to California coastal sand dunes, was studied in Marin County in 1975-82. Immatures were found at depths of 8-40 cm and at a mean density of 3.88/m2 in sandy-silty soils colonized by such plants as Mesembryanthemum chilense, Grindelia stricta and Lupinus arboreus. Egg masses averaged 175.2±58.5 eggs; the incubation period in the laboratory was 9 days. Hovering by males appeared to be governed by temperature, and was functionally related to mating. The intermittent nature of male hovering was an effective anti-predator behaviour. Receptive females flew through the hovering zone in a low, direct, rapid flight. When caught by a male, the pair immediately landed, and coupling averaged 2 min 10 sec. Development of full clutches of mature eggs without a blood meal demonstrated that the population studied was autogenous during the 1st gonotrophic cycle.