Larval instars and growth pattern of a univoltine black fly, Prosimulium kiotoense (Diptera: Simuliidae), in Kyushu, Japan.

Seven larval instars were detected for a natural population of Prosimulium kiotoense Shiraki in Kyushu, Japan, from the size frequency distribution of postgenal lengths. Growth in P. kiotoense larvae followed a geometric progression from first to sixth instars, but the size ratio between sixth and seventh instars was smaller than between other successive stadia. The linear relationship between the mean instar value and daily cumulative water temperature indicated that development between instars required 82.6 degree-days (DD). The accumulated temperature for larval development of this species was estimated to be 600 DD.