Volumosina, a new Nearctic genus for the rare old-growth forest fly Herniosina voluminosa Marshall (Diptera: Sphaeroceridae)

Volumosina new genus (Diptera: Sphaeroceridae: Limosininae) is described to accomodate the enigmatic Nearctic species Herniosina voluminosa Marshall, 1987 and its relationships are discussed. Based on morphological characters Volumosina is treated as part of the Limosina genus group along with Apteromyia Vimmer, 1929, Gigalimosina Rohacek, 1983, Herniosina Rohacek, 1983, and Limosina Macquart, 1835 but its position within the group remains unresolved. Volumosina voluminosa (Marshall, 1987) new combination is recorded from Canada and redescribed with new distributional and natural history data suggesting that it is an old-growth specialist associated with large woody debris. The gigantism of the male aedeagal complex of V. voluminosa is discussed.