Secondary conidia types in the insect pathogenic fungal genus Strongwellsea (Entomophthoromycotina: Entomophthorales) infecting adult Diptera.

Two types of secondary conidia and their formation are described from six species of Strongwellsea infecting hosts from Anthomyiidae, Muscidae and Fanniidae. We used a simple device allowing secondary conidia to be produced under very moist or comparatively dry conditions. Ellipsoid type secondary conidia, which are formed under very moist conditions, have never been reported before from the genus Strongwellsea, and they are unique for Entomophthorales; these are broadly ellipsoidal with a clearly pointed basal papilla and are actively discharged. Subglobose type secondary conidia are, for the first time, described from several species in the genus Strongwellsea; they are subglobose to almost bell-shaped with a flattened papilla and are actively discharged. Subglobose type secondary conidia are formed under more dry conditions. A general pattern of the formation of secondary conidia in Strongwellsea and the ecological roles of primary conidia and of the two types of secondary conidia are discussed.