HARPELLALES - GENERIC CONFUSION DUE TO PRECOCIOUS DEVELOPMENT

The two genera of Harpellales (Trichomycetes) found most frequently in Chironomidae (midge) larvae, namely Smittium in the hindgut and Stach ylina in the midgut, are easily distinguished in most instances. Howev er cases are reported in which Smittium trichospores extrude premature ly as they pass through the midgut, with the sporangiospore attaching to the peritrophic membrane and thereby leading to very limited thalli c growth that resembles an immature Stachylina thallus. This developme nt appears to be common in Smittium longisporum and Sm. perforatum, an d may occur less frequently in some other species of Smittium. Methods to identify such ''false'' Stachylina thalli are discussed.