Abstract
The Trichomycetes are fungi that live obligately as commensals in the guts of arthropods. Our studies dealt principally, but not exclusively, with the order Harpellales that inhabit the midgut and hindgut of aquatic larvae of Diptera. Jackson Hole was selected for these studies because of its wealth of Trichomycete material. These fungi were known to be present through work in the area during previous years by one of us. Project Number 104.