The Mormon cricket (MC),Anabrus simplex (Orthoptera:Tettigoniidae),has a long and negative history with agriculture in the western states of the USA where MC often migrates in large groups and causes significant damage to forage plants and cultivated crops.In this review, virulence to MC of isolates of the insect-pathogenic fungus Metarhizium anisopliae varieties acridum and anisopliae were compared in an effort to identify isolates with promise for use as MC biological control agents.All of the isolates tested induced 100% or nearly 100% mortality by six days post application of the fungal conidia.Searches for new Metarhizium isolates with high heat and UV-B tolerance included isolation fungi from field-caught MC and grasshopper after they died in the laboratory and culturing fungi from soil samples collected from numerous western USA sites.The survey was preceded by development of a dodine based selective medium that,at 0.002% active ingredient,permitted growth of M.anisopliae var.acridum,but inhibited most contaminating fungi.The M.anisopliae var.acridum isolates examined to date have much higher tolerance to heat and UV-B irradiation than M.anisopliae var.anisopliae isolates,and this may be critical to successful field applications.The variety acridum has not yet been found in the USA,so our search for such isolates continues.Several new M.anisopliae var.anisopliae and Beauveria spp.were found,and the Metarhizium isolates are being characterized as to stress tolerance and virulence to insects.Characterization includes comparisons of new and pre-existing Metarhizium isolates by amplified fragment-length polymorphism (AFLP) analysis.Finally, experiments on MC developmental biology were conducted to gather data needed to develop a degree day model and to establish laboratory colonies of MC. The Mormon cricket (MC), Anabrus simplex (Orthoptera: Tettigoniidae), has a long and negative history with agriculture in the western states of the USA where MC often migrates in large groups and causes significant damage to forage plants and cultivated crops.In this review, virulence to MC of isolates of the insect-pathogenic fungus Metarhizium anisopliae varieties acridum and anisopliae were compared in an effort to identify isolates with promise for use as MC biological control agents. All of the isolates tested 100% or nearly 100% mortality by six days post application of the fungal conidia. Search for new Metarhizium isolates with high heat and UV-B tolerance included isolation fungi from field-caught MC and grasshopper after they died in the laboratory and culturing fungi from soil samples collected from numerous western USA sites. The survey was preceded by development of a dodine based selective medium that, at 0.002% active ingredient, permitted growth of M. anisopliae var.ac ridum, but inhibited most contaminating fungi.The M.anisopliae var.acridum isolates examined to date have much higher tolerance to heat and UV-B irradiation than M.anisopliae var. isisopliae isolates, and this may be critical to successful field applications. variety acridum has not yet been found in the USA, so our search for such isomains continues.Several new M. anisopliae var. anisopliae and Beauveria spp. found in, and the Metarhizium isolates are being characterized as to stress tolerance and virulence to insects. Characterization includes comparisons of new and pre-existing Metarhizium isolates by amplified fragment-length polymorphism (AFLP) analysis. Finaally, experiments on MC developmental biology were conducted to gather data needed to develop a degree day model and to establish laboratory colonies of MC.