Adults bearing two copies of Mhc^R1845W in an Mhc¹⁰ homozygous background present a wings-up phenotype, are virtually flightless, jump significantly shorter distances, and the indirect flight muscles exhibit severe disruptions in muscle fibers, including torn fibers that are bunched at the attachment sites, disrupted sarcomere integrity and accumulation of myosin and poly-ubiquitin aggregates, as compared to controls. At the ultrastructural level, the indirect flight muscles of pupae and young adults lack the normal round morphology, lack the regular sarcomeric arrangement and show misaligned subsections of myofibrils, with several areas showing disruption of the hexagonal arrangement of thick and thin filaments, as compared to controls; these defects are more severe in young adults compared to pupae.