The dorsal longitudinal muscles of the indirect flight muscles show disorganization in fiber assembly, phenotypes of muscle degeneration and loosely packed fibrillar nature. The flies are rendered flightless. Dorsoventral muscles are wildtype.

Mutants have diffuse dorsal longitudinal muscles (DLMs), the fibres are formed of diffused fibrils, giving the muscle a spongy appearance. The fibres appear to be stumped and brittle in a few cases. The fibres consistently show thinning and reduced volume. There is also consistent posterior degeneration of the fibres and defective fibril assembly. The thoracic cavity appears to harbour a large vacuole. Dorsoventral muscles are nearly normal, showing slight thinning. The jump muscle also shows thinning but is otherwise normal.