Flies are uncoordinated showing frequent leg crossing and wings held up or out. Walking and righting ability is impaired. Spontaneous or induced (by light or mechanical stimuli) activity is vigorous. Mechanoreceptor potentials are invariably absent in thoracic macrochaete bristles. The sound evoked response (measured via the antennal nerve) is eliminated. ERGs are normal.

Larval behavioural phenotype: homozygous larvae have very low sensitivity to touch. Homozygous larval motility is visibly reduced. Adults can neither stand nor walk so die by adhesion. Nervous system morphology is indistinguishable from wild type. Gyandromorph mosaics were used for the bristle scratch test to test the mutant mechanosensory bristle function, the tegular and abdominal bristles fail to elicit the scratch response.