Homozygous embryos become abnormal during gastrulation; the germband twists and extends laterally rather than extending dorsally as in wild-type embryos. Significant gaps are seen in the dorsal trunk of the trachea. Somatic myotubes are often not attached to target epidermal attachment sites. This defect is most commonly seen in the ventral oblique muscles located in the anterior most segments of the embryo. Random disorganisation of myotubes and areas without myotubes are also occasionally seen.