Taf1EP421/Taf1XS-2232 flies have reduced bristle numbers on both male and female heads, are female sterile and are semi-lethal. They also display defects in oogenesis, ocelli development, and developmental timing. Ommatidia in Taf1EP421/Taf1XS-2232 flies are irregularly shaped and are not aligned in straight rows. The number of interommatidial bristles are reduced, multiple bristles sometimes originate from a single site and bristles are randomly distributed. The number of photoreceptor cells per ommatidium is also altered in these flies. Approximately 10% of ommatidia re missing one outer photoreceptor, and 14% have an extra outer photoreceptor. Taf1EP421/Taf1XS-2232 flies lack ocelli. Bristles on the thorax show normal morphology but are shifted from the normal orderly pattern. About 5% of Taf1EP421/Taf1XS-2232 males show an abnormal rotation of their terminalia during pupation. Wing development in Taf1EP421/Taf1XS-2232 is also disrupted. The wing vein L4 bifurcates along the wing margin forming a delta. The shape and size of the wings appear normal as does the morphology of the other wing veins. Wings are often held out to the sides of the body rather than crossed over the body as seen in wild-type. Taf1EP421/Taf1XS-2232 females are sterile with very small ovaries. Taf1EP421/Taf1S-625 mothers appear normal in size but eggs laid do not develop. Approximately 5% of egg chambers contain 8 instead of 16 cells.