Ectopic expression of dSTIM in eye imaginal discs results in small eyes with tetragonal packed ommatidia. Scanning electron micrographs (SEM) of adult eyes in wild-type (wt) flies (A, B) and in flies expressing dSTIMFL(D, E) driven by ey.Gal4. Scale bars in A and D represent 100 μm. Eyes expressing dSTIMFLare smaller than wild-type eyes, and at higher magnification are seen to have a square-shaped ommatidial lattice (E) compared to the hexagonal lattice in wild-type eyes (B). Tangential sections reveal no underlying abnormalities in the specification of photoreceptor clusters (C, F). SEM of adult eyes overexpressing dSTIMFLdriven by GMR.Gal4 (G) and lz.Gal4 (H) show a 'shaven' phenotype in both cases, characterized by loss of interommatidial bristles across most of the eye and mild roughening of the eye surface.