The progressively restricted expression of the transcription factor Atonal underlies the regular spacing of ommatidia in the Drosophila compound eye. Atonal expression, which is initially present throughout the eye imaginal disc, becomes restricted to individual ommatidial founder cells. It has been debated whether the Egf receptor (Egfr) is involved in this process. Now, on p. 4697, Rodrigues and co-workers conclude that it is not. Experiments with a temperature-sensitive null allele of Egfr(Egfrtsla) originally indicated that Egfr had no role in ommatidial spacing. However, the discovery of spacing defects in eyes in which Egfr-null clones were induced using the mosaic Minute+ technique changed this view, leading to suggestions that Egfrtsla was not a true null allele. Rodrigues et al. now genetically and biochemically show that Egfrtsla is functionally inactive at the restrictive temperature, and also report that the Minute+ technique artefactually disrupts ommatidial spacing. Thus, they conclude, Egfr has no primary role in ommatidial founder cell specification or spacing.