Signaling through the Drosophila EGF receptor (DER) is important for the growth and differentiation of the wing. These processes may be mediated by different DER ligands including Spitz (Spi) and Vein (Vn). Here I investigate the roles of these ligands and other DER pathway components in wing disc development using in vivo culture to produce mutant discs from genotypes which are normally embryonic lethal. I find no role for spi in wing disc growth, whereas vn is essential. spi mutant wing discs are morphologically normal as judged by expression of the vein marker rhomboid (rho) and analysis of the differentiated wing tissue. rho, Star (S) and argos (aos) which are known to be involved in Spi/DER signaling are likewise not required for wing growth, whereas pointed (pnt), which acts at the end of the intracellular pathway, is required. The results suggest different ligands and molecular mechanisms control DER signaling in wing growth and differentiation.