Fig. 3. Expression of Dll in embryonic Drosophila limb primordia. Lateral views of stage 11 (A) and 15 (B) Drosophila embryos stained for Dll (green) and Escargot (Esg; red) protein. Anterior is towards the left. Esg is expressed in imaginal tissues that ultimately give rise to adult structures. Dll is expressed in the first to third thoracic segments (T1-T3) in clusters of cells that give rise to both the leg imaginal discs and the larval Keilin’s organs. Dll also is expressed in the precursors of the labral (lr), antennal (an), maxillary (mx) and labial (la) larval sense organs. At stage 15, Dll is expressed in some brain (br) precursors, but appears not to be expressed in head imaginal tissues. The wing (w) and haltere (h) discs express Esg, but not Dll.