Fig. 2. Loss of L4 vein and posteriorwards shift of L3 vein in col¹ mutant wings. (A,B) BS (D-SRF in figure) expression in 24 hours APF pupae. The central BS labelling which prefigures the L3-L4 intervein in wild type wings (A) is missing in col¹ pupae (B), confirming the presence of a single central provein in col¹ mutants. (C,D) Ci expression in pupal wings 28 hours APF. The posterior limit of Ci expression bisects the L3-L4 intervein in wild-type wings (C) but coincides with the posterior limit of L3m vein in col¹ wings, indicating a posterior shift in its position (D). Positions of the L3, (residual) L4 and L3m veins are indicated as in Fig. 1.