iroDFM3clones within the notum territory can fuse together. Clones null for the Iro-C (iroDFM3) or lacking the arm-lacZ transgene were visualized by the absence of green or red, respectively. Homozygous iro+/+ and arm-lacZ+/+ twin clones were detected by the intense green and red signals, respectively. Both types of clones were induced simultaneously at 48 to 72 h AEL. (A-A") Imaginal wing disc displayed many arm-lacZ- clones and twin spots in both the notum (n) and the wing and hinge regions (w). iroDFM3and their corresponding twin spots were also quite numerous in the wing region, but only one iroDFM3clone (arrow) and a few non-associated twin spots (arrowheads) were present in the notum. (B-B"). Close up of an iroDFM3clone. Its cells are either arm-lacZ+/- (arrow) or arm-lacZ+/+ (arrowhead). (C) Wing disc displaying in the notum region a large iroDFM3clone (asterisk, compare with clones in the wing and hinge region). The clone is associated with a large twin spot (arrowhead).