Fig. 2. Developmental effects of the loss of hth/exd function. (A) Adult notum containing a exd^- clone (arrow) in the lateral region. The clone differentiates several macrochaetes that are not normally present in that zone. (B) A large M⁺ exd^- clone showing alterations of the bristle pattern in the scutellum region and the disappearance of the suture between the scutum and the scutellum. (C) Idealised image of the phenotype of an entire exd^- heminotum (right) compared with a normal heminotum (left). The two sutures are lost and the pattern of macrochaetes is different from the normal one. dc, dorsocentral; pa, postalar; s, suture; sc, scutellum. (D-F) Notum region of the disc containing several hth^- clones, marked black. The red staining marks the activity of the DC enhancer (see main text for details), which is expressed in the precursors of the dorsocentral bristles. The normal activity of this line is indicated in the inset in D. The clone in the posterior region (arrows in D,F) shows ectopic activity of the DC enhancer, indicating a change of the identity towards scutum.