Dev Genes Evol (2009) 219:427–435 433 Fig. 4 Expression of Distal-less, dachshund, and homothorax in Sp8/9 RNAi embryos. a, b Wild- type Dll expression in the head region (a) and the thoracic legs (b). c, d Expression of Dll in Sp8/9 RNAi embryos. Please note that the brownish staining in the head and the bases of all appendages (including the mandibles) in (c, d) is unspecific background sometimes produced during the staining procedure. Embryos in (a)–(d) are at the retracted germband stage. Note the expression in the tips of the maxilla and labium (arrowhead and arrow, respectively, in (a) and (c)). Also note the expression in a distal "sock" and a proximal "ring" in the thoracic legs (arrow and arrowhead, respectively, in (b) and (d)). e–g Expression of dac in wild-type (e) and Sp8/9 RNAi embryos (f, g). Please note that the embryo in (f) has been damaged during preparation (the head has come off and the t1 leg is damaged). The embryos in (e) and (f) are at the retracted germband stage and the embryo in (g) is at an even later retracted germband stage. h–i Expression of hth in wild-type (h) and Sp8/9 RNAi embryos (i). Both embryos are at the retracted germband stage. All animals are oriented with the anterior end to the left. Abbreviations: hl head lobe, lr labrum, an antenna, md mandible, mx maxilla, lb labium, t1 prothoracic leg, t2 mesotho- racic leg, t3 metathoracic leg, pl pleuropodium