Fig. 13

An adult mouthpart phenotype with medial fusion of labial palps in Tribolium castaneum resulting from larval RNAi knockdown of the genes homothorax (hth) and extradenticle (ext). The example represents a more severe case in the transformation of the loss of labial glossa and paraglossal elements, significant size reduction of the mentum (mnt) and prementum, and fusion of the labial palps into a single medial structure. Abbreviations for maxillary elements are: crd, cardo; stp, stipes; plf, palpiger; lac, lacinia; and gal, galea. Abbreviations for labium are: plg, paliger, lp3 labial palp segment 3. This figure was redrawn from Fig. 1P of Smith and Jockusch (2014) [53]