The gaps in the expression pattern Tc-wg in the mandible and maxillary endites suggest the mandible is composed of one endite. All views are ventral with anterior to the left. Gene expression was detected by in situ hybridisation. (A) Fully extended germ band stage embryo. Tc-wg is expressed in parasegmental stripes and in the medial region in the ventral ectoderm of each developing appendage. Expression is continuous throughout the medial part of each appendage including the developing endites. (B) Germ band retracting stage embryo. There is a gap of Tc-wg expression in the mandibular endite (black arrowhead) and two gaps in the maxillary endites (black arrows). A white arrowhead marks the boundary between the inner and outer lobes which is lacking Tc-wg expression. A white arrow shows where there is a lack of ectodermal expression in the developing maxillary lacinia. Mandibular (Mn), maxillary (Mx) and labial (La) segments are indicated.