Fig. 2. kropf mutant larvae display a feeding defect. (A) Wild-type first instar larva fed with red dyed food (feeding assay). The food is predominantly found in the midgut. The multi-layered proventriculus is transparent (arrow). (B) In homozygous kropf mutant larvae, the food is stuck at the proventriculus (arrow). (C) Magnification of the proventriculus of the wild-type larva shown in A. Note that the ectodermal cells (ec) have migrated into the endodermal pouch (en, arrows). (D) Magnification of the proventriculus of the kropf mutant larva shown in B. Note that the ectodermal cells (ec) have failed to move into the endodermal pouch (en; arrows). As a result, the red food is stuck in the oesophagus causing a feeding defect.