develops into embryonic/larval midgut embryonic/larval midgut primordium fused midgut primordium fly_anatomy.ontology The developing larval midgut from the beginning of fusion of the anterior and posterior midgut primordia during stage 12 through the completion of fusion at the dorsal and ventral midlines during stage 15 to the completion of gastric caecum development during stage 16. FBbt:00007593