Answer :
Answer:
A plane of symmetry that forms mirror images around a vertical plane in the midline.
Explanation:
Bilateria are animals that have a bilateral symmetry,
Bilateral symmetry refers to organisms that are mirror images along their midline called a sagittal plane.
Examples of bilateria include butterflies and humans because, a line through their midline divides the organism into two identical halves which are mirror images of each other.
So, Bilateria are characterized by a plane of symmetry that forms mirror images around a vertical plane in the midline.