Which order is wingless hexapods characterized by two long tails (cerci) on the abdomen and monocondylic mandibles?

• A. Diplura
• B. Protura
• C. Collembola
• D. Ephemeroptera

Answer: (A)

Two long tails (cerci) at the end of the abdomen are a hallmark of Diplura, a primitive group of wingless hexapods. Along with monocondylic mandibles, where the jaw attaches to the head by a single articulation, this combination uniquely identifies Diplura among the wingless hexapods. The other groups lack this exact pairing: Protura lack prominent tails and have highly simplified mouthparts; Collembola have a springing organ and different head-mouth part structure; Ephemeroptera are not wingless in their adult stage and have a different jaw articulation. So the two cerci plus monocondylic mandibles point to Diplura.