Which order comprises flies, with variable mouthparts and two membranous wings plus two halteres?

• A. Diptera
• B. Orthoptera
• C. Hemiptera
• D. Dictyoptera

Answer: (A)

The key idea here is identifying flies by their wing arrangement and the presence of halteres. Diptera are defined by one pair of functional wings, with the hind pair reduced to small structures called halteres that act as balance organs during flight. That combination—two membranous wings and two halteres—plus the fact that mouthparts are highly variable among flies (ranging from sponging to piercing-sucking) is what sets this order apart. The other groups have different flight wing configurations and mouthpart types: Orthoptera typically have forewings that are tougher (tegmina) and jumping hind legs; Hemiptera have piercing-sucking mouthparts and wings that are partly hardened rather than a single pair of membranous wings with halteres; Dictyoptera covers cockroaches and mantises with distinct wing coverings and no halteres. So the description matches Diptera.