What makes an insect different from other arthropods?

• A. Exoskeleton
• B. A thorax
• C. Wings
• D. The presence of antennae

Answer: (D)

Antennae serve as a primary identifying feature for insects because they use a single pair of sensory antennae to explore their environment, which helps set insects apart from many other arthropods. While all arthropods have an exoskeleton, that trait is shared across the group and doesn’t differentiate them. A thorax is common to many arthropods and isn’t unique to insects. Wings are not universal to all insects, so they can’t reliably distinguish the entire class. In contrast, arachnids lack antennae, and crustaceans typically have more than one pair available for sensing. The presence of a single pair of antennae is a practical feature that, in simple classifications, helps separate insects from other major arthropod groups.