What are the three body regions of an adult insect?

• A. Head, Thorax, Abdomen
• B. Head, Thorax, Carapace
• C. Cephalothorax, Abdomen
• D. Head, Abdomen, Thorax

Answer: (A)

Insects have three main body regions: the head for sensory organs and mouthparts, the thorax which bears the legs and often wings, and the abdomen that houses most internal organs and the reproductive system. This three-part division is the standard way to describe an adult insect’s body.

Carapace isn’t a feature of insects; it’s a term from crustaceans and some other groups referring to a protective covering. The cephalothorax is a fused head and thorax found in arachnids like spiders and some crustaceans, not in insects, so that term doesn’t describe insect anatomy either. Listing the three regions as head, thorax, abdomen is the conventional order, though saying head, abdomen, thorax still names the same three regions.