What identifies an ectoparasite as an insect?

• A. 3 body segments and 3 pairs of legs
• B. 6 legs and 1 body segment
• C. More than 6 legs
• D. 2 body parts and 4 pairs of legs

Answer: (D)

Insects are hexapods, meaning they have three body regions—head, thorax, and abdomen—and six legs (three pairs) attached to the thorax. So, an ectoparasite that is an insect will display three distinct body parts and six legs in total. This pattern distinguishes insects from arachnids, which have two body regions (often described as cephalothorax and abdomen) and four pairs of legs (eight legs). Therefore, the identifying feature for an insect among ectoparasites is three body parts with six legs.