12. Six Legs—No More, No Less
A hallmark of all insects is their six-legged body plan, with every leg attached to the middle segment known as the thorax.
This key feature sets insects apart from other arthropods, such as spiders, which have eight legs, or centipedes with dozens.
No matter how large or small, every insect—from butterflies to beetles—shares this distinctive trait, uniting them as members of the same incredible class.