Insects versus Arachnids, Structurally Distinguished
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State
An insect, a hexapod, has three body regions, six legs, and antennae; an arachnid has two body regions, eight legs, no antennae.
Show
A beetle's head, thorax, and abdomen carry six legs and antennae; a scorpion's fused head-thorax and abdomen carry eight legs and pincers.
Watch for
"Bug," per Bio 2273, blurs these plans — this course reserves "insect" and "arachnid" as precise terms.