Which of the following is classified as an arachnid?

Scorpions are classified as arachnids, which is a class of joint-legged invertebrates that also includes spiders, ticks, and mites. Arachnids are characterized by having eight legs, a two-part body structure consisting of a cephalothorax and an abdomen, and lack of antennae. Understanding this classification is important for recognizing the ecological roles that arachnids play, such as pest control and their part in the food web.

In contrast, insects, which include ants, butterflies, and beetles, have six legs, three main body parts (head, thorax, abdomen), and typically possess antennae. This fundamental difference in body structure is key to distinguishing arachnids from insects, thereby clarifying why the correct answer is scorpion, as it fits the criteria for being an arachnid.