Which characteristic differentiates mites, ticks, and spiders from insects?

• A. One body region
• B. Wings
• C. Three body regions
• D. Two body regions

Answer: (D)

The key idea here is understanding the basic body plan differences between insects and arachnids. Insects have three distinct body regions: a head, a thorax, and an abdomen, and they typically have six legs. Mites, ticks, and spiders are arachnids, which characteristically have two main body regions—the cephalothorax (a fused head and thorax) and the abdomen—and they usually have eight legs. This two-region arrangement is the fundamental feature that sets mites, ticks, and spiders apart from insects. Wings are not reliable for this distinction since some insects have wings while several arachnids never have them. So, the characteristic that best differentiates them is having two body regions.