Which organism is not an insect?

Which organism is not an insect?

• A. Sowbug
• B. Aphid
• C. Grasshopper
• D. Beetle larva

Answer: (A)

What this question tests is how to tell insects from other arthropods by body plan. Insects have a body divided into three parts (head, thorax, abdomen) and six legs as adults. The sowbug is a crustacean, not an insect, and it has a multi-segmented body with many legs and two pairs of antennae—features typical of crustaceans rather than insects. The other options are insects: aphids are small Hemiptera with six legs, grasshoppers are Orthoptera with six legs, and beetle larvae are the immature form of beetles, which are insects. So the organism that is not an insect is the sowbug.

What this question tests is how to tell insects from other arthropods by body plan. Insects have a body divided into three parts (head, thorax, abdomen) and six legs as adults. The sowbug is a crustacean, not an insect, and it has a multi-segmented body with many legs and two pairs of antennae—features typical of crustaceans rather than insects. The other options are insects: aphids are small Hemiptera with six legs, grasshoppers are Orthoptera with six legs, and beetle larvae are the immature form of beetles, which are insects. So the organism that is not an insect is the sowbug.