What distinguishes crustaceans from insects?

Crustaceans are distinguished from insects primarily by their body structure, particularly the number and arrangement of their legs. Crustaceans typically possess a greater number of thoracic appendages, most commonly characterized by a total of 10 limbs, including 5 pairs of legs. The option referring to 7 pairs of legs could be misconstrued because it includes both legs and additional appendages, which can differ among various species of crustaceans.

Moreover, insects are generally characterized by having three pairs of legs (for a total of six), whereas crustaceans can have more than this, reflecting their adaptation to diverse habitats and lifestyles. This anatomical difference is one of the key factors distinguishing the two groups.

Understanding the fundamental characteristics of these two classes can help reinforce identification skills and biological knowledge relevant to entomology and aquatic biology, making the correct response significant in identifying these groups within the broader scope of invertebrate taxonomy.