Here's why:
* Blue whales are mammals. They breathe air, give birth to live young, and nurse their offspring with milk.
* Arthropods are a diverse group of invertebrates that have a hard exoskeleton, segmented bodies, and jointed limbs. Examples include insects, spiders, crabs, and lobsters.
Blue whales, like all other whales, belong to the class Mammalia, while arthropods belong to the phylum Arthropoda.