What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?

Explanation

Success of arthropods is largely due to their unique cuticle, segmentation and jointed appendages. The cuticle is composed of proteins and the polysaccharide chition. It may be strengthened by deposition of minerals in it. It protects the arthropods against predators. It forms jointed exoskeleton for muscle attachment. Being light, it does not add to body weight. It is impervious to water so it checks drying up of the body. This has enabled the arthropods to survive on land in almost any environment. The chitonous wings of the insects enable them to fly and cross barriers which other animals cannot cross. Striated muscles provide quick movements and tracheal respiration supplies energy raply. So arthropods constitute the largest group of the animal kingdom.