What is the difference between the external structure of the May beetle and the external structure of the crayfish?

The May beetle has three pairs of legs, one pair on each of the three breast segments. Each leg consists of several movable segments and ends in claws with which the beetle clings to the leaves and bark of trees. In addition, the beetle digs the ground with its front legs, where females lay eggs. This is why these legs are very strong and resemble sturdy scrapers.
In crayfish: The body of crayfish, like other arthropods, is externally covered with a strong chitinous cuticle. It is impregnated with calcium carbonate, which gives it extra strength. Outside the aquatic environment, crayfish quickly dry out and die, since the integuments of the body do not have an external waxy layer and therefore do not interfere with the evaporation of water.