Most crayfish are red all over, but there are some other colors. It has a large cylindrical body and is the largest shrimp in the world (the largest current crayfish is 66 centimeters long and weighs 16 pounds). The carapace is firm and thick, the cephalothoracic armor is slightly laterally flattened, and the anterior lateral margins are not fused with the anterior plate of the mouth except in the family of crayfish, and the lateral margins are not fused with the thoracic abdominal armor and the bases of the thoracic limbs, and the neck grooves are obvious.
The 1st antenna is shorter and smaller, with a double whip. The 2nd antennae have more developed scales. 3 pairs of jawed feet are all exopodial, the steppers are all unibranchial, the first 3 pairs of chelipeds, of which the 1st pair is particularly powerful and thick, so they are also called chelipeds. The last 2 pairs of footsteps simple, claw-like, gills for filiform gills. Lobster head with 3 pairs of tentacles, tentacles near the head thick, tip small and pointed. A pair of tentacles at the outer edge of the head is particularly thick and long, generally longer than 1/3 of the body length.
A pair of long tentacles in the middle of two pairs of short tentacles, the length of about half of the body length. When perching and crawling normally, all six tentacles are extended forward, and if frightened or attacked, the two long tentacles are bent toward the tail to prevent the tail from being attacked.