Rusty Crayfish

Adult rusty crayfish can reach 10 centimeters (4 inches) in length, although they reach maturity at about 4.4 cm (1.7 in), and can range in color from greenish grey, to reddish brown, They can be recognized by two "rusty", reddish colored spots variably present on the sides of their posterior carapace and their large front claws with black bands around the tips. Male astacoid crayfish have small hook-like features, or copulatory stylets, that are used to hold onto a female while mating, prominent in rusty crayfish on the ischia of the third pair of pereopods for those males in their form I (reproductive) molt.

Many species of vertebrates that live in communities together utilize a dominance hierarchy to establish order, and studies have shown that some species of invertebrates do as well. The dominance hierarchy is an important aspect of a crayfish's biology and behavior. Crayfish tend to form dominance hierarchies with the other members of their population in a particular environment. The largest male will generally demonstrate the most dominance over the others by being the most aggressive, and picking fights with the other, smaller crayfish. The crayfish that wins the most fights is placed at the top of the hierarchy with the other members generally ranking in descending order based on size and sex. Studies have suggested that the largest determining factor in the formation of dominance hierarchies is size rather than sex. That means that female rusty crayfish can rank higher in the dominance hierarchy than male rusty crayfish if they are larger than them.