This guide is designed for identification “in the field” where you might be looking at live crabs by eye or through binoculars or from photographs. I will generally try to avoid characters that will require you to physically catch the crab, although I may mention a few for secondary verification. It does not include the more strict taxonomist-style characters that may only be visible under a microscope or via dissection. It is also assumed that the individuals are living, as death (and even capture) can cause dramatic color change.
This is a guide to the fiddler crabs of the southeastern Gulf of Mexico, including the states of Tabasco, Campeche, and Yucatan (Quintana Roo is covered in the guide for the Atlantic Coast of Central America). The southeastern Gulf of Mexico has a complex mix of species as it sits at the transition between the Gulf of Mexico to the north and west and the Caribbean to the east. Species found in this region include:
Note: This guide is not complete. While most are described, a few of the species are obscure enough that I do not currently have enough information to reliably describe their appearance or how they differ from some of the other overlapping species.