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.
Very little is known about the fiddler crabs on the Pacific coast of Guatemala and inferring distributions into this area is particularly complicated.
Five species are distributed both north of Guatemala in Mexico and south of Guatemala in El Salvador and are thus presumably also found in Guatemala:
The complication comes from the fact that there are two additional species found in southwestern Mexico and up to 19 additional species found in central to northern El Salvador and we do not know how many of these, if any, are present in Guatemala. Guatemala is essentially a transition zone between the Mexican fauna to the north and the Central American fauna to the south, but we lack the data to know how and where that transition occurs.
Because of this uncertainty, rather than creating a separate guide for the fiddler crabs of the Pacific coast of Guatemala at this time, I would suggest using the guides to the adjacent regions as alternatives: