Mictyris guinotae

Mictyris guinotae has a well-defined subglobular body, slightly less wide than long, a relatively smooth carapace, and long thin legs. They range in color from pale to dark blue, with occasional pale pink variants; they tend to be darker when they are younger and lighter when they are older. The adult male specimens observed had carapaces between 8 and 16 mm long; adult female carapace lengths ranged from 6 to 14 mm.

These crabs live in colonies of hundreds to hundreds of thousands of individuals, in flat lagoon areas of the islands they inhabit. In times of low tide, they form large swarms or "armies" that cross the lagoons en masse, while at high tide they remain under the sand. Their main natural predators are shore birds, and they are sensitive to bird shadows, moving quickly away from them.