Mictyris longicarpus, the light-blue soldier crab, is a species of crab that lives on sandy beaches from the Bay of Bengal to Australia; with other members of the genus Mictyris, it is "one of the most loved crabs in Australia". Adults are across, white, with blue on their backs, and hold their claws vertically. They feed on detritus in the sand, leaving rounded pellets of discarded sand behind them. The males may form into large "armies" which traverse the beach at low tide, before the crabs dig into the sand to wait for the next low tide. Description Mictyris longicarpus is nearly spherical, with an upright body. Its carapace is powder blue, with the rest of the body being white except for purple patches on the joints of the legs. The chelae (claws) are slim and curve downwards, and are held vertically in front of the crab. Given the crab's upright posture, the eyestalks are short. The body is up to across, or "about the size of a cherry". Distribution Mictyris longicarpus is found from Singapore and the Bay of Bengal to New Caledonia and Australia, reaching as far south as Perth, Western Australia in the west, and around the coast of Queensland and New South Wales to Wilsons Promontory, Victoria. Ecology Examination of the gut contents of M. longicarpus showed that the crabs mostly feed on detritus, and any small organisms in the sand, such as diatoms, gastropod eggs, or nematodes. Predators of adults include Threskiornis spinicollis (straw-necked ibis), Todiramphus sordidus (Torresian kingfisher), Egretta alba (great egret), Tetractenos hamiltoni (common toadfish) and Metopograpsus messor (a grapsid crab). The soldier crabs are also attacked by the ghost crab Ocypode ceratophthalma and the moon snail Conuber sordidum. Behaviour Mictyris longicarpus spends much of the time buried in the sand. They emerge to the surface a few hours before low tide, although some individuals may remain submerged for the entire tidal cycle. The first sign that a crab may emerge is the development of "hummocks" which appear on the surface of the sand and increase in size over a period of 10–30 minutes. The number of crabs which emerge is influenced by temperature, wind and rainfall, with the different sexes responding differently, such that one day, nearly all the emerged crabs will be male, while the next day, there may be a mixture of males and females. Emergence of a population from