Consider a grapsid crab (Metopaulias depressus) that lives in dry areas of Jamaica and exhibits an extraordinary degree of maternal care. Analagous to many amphibians, the larval stages of this crab still require water, but the reservoir of choice is restricted to small ponds. These are not scattered across a beneficent landscape but located in the axils of an epiphytic plant belonging to the bromeliads. It is hardly a propitious place, the water being quite acidic, depressingly low in oxygen, and lacking calcium, something of a disadvantage given that it is essential for the crabs’ skeletons. The mother, however, is definitely in charge. Not only does she clear the pond of debris, but she maintains oxygen levels and never at a loss supplies calcium by the expedient of dumping snail shells that make the nursery more alkaline. Moreover, while she will collect the shells when she comes across them, if the conditions deteriorate, then extra shipments are organized. Given this degree of maintenance it is unsurprising that maternal care extends to feeding the young and protecting them.

really cool tidbit about animal parenting from The Runes of Evolution: How the Universe became Self-Aware. as much as carcinisation is a concept you hear about everywhere, I'm realizing I don't know much about crabs, especially not the land-dwelling (and tree-dwelling!) ones.

Wikipedia link of crab described above.