Watering:

Following new growth after the winter months, the plant can then be watered. The plant benefits from the pot drying out before being watered again and during the summer months it should be watered every couple of weeks or more. During the winter months the plant can be kept dry.

Source: House Plants Expert

See also:

• Lithops Succulent: How To Grow Living Stone Plants
• The Encyclopedia of Succulents

Scientific classification

Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Aizoaceae
Subfamily: Ruschioideae
Tribe: Ruschiae
Genus: Lithops

                         – Wikipedia.