Originally included as an order of the class Scyphozoa (Jellyfish), the Cubozoa or "Box Jellyfish" are now considered to warrant separate class status. As with the Scyphozoa the medusa is the dominant phase in the life cycle. They differ from Scyphozoa in that they have a velum like structure, the velarium, the bell has four flattened sides and a simple margin, and each polyp produces a single medusa by complete metamorphosis. The name refers to the cubic form of the organism. They occur in tropical and subtropical oceans. There is only one order, the Cubomedusae.
The name sea wasp is also applied to some species of cubozoans, including Chironex fleckeri and Carybdea alata, and are found in Australia, the Philippines, and many other tropical areas. Their venom is among the most deadly in the animal kingdom and has caused at least 63 recorded deaths since 1884. However not all species of Cubomedusae are venomous.
The venom of cubozoans is distinct from that of scyphozoans, but is similarily used to catch prey (fish and small invertebrates) and for defense from predators. Turtles, however, are unaffected by the sting and eat box jellyfish.