Spiny lobsters, also known as langouste or rock lobsters are a family (Palinuridae) of about 45 species of achelate crustaceans, in the Decapoda Reptantia. Spiny lobsters are also, especially in Australia, New Zealand and South Africa, sometimes called crayfish, sea crayfish or crawfish, terms which elsewhere are reserved for freshwater crayfish. Although they superficially resemble true lobsters in terms of overall shape and having a hard carapace and exoskeleton, the two groups are not closely related. Spiny lobsters can be easily distinguished from true lobsters by their very long, thick, spiny antennae, by the lack of claws (chelae) on the first four pairs of walking legs, although the females of most species have a small claw on the fifth pair, and by a particularly specialized larval phase called phyllosoma. True lobsters have much smaller antennae and claws on the first three pairs of legs, with the first being particularly enlarged. Spiny lobsters have typically a slightly compressed carapace, lacking any lateral ridges. Their antennae lack a scaphocerite, the flattened exopod of the antenna. This is fused to the epistome (a plate between the labrum and the basis of the antenna). The flagellum, at the top of the antenna, is stout, tapering and very long. The ambulatory legs (pereopods) end in claws (chelae). Spiny lobsters are found in almost all warm seas, including the Caribbean and the Mediterranean Sea, but are particularly common in Australasia, where they are referred to commonly as crayfish or sea crayfish (Jasus novaehollandiae and Jasus edwardsii), and in South Africa (Jasus lalandii). A new species, Palinurus barbarae was described in 2006. Spiny lobsters tend to live in crevices of rocks and coral reefs, only occasionally venturing out at night to seek snails, clams, crabs, sea urchins or carrion to eat. Sometimes, they migrate in very large groups in long files of lobsters across the sea floor. These lines may be more than 50 lobsters long. Spiny lobsters navigate by using the smell and taste of natural substances in the water that change in different parts of the ocean. It was recently discovered that spiny lobsters can also navigate by detecting the Earth's magnetic field. They keep together by contact, using their long antennae. Potential predators may be deterred from eating spiny lobsters by a loud screech made by the antennae of the spiny lobsters rubbing against a smooth part of the exoskeleton. Spiny lobsters usually exhibit social habit by being together. However recent studies indicate that healthy lobsters move away from infected ones leaving the diseased lobsters to fend for themselves. Many spiny lobsters produce rasping sounds to repel predators. This is done by rubbing the "plectrum" at the base of the spiny lobster's antennae against a "file". The noise is produced by sticking and slipping, in the same way that a violin string is bowed, and is the only example of this kind of sound production in the animal kingdom. Significantly, the system does not rely on the hardness of the exoskeleton, as many other arthropod sounds do, meaning that the spiny lobsters can continue to produce the deterrent noises even in the period following a moult when they are most vulnerable. The stridulating organ is present in all but three genera in the family (Jasus, Projasus and the furry lobster Palinurellus), and its form can distinguish different species.