Mantis shrimps, or stomatopods, are marine crustaceans of the order Stomatopoda. Some species have specialised calcified 'clubs' that can strike with great power, while others have sharp forelimbs used to capture prey. They branched from other members of the class Malacostraca around 410 million years ago. Mantis shrimps typically grow to around 10 cm (3.9 in) in length. A few can reach up to 38 cm (15 in). The largest mantis shrimp ever caught had a length of 46 cm (18 in); it was caught in the Indian River near Fort Pierce, Florida, in the United States. A mantis shrimp's carapace (the bony, thick shell that covers crustaceans and some other species) covers only the rear part of the head and the first four segments of the thorax. Varieties range from shades of brown to vivid colors, as more than 450 species of mantis shrimps are known. They are among the most important predators in many shallow, tropical and subtropical marine habitats. However, despite being common, they are poorly understood, as many species spend most of their lives tucked away in burrows and holes. Called 'sea locusts' by ancient Assyrians, 'prawn killers' in Australia, and now sometimes referred to as 'thumb splitters'—because of the animal's ability to inflict painful gashes if handled incautiously—mantis shrimps have powerful claws that are used to attack and kill prey by spearing, stunning, or dismembering. Around 451 species of mantis shrimps have currently been discovered worldwide; all living species are in the suborder Unipeltata. These aggressive and typically solitary sea creatures spend most of their time hiding in rock formations or burrowing intricate passageways in the sea bed. They rarely exit their homes except to feed and relocate, and can be active during the day, nocturnal, or active primarily at twilight, depending on the species. Unlike most crustaceans, they sometimes hunt, chase, and kill prey. Although some live in temperate seas, most species live in tropical and subtropical waters in the Indian and Pacific Oceans between eastern Africa and Hawaii. Mantis shrimp live in burrows where they spend the majority of their time. The two different categories of mantis shrimp – spearing and smashing – favor different locations for burrowing. The spearing species build their habitat in soft sediments and the smashing species make burrows in hard substrata or coral cavities. These two habitats are crucial for their ecology since they use burrows as sites for retreat and as locations for consuming their prey.Burrows and coral cavities are also used as sites for mating and for keeping their eggs safe. Stomatopod body size undergoes periodic growth which necessitates finding a new cavity or burrow that will fit the animal’s new diameter. Some spearing species can modify their pre-established habitat if the burrow is made of silt or mud, which can be expanded.