forward in such a way that resembles the striking appendage of a praying mantis, gives this crustacean its name. Caldwell et al. classified the raptorial appendage into two categories based on its functional purpose: a smashing appendage or a spearing appendage. The smashing appendage is possessed by members of gonodactylidae and the dactyl contains several short spines. The spearing appendage is possessed by squillids, lysiosquillids, bathysquillids, and a couple gonodactylids; the last group contains both spearers and smashers. "Smashers" are able to use the raptorial appendage with such a force, particularly the gonodactylids, that they are able to smash the glass of double walled aquariums in the laboratory. These smashers are able to use this immense force to kill same-species competitors with one blow. Caldwell et al. describe how two stomatopods generally display severe fighting behaviour when they have an encounter, both between species and within the same species, and males and females display the same level of this behaviour except in breeding season. Most species of stomatopods, regardless of the type of appendage, ordinarily deliver blows during agonistic encounters with the dactyl closed. When the dactyl is open, the result is usually serious injury or death of the opponent. These crustaceans may deliver blows with the dactyl open but generally only in situations of extremely intense fighting displays, which are rare amongst most species. Behaviour that is common during agonistic displays is raptorial appendage display, which is a common behaviour across many taxa. Display and expansion of the raptorial appendage is conducted in order to make the animal appear larger and therefore more threatening to competitors in times of agonistic encounters, and comparable displays in other taxa include teeth baring in canines or horn display in ungulates. This display behaviour is an evolutionarily conserved behaviour in agonistic displays. Evolutionary differences are clear in "smasher" and "spearer" stomatopods who inhabit different substrates and either burrow or do not burrow. Caldwell et al. describe these differences with respect to a behavioural display called a "meral spread". This behaviour is described by these researchers as the most extreme of raptorial appendage displays, and is defined by the elevation of the cephalothorax and antennae and antennules while the raptorial appendage itself is elevated and spread. Interestingly, this meral spread may be displayed dozens of times during an agonistic encounter and Caldwell et al. explain it is used as a method to inhibit actual