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 physical violence.