Stridulation in Crabs is produced by the friction one against the other of two more or less differentiated zones. Schematically, the stridulating apparatus comprises two parts: one termed the pars stridens is adorned in relief which varies according to the species (striae, granules, beadings, rigid hairs, etc.), the other termed the plectrum is most often a raised ridged area or a sharp edge. In
... [Show full abstract] many cases the pars stridens is situated on the ventral surface of the cephalothorax and the plectrum on the cheliped. There are other methods, notably: friction of two segments (propodus and ischium) of the cheliped (Ocypoda), friction of the cheliped against another appendage, reciprocal friction of appendages, or of the chelipeds, etc. The stridulating mechanism is only developed in the Brachygnatha (Brachyrhyncha) and the Oxystomata, but the phyletic relationships between the different families is not apparent in its structure: two related genera or even species of the same genus (Ovalipes) may have very different stridulatory formations. Stridulation can be combined with four types of behaviour: sexual, defence of territory, social and