Presence of a stridulatory apparatus in larval stages of woodlice (Isopoda, Oniscidea).

Armadillo officinalis Duméril, 1816 is a terrestrial isopod species belonging to the family Armadillidae, widespread in the Mediterranean basin and on the western coasts of the Black Sea. The species is adapted to live in a xeric environment and has mainly nocturnal habits. A. officinalis is capable of producing vibrations, a characteristic known since the last century. In both sexes, these vibrations are produced by a ridge of scales situated on the propodus of the fourth and fifth pereopod. This character is present in all species belonging to the genus Armadillo. The presence of a similar stridulatory organ in a species of the genus Cubaris from Nepal was indicated as well. The main goal of this study is to find out in which larval stage this organ develops. The manca stages (I, II, III) of Armadillo officinalis are described for the first time and all show the presence of a rudimental stridulatory organ that may be of importance, in terms of adaptation to terrestrial life. Notes on the reproductive biology are shown. Furthermore, some considerations on A. officinalis as a model species in different fields of ecology are also discussed.