New giant pill-millipede species from the littoral forest of Madagascar (Diplopoda, Sphaerotheriida, Zoosphaerium)

Two new species of the Malagasy sphaerotheriid genus Zoosphaerium, Z. villosum sp. nov., and Z. arborealis sp. nov., are described. Characters of a shiny black new putative species of the genus Zoosphaerium are described and illustrated. Zoosphaerium alluaudi DeSaussure & Zehntner is redescribed. The characters defining the genus Zoosphaerium are summarized: three jointed anterior telopods, first joint with a stridulation organ termed 'harp' composed out of 1-2 stridulation ribs. Females with stridulation ribs on the subanal plate, termed 'washboard'. Operculum of female vulva constricted in the middle ('subreniform'). 6(th) joint of antennae of cylindrical shape. The nomenclatural history of the genus name is discussed. The intraspecific variability of many characters commonly used to delineate species within the genus Zoosphaerium and other members of the order Sphaerotheriida is analyzed in detail. Ontogenetic changes in the female vulva and the male telopods are discussed and illustrated.