Order Sphaerotheriida

At first glance, sphaerotheriidan 'pill millipedes' resemble the introduced 'pillbug' slater Armadillidium vulgare, which is an isopod crustacean. Pillbugs and pill millipedes are both capable of rolling up tightly into a ball to defend themselves. Tasmanian sphaerotheriidans are in family Sphaerotheriidae, genus Procyliosoma. Although Silvestri (1917) named and described Procyliosoma leae and P. tasmanicum from Tasmania, neither species can be easily recognised among the many specimens in collections. A third, undescribed species (pictured below, centre) is our largest pill millipede. It has a very restricted range on the East Coast but is well-conserved in the Douglas-Apsley National Park, where it is abundant.

Pill millipedes from Lamington National Park in Queensland (left), the East Coast south of St Marys (centre) and the Arve forest west of Geeveston (right). Scale bar = 10 mm.

Procyliosoma are surface-active at night in wet forest and can be seen wandering around (and climbing trees!) beginning about an hour after sunset. During the daytime they seem to prefer sheltering in richly organic humus, as can be found under stones in dolerite talus and on the floor of long-unburned forest. Nevertheless, Procyliosoma populations recover quickly from fire, and pill millipedes can be abundant in silvicultural regrowth 10+ years old (Mesibov 1997b).

The broad-scale distribution of Procyliosoma in Tasmania is puzzling. Although the genus is widespread, there are patches on the map from which it is apparently absent. The distribution picture may become clearer when individual species are better recognised and carefully mapped.

Localities for Procyliosoma spp.  Scale bar = 100 km.

More information:
 
Taxonomy - Silvestri (1917), Jeekel (1986)
Biology - Hopkin & Read (1992)
Distribution, conservation and general - Mesibov et al. (1995), Mesibov (1997b)