Pill Millipede

• It is constantly mistaken for the common pill woodlouse, which is a crustacean: the pill millipede has two pairs of legs per segment and fewer dorsal plates, and its ball is smoother and glossier.
• It secretes from pores along its back a sticky, toxic fluid that can immobilise a spider attempting to attack it.
• Its role in breaking down leaf litter is considerable: it processes a substantial fraction of the leaves that fall in a beech wood each autumn.
• It rolls into a perfect ball at the slightest disturbance, just like the common pill woodlouse. It is a classic case of convergence: two very different groups — a myriapod and a crustacean — arriving at the same solution.
• They can be told apart by the legs: the woodlouse has seven pairs and this millipede many more, although fewer than other millipedes.
• It secretes a sticky defensive fluid containing quinazolinones, compounds that act as a sedative on the wolf spiders that try to eat it.
• It is an important decomposer: it shreds leaf litter and speeds its recycling, and its droppings add humus.
• It can live seven years, a long time for a soil arthropod, and matures slowly.

Habitat and environment

Damp leaf litter of deciduous woodland and hedgerows of Europe

Sources consulted: Villers (1789) · Schildknecht et al. · Blower, Millipedes (Synopses of the British Fauna)