There are more than 50 species of millipede in Britain, although some are introduced species that are confined to glasshouses. They vary considerably in size and appearance. Some, like Brachydesmus and Polydesmus species, have flat bodies and might be confused with centipedes. Most other millipedes have long cylindrical bodies. Millipedes can be up to 40mm long and can be black, greyish brown or creamy white. The species most frequently found on plants is the spotted snake millipede, Blaniulus guttulatus. The plants these millipedes are found on have usually had damage initiated by another animal such as a slug. Spotted snake millipedes have a slender, creamy white cylindrical body, up to 20mm long, with a row of reddish dots along the sides of the body. When disturbed, they lie of their side in a coiled fashion.
Millipedes feed mainly on decaying plant material and the associated fungal growth. They will occasionally damage seedlings and other soft growth, such as strawberry fruits, although damage is usually initiated by other animals such as slugs. Millipedes, especially the spotted snake millipede, are sometimes found feeding inside bulbs, potato tubers and on other root vegetables. In this situation, they are enlarging damage initiated by slugs or some other pest or disease. The relatively weak mouthparts of a millipede will make little impression on healthy undamaged bulbs, roots or tubers.