Woodlice and landhoppers
Woodlice are terrestrial crustaceans in the order Isopoda
. They have many common names, often distinctly regional, such as slaters, pillbugs, sowbugs, cheeselogs, chiggy pigs and grammerzows. They have seven pairs of legs and their upper surface is covered by a hard segmented exoskeleton. They breathe through modified legs known as pleopods on the underside of the rear end of the body. They need to be moist to breath, and their carapace is much less waterproof than an insect's waxy cuticle, so most can only live in damp places out of the sun. Unlike insects, woodlice have a copper-based oxygen-carrying blood pigment analogous to vertebrate haemoglobin. Because of this, they need to eat their own faeces to be able to take in copper from their food released by their gut bacteria.
Most species are 10-20mm long when mature but some are as small as 3-4mm. The common species are mostly grey in colour but sometimes have paler or darker markings, or can be pinkish brown. Pillbug woodlice, Armadillidium
spp., can curl up into a spherical shape when threatened. The pill millipede
, Glomeris marginata
, behaves in a similar way and makes a convincing imitation of a pillbug woodlouse. The pill millipede, however, has shorter antennae and 17-19 pairs of legs.
Species in Britain and Ireland
More than fifty species of woodlice have been recorded in Britain and Ireland but 13 of these are introduced species that live in heated glasshouses. Some species are coastal or have specialised habitat requirements, such as woodland or heathland. About 10 species are commonly found in gardens. Woodlice need dark, damp conditions during the day, so they hide in the surface layers of the soil, in leaf litter, and under logs, stones and flower pots.
recorded 8 woodlice species in her garden, from 6 families, of which the commonest were the common shiny woodlouse Oniscus asellus
, the rough woodlouse Porcellio scaber
, the common pygmy woodlouse Trichoniscus pusillus
and T. pygmaeus. The common striped woodlouse Philoscia muscorum
and Armadillidium vulgare
were occasional. She also encountered the unusual blind white ant woodlouse Platyarthrus hoffmanseggi
which lives in association with ants, in her case Lasius niger.