Polyxenus lagurus (Linnaeus, 1758)

Distribution

Polyxenus lagurus is widespread south of a line from the Severn to the Humber but is increasingly restricted to coastal sites further north. 

Elsewhere the species occurs throughout Europe and also in the Central Sahara and the USA (Enghoff, 1976a; 1978). 

Habitat

It occurs on old walls, on trees and in maritime habitats. In all these situations it is associated with lichens and algae on which it feeds. It can be found most readily by searching at night, especially in humid conditions, when torchlight may reveal aggregations of animals on old stone walls. In maritime habitats it occurs under mats of halophile plants, lichens and moss (Blower, 1985). 

In Belgium the species occurs on old walls but also under bark and lichens on trees (Kime, 2004). Blower (1985) also stated that it was most often found under the bark of dead trees, especially conifers. However, the recording scheme's habitat data suggests a strong negative relationship with woodland. This apparent contradiction is probably explained by the ease of locating the millipede on old walls (relative to the difficulties of searching for it in woodlands) combined with the increased recording effort in churchyards over the lifetime of the recording scheme. Habitat preferences are discussed by Alexander (2006; 2010; 2012); the latter  reporting its occurrence at up to 600 m a.s.l. in the Black Mountains of South Wales.

Phenology

A parthenogenetic and a sexual form of this species are reported from mainland Europe (Schömann, 1956). The British populations that have been examined appear to be of the sexual form (Fussey & Vardnell, 1980). Adults have been recorded between May and September.

This species account is based on Lee (2006).