Polyxenus lagurus

Distinguished from other millipedes by: small size (2–4 mm); flattened body; presence of prominent detachable bristles in tufted arrangement; only 13 leg pairs in adults (far fewer than most millipedes); 10 tergites. The bristle brushes on the telson are particularly distinctive. Difficult to distinguish from other Polyxenus species without close examination; P. lagurus is the only Polyxenida species in the British Isles.

Primarily found under bark of dead trees, especially coniferous trees. Also occurs in forest leaf litter, under stones, on rocks, and on old stone or brick walls. In coastal regions, found at roots of halophile plants and on lichens and moss on boulders. Associated with pine needle litter in Mediterranean conifer formations.

Holarctic distribution. Europe: widespread, most common polyxenid species; only Polyxenida representative in British Isles. North America: recorded in Massachusetts, New York, New Jersey, Ohio, Michigan, Illinois, Colorado, Montana, Arizona, Washington (USA); Nova Scotia, Québec, Ontario, British Columbia (Canada). Introduced to Melbourne, Australia.

Most easily found at night, especially in humid conditions. Also active during daytime in warm, dry conditions and direct sunlight.

Believed to feed on lichens, algae, and small fungi based on habitat associations and authority opinion.

Development through hemianamorphosis: juveniles hatch with 3 leg pairs and 4 tergites, then add segments and legs through seven molts, reaching adult form with 13 leg pairs and 10 tergites in eighth stage. Intermediate stages possess 3, 4, 5, 6, 8, 10, 12, and 13 leg pairs. Adults continue to molt without adding segments or legs.

Nocturnal activity peak in humid conditions; diurnal activity also occurs in warm, dry conditions including direct sunlight. Defensive behavior involves releasing detachable bristles that entangle attacking ants and spiders.

Decomposer; contributes to breakdown of lichens, algae, and fungi in forest ecosystems. Serves as prey for specialized predatory ants, particularly the ponerine ant Thaumatomyrmex in the Neotropics.

Subject of scientific interest due to unique reproductive polymorphism (sexual vs. parthenogenetic populations) and defensive bristle mechanism. Introduced population in Australia indicates human-mediated dispersal.

• Other Polyxenus speciesSimilar small size, flattened form, and bristle coverage; require detailed examination for separation, though P. lagurus is the only species in this genus in many parts of its range (e.g., British Isles).
• Other millipede orders (e.g., Polydesmida, Julida)Distinguished by far greater number of leg pairs (typically 30+ in adults), cylindrical rather than flattened body, and lack of prominent detachable defensive bristles.

• millipede
• bristly millipede
• defensive bristles
• hemianamorphosis
• parthenogenesis
• sexual reproduction
• Holarctic
• coniferous forest
• bark habitat

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Brazil Bugs #12 – Desafio de identificação #5 | Beetles In The Bush
• Aspects of Ecology of Polyxenus Lagurus in Mediterranean Conifer Formations of Greece (Diplopoda: Penicillata)
• Rickettsiales-like microorganisms associated with the Malpighian tubules of the millipede, Polyxenus lagurus (Diplopoda, Penicillata)