Cylindroiulus truncorum

Distinguished from congeners by the truncated (shortened) appearance of the telson (terminal body segment), which gives the species its name. The gonopod morphology in males provides definitive identification; these structures require microscopic examination. Cylindroiulus truncorum lacks the prominent ozopores (defensive gland openings) found in some related genera. It may be confused with Cylindroiulus britannicus or Cylindroiulus caeruleocinctus, but differs in gonopod structure and subtle body proportions. Accurate identification typically requires examination of mature males.

Elongated, cylindrical body with smooth, rounded segments. Coloration ranges from pale brown to reddish-brown, often with darker longitudinal stripes. Males possess modified gonopods (copulatory appendages) on the seventh body segment. Adult length approximately 20–30 mm. Antennae relatively short, composed of seven segments. Ocelli (simple eyes) arranged in a triangular patch on each side of the head. Tergites smooth, lacking prominent keels or tubercles. Leg pairs number two per diplosegment, typical of the order Julida.

Found in deciduous and mixed woodland, particularly in areas with calcareous soils. Occupies the litter layer and upper soil horizons, often in association with rotting wood and humus-rich substrates. Favors moist, shaded microhabitats with moderate to high organic matter content. Has been recorded from parklands, hedgerows, and semi-natural grasslands with woody vegetation.

Native to Europe. Documented from France, Germany, Switzerland, Austria, and surrounding regions. Distribution appears centered on western and central European lowlands and foothills. The iNaturalist observation count of 43 suggests it is encountered infrequently relative to more common congeners, possibly reflecting genuine rarity or under-recording due to identification challenges.

Adults have been observed throughout the year in suitable habitats, with peak surface activity during moist conditions in spring and autumn. Juveniles present in summer months. Activity reduced during winter in colder parts of range, though deep soil habitats may allow year-round persistence.

Detritivore. Consumes decaying leaf litter, rotting wood, and other decomposing plant material. Feeding habits inferred from family-level traits and habitat associations; specific dietary studies for this species are lacking.

Development through anamorphosis: hatchlings emerge with few leg pairs and segments, adding more through successive molts until reaching the adult complement of approximately 50–60 segments. Sexual maturity attained after numerous instars, likely requiring several years. Females deposit eggs in soil or decaying organic matter. Direct development; no larval stage.

Primarily nocturnal surface forager, retreating to soil or litter during daylight hours. When disturbed, coils into a loose spiral rather than a tight ball. Slow, deliberate locomotion using wave-like leg movement typical of julid millipedes. Chemoreception important for locating food and mates.

Contributes to decomposition and nutrient cycling through fragmentation and microbial conditioning of plant detritus. Serves as prey for soil-dwelling invertebrates, small mammals, and birds. Represents a component of soil mesofauna biodiversity in temperate woodland ecosystems.

No documented economic importance. Occasionally encountered by naturalists and soil ecologists. Not known to cause damage to crops or structures. May be incidentally collected in soil samples for ecological research.

• Cylindroiulus britannicusOverlaps in distribution and habitat; distinguished by male gonopod morphology and subtle differences in segment proportions.
• Cylindroiulus caeruleocinctusSimilar cylindrical form and coloration; C. caeruleocinctus often shows more distinct blue-black banding and differs in gonopod structure.
• Ophyiulus pilosusCo-occurring julid with similar size; Ophyiulus species have hairy body surfaces and different gonopod morphology.

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life