Trichopetalidae

Distinguished from other Chordeumatida families by the combination of 28–30 adult segments and specific gonopod morphology. Within the family, subfamilies are distinguished by generic composition: Mexiterpetinae contains only Mexiterpes, while Trichopetalinae contains the remaining genera (Trichopetalum, Zygonopus, Scoterpes, Causeyella, Nannopetalum, Trigenotyla). Genus-level identification relies on ecological habit (surface vs. cave-dwelling) and detailed gonopod structure.

Adults have 28 or 30 segments (including collum and telson). Members of the genus Trichopetalum produce a sticky secretion from the bases of segmental setae, possibly serving a defensive function. Spermatophores have been described for at least one species (Trichopetalum dux), representing the first authenticated chordeumatidan spermatophores.

Ecologically heterogeneous. Trichopetalum species are surface-dwelling or troglophilic (cave-edge dwelling). Zygonopus and Scoterpes genera consist entirely of troglobitic (obligate cave-dwelling) species. Causeyella species are troglobitic in southern Ozark caves. Mexiterpes occurs in Mexico. Cave-dwelling species occupy deep cave systems, often in specific microhabitats such as moist rocky areas near waterfalls.

North America, with records from Alabama, Georgia, Illinois, Indiana, Kentucky, Tennessee, Virginia, West Virginia, the Ozark Plateau region, and Mexico. Specific cave systems in the Appalachian Mountains and Ozark Plateau harbor multiple troglobitic species.

Causeyella species have been studied under laboratory conditions, though specific behaviors are not detailed in available sources. Trichopetalum species produce a sticky secretion from segmental setae bases, possibly defensive. Immature cave-dwelling individuals may construct larger webs when positioned deeper in caves to compensate for reduced prey availability—this behavior is inferred from observations of a predator (Meta ovalis spider) preying on Causeyella millipedes.

Troglobitic species serve as prey for cave-dwelling predators, including the cave orbweaver spider Meta ovalis (Tetragnathidae), which has been documented preying on Causeyella millipedes. They contribute to nutrient cycling in cave ecosystems through detritivory.

Subject of cave biology and biospeleology research due to high endemism and restricted distributions. Some species likely represent "superspecies" complexes with genetically isolated populations, making them important for studies of subterranean evolution and conservation. Fauna of caverns is poorly known, and many species may be endemic to single cave systems.

• Other Chordeumatida familiesTrichopetalidae is distinguished by 28–30 adult segments and specific gonopod morphology; other families in the order may differ in segment number or reproductive structures.
• Surface-dwelling vs. cave-dwelling Trichopetalidae generaWithin the family, ecological habit differs markedly: Trichopetalum is surface/troglophilic while Zygonopus and Scoterpes are obligate troglobites with convergent adaptations to cave life.

• millipede
• Diplopoda
• Chordeumatida
• cave-dwelling
• troglobitic
• troglophilic
• North America
• subterranean
• biospeleology

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Spider Sunday: Cave Orbweaver
• The milliped family Trichopetalidae, Part 2: The genera Trichopetalum, Zygonopus and Scoterpes (Diplopoda: Chordeumatida, Cleidogonoidea)
• Laboratory observations on the behavior of two troglobitic millipede species in the genus Causeyella (Chordeumatida: Trichopetalidae) from the southern Ozarks