Animal life in caves has fascinated researchers and the public alike because of the unusual and sometimes bizarre morphological adaptations observed in numerous troglobitic species. Despite their worldwide diversity, the adaptations of cave millipedes (Diplopoda) to a troglobitic lifestyle have rarely been examined. In this study, morphological characters were analyzed in species belonging to four different orders (Glomerida, Polydesmida, Chordeumatida, and Spirostreptida) and six different families (Glomeridae, Paradoxosomatidae, Polydesmidae, Haplodesmidae, Megalotylidae, and Cambalopsidae) that represent the taxonomic diversity of class Diplopoda. We focused on the recently discovered millipede fauna of caves in southern China. Thirty different characters were used to compare cave troglobites and epigean species within the same genera. A character matrix was created to analyze convergent evolution of cave adaptations. Males and females were analyzed independently to examine sex differences in cave adaptations. While 10 characters only occurred in a few phylogenetic groups, 20 characters were scored for in all families. Of these, four characters were discovered to have evolved convergently in all troglobitic millipedes. The characters that represented potential morphological cave adaptations in troglobitic species were: (1) a longer body; (2) a lighter body color; (3) elongation of the femora; and (4) elongation of the tarsi of walking legs. Surprisingly, female, but not male, antennae were more elongated in troglobites than in epigean species. Our study clearly shows that morphological adaptations have evolved convergently in different, unrelated millipede orders and families, most likely as a direct adaptation to cave life.

A new species of giant pill-millipede is described and illustrated from Guizhou Provinces, southern China: Sphaerobelum huzhengkuni n. sp. This is the first record of the genus Sphaerobelum in China. A molecular phylogenetic analysis of this genus is also provided based on DNA-barcoding of the COI mitochondrial gene.

Five new species of giant pill-millipedes in the family Zephroniidae are described and illustrated from China: Zephronia medogensis Zhao & Liu n. sp., Z. zhouae Zhao & Liu n. sp., Z. hui Liu & Wesener n. sp., Sphaerobelum benqii Liu & Wesener n. sp. and S. tujiaphilum Zhao & Liu n. sp. COI sequences of these five new species are given and deposited in GenBank. Additionally, a study of the genetic distance and a molecular maximum likelihood analysis were conducted based on DNA barcoding data of most SE Asian Sphaerotheriida species.

Seven new species of Epanerchodus Attems, 1901 are described from caves in southern China: Epanerchodus latus n. sp., Epanerchodus tujiaphilus n. sp., Epanerchodus jiangxiensis n. sp., Epanerchodus coniger n. sp., Epanerchodus parvus n. sp., Epanerchodus gladiatus n. sp. and Epanerchodus chutou n. sp. The first three species are from Chongqing, Hunan and Jiangxi, respectively; the last four are from Guizhou. Additional records, illustrations and descriptive notes are given for the following troglobitic species: Epanerchodus lipsae Golovatch & Geoffroy, 2014, from Sichuan; Epanerchodus soror Geoffroy & Golovatch, 2004, from Yunnan; Epanerchodus stylotarseus Chen & Zhang, 1990, from Guizhou; Epanerchodus varius Geoffroy & Golovatch, 2004, from Hubei, Sichuan and Chongqing; and Epanerchodus draco Geoffroy & Golovatch, 2004, from Yunnan and Guizhou. New records of E. varius from Chongqing and E. draco from Guizhou are documented. A key and distribution maps are provided to all 25 species of Epanerchodus currently known to occur in mainland China.

A new species of glomeridellid millipede is described from Guizhou Province, southern China: Tonkinomeris huzhengkuni sp. nov. This new epigean species differs very clearly in many structural details, being sufficiently distinct morphologically and disjunct geographically from T. napoensis Nguyen, Sierwald & Marek, 2019, the type and sole species of Tonkinomeris Nguyen, Sierwald & Marek, 2019, which was described recently from northern Vietnam. The genus Tonkinomeris is formally relegated from Glomeridae and assigned to the family Glomeridellidae, which has hitherto been considered strictly Euro-Mediterranean in distribution and is thus new to the diplopod faunas of China and Indochina. Tonkinomeris is re-diagnosed and shown to have perhaps the basalmost position in the family Glomeridellidae. Its relationships are discussed, both morphological and zoogeographical, within and outside the Glomeridellidae, which can now be considered as relict and basically Oriental in origin. Because of the still highly limited array of DNA-barcoding sequences of the COI mitochondrial gene available in the GenBank, the first molecular phylogenetic analysis of Glomerida attempted here shows our phylogram to be too deficient to consider meaningful.

Located in the core zone of Mulun National Nature Reserve in northern Guangxi, the limestone cave Ganxiao Dong harbours the richest cave fauna currently known in China. In total, 26 species of cave invertebrates have been recognized so far, in spite of limited sampling efforts. Of them, 20 are troglobionts or stygobionts, including one snail, four millipedes, three spiders, one harvestman, three isopods, two springtails, two crickets, one non-glowing sticky worm, and three trechine beetles. Six other species are troglophiles. The most remarkable characteristic of this fauna is its high number of troglomorphic species, especially among millipedes, crickets and beetles.