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.

Recent discoveries reveal that southern China's karsts hold the most diverse and morphologically modified subterranean trechine beetles in the world, albeit the first troglobitic blind beetle was only reported in the early 1990's. In total, 110 species belonging to 43 genera of cavernicolous trechines have hitherto been recorded from the karsts of southern China, including the following five new genera proposed below: Shiqianaphaenops Tian, gen. n., to contain two species: Shiqianaphaenops majusculus (Uéno, 1999) (= Shenaphaenops majusculus Uéno, 1999, comb. n.), the type species from Cave Feng Dong, Shiqian, Guizhou, and Shiqianaphaenops cursor (Uéno, 1999) (= Shenaphaenops cursor Uéno, 1999, comb. n.), from Cave Shenxian Dong, Shiqian, Guizhou; and the monotypic Dianotrechus Tian, gen. n. (the type species: Dianotrechus gueorguievi Tian, sp. n., from Cave Dashi Dong, Kunming, Yunnan), Tianeotrechus Tian & Tang, gen. n. (the type species: Tianeotrechus trisetosus Tian & Tang, sp. n., from Cave Bahao Dong, Tian'e County, Guangxi), Huoyanodytes Tian & Huang, gen. n. (the type species: Huoyanodytes tujiaphilus Tian & Huang, sp. n., from Longshan, Hunan) and Wanhuaphaenops Tian & Wang, gen. n. (the type species: Wanhuaphaenops zhangi Tian & Wang, sp. n., from Cave Songjia Dong, Chenzhou, Hunan).

Four new species of Desmoxytes are described from southern China: D. lingulata sp. n., D. parvula sp. n., and D. nodulosa sp. n., from Guangxi Zhuang Autonomous Region, and D. getuhensis sp. n. from Guizhou Province. In addition, new records of D. scutigeroides Golovatch, Geoffroy & Mauriès, 2010 and D. scolopendroides Golovatch, Geoffroy & Mauriès, 2010 are provided, with a modified key to Desmoxytes species currently known to occur in China. Two of the new species, D. nodulosa sp. n. and D. getuhensis sp. n., seem to be troglobites.

Six new species of Desmoxytes are described from southern China: D. laticollis sp. n., D. simplipoda sp. n., and D. similis sp. n., all three from caves in Guangdong Province; D. phasmoides sp. n. also from a cave, and both epigean D. spiniterga sp. n. and D. variabilis sp. n., the latter trio from Guangxi Zhuang Autonomous Region. A modified key to all 20 Desmoxytes species currently known to occur in China is given.

Three new species of the genus Guiodytes Tian, 2013 are described from the limestone caves of Guangxi Zhuang Autonomous Region, southern China: Guiodytes weii Huang & Faille sp. nov. and Guiodytes yueliangensis Huang & Tian sp. nov. from Dapo Dong and Huang Dong caves, respectively, in Huanjiang County, northernmost Guangxi; Guiodytes inexpectatus Tian & Zhou sp. nov. from the Zhuzhu Dong cave in Longzhou County, southwestern Guangxi. All of the six known species of Guiodytes are endemic to Guangxi, ranging from the southwest to the northernmost. A modified key to species and a distribution map for Guiodytes are provided.

Four new cavernicolous species of the millipede genus Eutrichodesmus Silvestri, 1910 from southern China (Diplopoda: Polydesmida: Haplodesmidae)