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Trechona diamantina sp. nov. is described from quartzite caves in Diamantina, central Minas Gerais State, Brazil. This represents the largest cavernicolous mygalomorph population ever recorded. The new species is the first Trechona recorded from a xeric habitat, namely the Rocky Fields on the Diamantina Plateau. T. diamantina sp. nov. is closely related to T. uniformis, both species possessing elongated male and female copulatory organs and both constructing distinct funnel-webs and sheet-webs in quartzite formations. T. diamantina sp. nov. is distinct in possessing less elongated embolus and receptacula seminis. A key for all valid species of the genus is given.

A new species of Tmesiphantes Simon, 1892, is described from sandstone/quartizitic caves of Chapada Diamantina, Bahia State, Brazil. This is the fifth species of the genus and the first record of a troglobitic mygalomorph in Brazil. A key is presented for all Tmesiphantes species.

A new species of Harmonicon F. O. Pickard-Cambridge, 1896 (Araneae, Dipluridae) is described, from a medium-sized lateritic cave in Parauapebas, Pará, Brazil. The male holotype and only specimen known of H. cerberus sp. n. was found near the entrance of Pequiá cave. This taxon is the fourth species described and the southernmost record for the genus. The new species displays some troglomorphic characteristics, such as reduction and merging of the posterior median and both pairs of lateral eyes and pale yellow to light brown coloration. Both characters are diagnostic when compared to the normal separated eyes and reddish to dark brown of other Harmonicon species. Other diagnostic characteristics are isolated, long, rigid setae distal to the lyra and the shape of the copulatory bulb. This is the second troglomorphic mygalomorph species from Brazil and the first from the Amazonian region.

Diplura C.L. Koch, 1850 is a mygalomorph genus with putative records from Central and South america. The type-species Diplura macrura (C.L. Koch, 1841), originally described from West indies, is poorly known and represented only by its holotype. Most of the 20 species currently included in the genus lack modern taxonomic descriptions, as D. lineata (Lucas, 1857), from Rio de Janeiro state, Brazil. Males and females of Diplura macrura and D. lineata are herein redescribed. New junior synonyms of D. macrura are identified (