The current biodiversity crisis makes the quantification of the diversity and the description of organism distribution particularly pressing. Biological inventories are among the most effective ways to improve the knowledge about local biota, but they can be very time and money‐consuming. The determination of adequate sampling effort and the selection of cost‐effective collecting methods are critical issues. In this article, a spider diversity inventory in an Atlantic semi‐deciduous forest fragment in Brazil was used to compare the efficiency of three collecting methods in two different seasons in order to propose an optimised sampling protocol. The worthiness of increasing sampling effort in the target area and similar tropical ecosystems was estimated and evaluated in terms of its cost‐effectiveness. For a better sampling of the spider community, it is suggested that a proportion of 55, 29 and 16% of total sampling hours should be dedicated to nocturnal hand collecting (NHC), pitfall traps and beating trays, respectively, in the rainy season. If only one method can be applied, the most efficient in terms of species per sampling is the NHC. A completeness of 70% of the estimated spider species richness (as predicted by the Chao1 estimator) was observed in the complete inventory and increasing sampling effort in the studied area may be highly ineffective when the costs involved are considered. Other studies in similar tropical rainforest areas also presented completeness around 70%, which might be a threshold from which the sampling effort necessary to raise the observed species richness substantially starts to be ineffective.

The chelodesmid genus Odontopeltis Pocock, 1894, is revised. It currently contains eight species, four of which are described as new here: Odontopeltis aleijadinho sp. nov., Odontopeltis donabeja sp. nov., Odontopeltis tiradentes sp. nov., and Odontopeltis xica sp. nov. Additional descriptive data are provided for Odontopeltis anchisteus Hoffman, 1981, Odontopeltis clarazianus (Humbert & deSaussure, 1869), Odontopeltis giganteus Schubart, 1849, and Odontopeltis conspersus (Perty, 1844); for the latter species a neotype is designated herein. The current position of all species ever associated with the genus is presented. Examination of type material revealed that the following species are not members of the genus Odontopeltis: Odontopeltis balzanii Silvestri, 1895, Odontopeltis borellii Silvestri, 1895, Polydesmus gracilipes Humbert & deSaussure, 1870, and Odontopeltis proxima Silvestri, 1895. The type specimen of Rhacophorus decoloratus Koch, 1847, is lost and the species is considered incertae sedis. The terminology of gonopod structures is discussed. A phylogenetic analysis of Odontopeltis based on 47 morphological characters, with species of the genus Odontopeltis and six outgroup taxa is presented. Odontopeltis is monophyletic, with Rondonaria as its closest sister-group. The included members of the tribe Telonychopodini (Pantanalodesmus, Telonychopus, and Manfrediodesmus) form a monophyletic group; the tribe Macrocoxodesmini (Macrocoxodesmus and Eucampesmella) is paraphyletic in this data set.

The chelodesmid genus Atlantodesmus Hoffman, 2000 is revised and considered a senior synonym of Iemanja Hoffman, 2000. Currently the genus contains five species, all of them are herein redescribed: Atlantodesmus eimeri (Attems, 1898), Atlantodesmus itapurensis (Schubart, 1943), Atlantodesmus pickeli (Schubart, 1946), Atlantodesmus pintoi (Schubart, 1946), and the transferred species from Iemanja, Atlantodesmus teresa (Hoffman, 2000), new combination. The female of Atlantodesmus teresa is described for the first time. Examination of the type material of Leptodesmus buecherli Schubart, 1955 revealed that this species is a junior synonym of A. itapurensis. A key to males and a distribution map of all species are included.