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Johngarthia planata (Stimpson, 1860) is an abundant and ecologically important land crab, distributed on East Pacific islands from the Gulf of California to Colombia. However, despite possible dispersal of planktotropMc larvae by sea currents, J. planata is not known from inshore islands and mainland of Central America. In this study, the presence of J. planata on Costa Rican inshore islands is reported for the first time, strongly supporting the significance of coastal currents for the distributional patterns of such species. Despite the proximity of the Costa Rican inshore islands to the mainland coast and larval dispersal by passing coastal currents, /. planata was not found in mainland locations. We suggest that a high diversity of continental land crab predators excludes /. planata from the continental mainland habitat, while the closely related Gecarcinus quadratus may have adaptations to high prédation pressure. RESUMENJohngarthia planata (Stimpson, 1860) es un cangrejo terrestre abundante y ecológicamente importante, que se encuentra en islas del Pacífico Oriental desde el Golfo de California a Colombia. Sin embargo, a pesar de la capacidad de dispersión de las larvas planctotróficas de J. planata no se conoce de islas cercanas a la costa o de la costa de América Central. En este estudio, se informa, por primera vez, de la presencia de J. planata en Costa Rica en islas cercanas a la costa, apoyando la importancia de corrientes costeras en los patrones de distribución de la especie. Aún así, J. planata no se encontró en el continente, a pesar de la cercanía de las islas costeras y su posibilidad de dispersión por corrientes. Sugerimos que la alta diversidad de cangrejos terrestres depredadores en el continente excluyen J. planata de habitats allí, mientras que Gecarcinus quadratus, una especie relacionada, puede estar adaptada a altas presiones de depredación. ' ) Present address: Bolivian Collection of Fauna,

Sympolymnia, a new genus of myrmecomorph jumping spider belonging to the tribe Simonellini Peckham, Peckham & Wheeler, 1889, is described. It comprises five species: the type species, Sympolymnia lucasi (Taczanowski, 1871), comb. nov., Sympolymnia lauretta (Peckham & Peckham, 1892), comb. nov., Sympolymnia edwardsi (Cutler, 1985), comb. nov. and Sympolymnia shinahotasp. nov. and S. cutlerisp. nov.Sympolymnia lauretta (Peckham & Peckham, 1892) is recorded from Bolivia for the first time. Ontogenetic shifts of ant-resemblance are observed: Juveniles of S. cutlerisp. nov. and S. lauretta mimic black ants of the genus Crematogaster Lund, 1831, but those of S. shinahotasp. nov. most closely resemble Pseudomyrmex ethicus (Forel, 1911). Adults of S. cutlerisp. nov., S. lauretta and S. shinahotasp. nov. resemble the ant Camponotus sanctaefidei Dalla Torre, 1892 and orange adults of S. shinahotasp. nov. are putative mimics of Camponotus latangulus Roger, 1863.

In this contribution a new species of the land crab genus Gecarcinus Leach, 1814, from the Neotropical Pacific coast of South America is described and illustrated. In addition to its unique body color, Gecarcinus nobilii sp. n. is distinguished from congeners by a distinctly wider carapace front and differences in the shape of the infraorbital margin. The new species is not isolated from Gecarcinus populations from the Pacific coast of Central America by an insurmountable geographic barrier. Considering the closure of the Panamanian Isthmus as a calibration point for morphological divergence between the trans-isthmian mainland populations of Gecarcinus, the virtual lack of morphological differentiation (other than color) between them and the distinctness of G. nobilii sp. n. suggests that G. nobilii sp. n. evolved from a common ancestor before the Isthmus closed.

Myrmecotypus tahyinandu sp. n. is described from the Bolivian Chiquitano forest, and M. niger Chickering, 1937 is recorded from Bolivia for the first time. The morphological differentiation among the closely related M. tahyinandu sp. n. and M. iguazu Rubio & Arbino, 2009 is likely attributable to the selection for specific ant mimicry. Adults of M. tahyinandu sp. n. are accurate mimics of the ant Camponotus crassus Mayr, 1862, M. iguazu of C. sericeiventris (Guérin-Méneville, 1838), and M. niger of Dolichoderus bispinosus (Olivier, 1792). This study is the first to identify ant models for morphologically closely related Castianeirinae, providing a promising starting point for future research on ant mimicry.

A new species of Gecarcinidae MacLeay, 1838, Johngarthia cocoensis n. sp. from Cocos Island (Costa Rica) is described and illustrated. The new species closely resembles J. malpilensis (Faxon, 1893), from which it can be separated by the inner apical lobes of the third maxilliped meri mostly separated from each other in resting position, palp of third maxilliped merus partly exposed and epistomial carapace tooth completely exposed.

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A new calyptrate fly mimicking species of Gymnognathus Schönherr 1826 from the humid Tucuman-Bolivian forest in the southern Bolivian Andes is described. Gymnognathus barclayi sp. nov. is distinguished from the closest related species G. bohlsi Jordan, 1895, by the color and/or distribution of the scales on the pronotum, fourth ventrite and pygidium, the wider pronotum and the development of the spines on the pygidium. The arrangement of the longitudinal stripes on the pronotum suggests that G. barclayi sp. nov. is a mimic of tachinid or muscid flies. The almost exclusive occurrence of Gymnognathus species in tropical moist forests indicates that the presence of G. barclayi sp. nov. in the subtropical realm is fostered by increased humidity at orographic rain barriers. G. barclayi sp. nov. is possibly endemic to the Tucuman-Bolivian forest. Along with the presence of other endemic species, the discovery of G. barclayi sp. nov. highlights the importance of the Tucuman-Bolivian forest as an endemism hotspot for insects and calls for a re-assessment of the conservation status of this spatially restricted and threatened ecoregion.