The rare Neotropical ant subfamily Leptanilloidinae is revised and its internal phylogeny and biogeography discussed. A new genus, Asphinctanilloides gen.n., including three new species, A. amazona, A. anae and A. manauara, and three new species of Leptanilloides, L. improvisa, L. legionaria and L. sculpturata are described. The only previously known species of the subfamily, L. biconstricta Mann (1923), is redescribed, and the larva of L. legionaria sp.n. is described. Keys to the genera and the species, and a phylogeny of the group are provided. Emphasis has been placed on the study of abdominal and sting characters.

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We describe, for the first time, the predatory behaviour of Thaumatomyrmex ants on millipedes of the family Polyxenidae, based on field observations of T. atrox and a field and laboratory study of T. contumax. The capture of the prey and the removal process of its body-covering setae by the ants before they eat the millipede are described. This specialized behaviour in at least two species of the genus, belonging to two distinct groups of species, indicates a general trend in Thaumatomyrmex. We coupled this study with a comparative morphological analysis of the mouthparts and digestive tube of these and other Thaumatomyrmex species. Also, we report the first case of sympatry in the genus, which suggests that Thaumatomyrmex includes several species, and not only one highly variable taxon, as hypothetized earlier.

Mature nests of the Neotropical myrmicine ant Blepharidatta conops are short blind vertical cylinders, in general excavated directly in the ground. Nurse workers hold the larvae in their mandibles while resting along the nest's walls. When nests are visited or inhabited by myrmecophiles and/or predators, especially Histeridae beetles (adults and larvae), ant workers hide their brood in the nest's subsidiary chamber, the entrance of which is then blocked by the peculiar phragmotic disk of the single ergatoid queen in the colony. The extremely modified head and anterior slope of the pronotum of the queen, that jointly form the almost circular frontal disk, represent a new kind of cryptic phragmosis in ants; exceptional modifications of these structures, which are covered with intricate sculpture, enables the queen to behave as a living gate to the brood chamber, yielding entering nestmates when tapped by them on the disk. Workers use fine grained debris to build a wall at the beginning of the brood's chamber, such that the entrance opening matches the diameter of the queen's frontal disk. Observations in several different Brazilian localities revealed that the queens' frontal disk bear unique locality-specific sculpturing patterns, possibly due to viscous population structures caused by the limited dispersal by virgin queens, whose wing buds never develop.