The first case of intranidal phragmosis in ants. The ergatoid queen of Blepharidatta conops (Formicidae, Myrmicinae) blocks the entrance of the broodchamber

Mature nests of the Neotropical myrmicine ant Blepharidatta conops are shor t blind vertical cylinders, in general excavated directly in the ground. Nu rse workers hold the larvae in their mandibles while resting along the nest 's walls. When nests are visited or inhabited by myrmecophiles and/or preda tors, especially Histeridae beetles (adults and larvae), ant workers hide t heir 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 t o 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 open ing matches the diameter of the queen's frontal disk. Observations in sever al different Brazilian localities revealed that the queens' frontal disk be ar unique locality-specific sculpturing patterns, possibly due to viscous p opulation structures caused by the limited dispersal by virgin queens, whos e wing buds never develop.