Deuteragenia ossarium, or the "bone-house wasp," a newly-discovered species of the insect, builds its nest from the dead bodies of ants.
Ossuaries, resting places for the dead bodies of people, can sometimes be adorned with the bones of defeated enemies, slaves or servants. Biologists believe this behavior is unique among the animal kingdom, or at least extremely rare. This new species of spider wasp was named after the human tombs.
Michael Staab of the University of Freiburg in Germany was researching cavity-nesting wasps in the Gutianshan National Nature Reserve in the Yangtze River Basin of eastern China. His team set up nest traps in the subtropical forest, hoping to observe the behavior of wasps.
Cavity-nesting wasps typically live in small channels or holes in wood. In these, the produce brood cells, where pupae are placed to develop into the next generation of wasps. Walls between these cells normally consist of pieces of plants, bits of soil, resin, and occasional small traces of insect body parts.
Staab and his team discovered the previously-unknown species of spider wasp. Within their nests, ant bodies were used in the construction of the outer vestibular cell. These are constructed by female wasps to close nests after depositing eggs.
Dead ants provide significant protection for the nests, compared to similar species with more conventional nest designs. This is most likely due to chemical signals emanating from the ant corpses. These scents could simply mask the smell of the developing wasps inside, or it could act as a warning signal to predators. Many ant species defend their colonies with devastating attacks that other animals have learned to avoid. The most common species of ant in the walls were Pachycondyla astuta, a fierce insect with a mighty sting, commonly found in the region.
Researchers never directly observed construction of the walls, nor did they see the wasps hunting ants, for use as building material.
"However, due to the very good condition of all ant specimens in the ant chambers, we assume that the wasp must actively hunt the ants and not collect dead ants from the refuse piles of ant colonies," Staab said.
Banded cat-eyed snakes living from Mexico to South America also depend on chemical signals from the defensive insects. They deposit their eggs within chambers occupied by leaf-cutter ants, which defend their nests - and the snake babies - until the tiny reptiles hatch.
Discovery of Deuteragenia ossarium and the nature of their gristly nests of death was published in the online journal Plos One.