The "bone house" wasp (Deuteragenia ossarium) is named so because the newly classified species of spider wasp has adopted a unique method of protecting their nests. They simply fill the front hall with ant corpses.
"Bone house" wasps live in the hollowed out cavities of trees and soil. Since the female wasp doesn't care for her brood much beyond constructing the nest, the developing eggs are vulnerable to predation during their gestation period. To minimise the risk of her progeny being discovered before they can fend for themselves, the bone house wasp will fill the nest's front chamber (which is walled off from the individually housed eggs) with as many dead ants as it can hold. This behaviour has never been observed in nature before.
And apparently the technique works. A team led by Michael Staab from University of Freiburg, Germany, collected roughly 800 nests throughout Southeast Asia, 70 of which employed dead ants, and found that the bone house wasp's suffered a significantly lower rate of parasitism compared to their undefended counterparts.
The researchers, who published their findings in the journal PLOS One today, suspect that the decomposing ants might act as pheromonal warnings to other insects -- not unlike the welcoming effect a row of heads on pikes has on uninvited human guests. [Physorg]