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General: What is best in life?

Conan: To crush your enemies, see them driven before you, and to hear the lamentation of their women. ~Conan the Barbarian, 1982 Film.

A newly-described wasp species would disagree; what is best in life is to feed your children living spiders, and build a wall around your nursery in which you have entombed the bodies of giant ants. The new species, Deuteragenia ossarium, is named after graveyard ossuaries where thousands of bones are collected.

The "Bone-House Wasp" belongs to a fascinating group of solitary spider predators, the Pompilidae. Female wasps pounce on spider prey and sting; her venom attacks the nervous system of the spider and paralyzes it. Then she drags the body of her immobilized victim back to her nest, a tunnel in the ground or a tubular hole in wood.

A single egg is laid on the spider, and the wasp walls it up alive in a tomb of spit and soil. When the egg hatches, the wasp larva eats the (still living) spider. Whether the spider is considered a sacrifice to Crom is not known.

Spider wasps are notorious badasses. From a 2004 research paper:

Few, if any, people would be stung willingly by a tarantula hawk. I know of no examples of such bravery in the name of knowledge, for the reputation of pompilid wasps... is well known among the biological community. All stings experienced occurred during a collector's enthusiasm in obtaining specimens typically resulted in the stung person uttering an expletive, tossing the net into the air and screaming — such was the immediate pain....

Advice I have given in speaking engagements was to “lay down and scream.” The reasoning being that the pain is so debilitating and excruciating that the victim is at risk of further injury by tripping in a hole or over an object in the path and falling onto a cactus or into a barbed wire fence."*

Spider wasps have little to fear from mammals and our puny vertebrate ways; predation on these wasps is rare. Pompiid wasps are parasitized by other wasps, though, and the new species has an extremely clever (and creepy) way of preventing that.

The bone-house wasps turned up in a project to document forest biodiversity and ecosystem functioning in Jiangxi Province, China. The researchers were surveying solitary wasps in a nature reserve. 829 nests were collected and brought back to the lab to rear out all the larvae. During the process of dissecting and examining the nests, the experimenters noticed something odd.

Some of the nests contained more than just wasp larvae munching on spiders; they had a vestibule (entry compartment) filled with the bodies of dead ants. Spider wasps don't eat ants; in fact, adult wasps mostly feed on pollen and nectar. The spider-catching is all to feed their babies.

The Ossuary of a Bone House Wasp. This photo shows the chambers (A) where the spiders have been walled up as baby provisions, and the "vestibule" (B) containing a barrier of ant corpses. Merten Ehmig (A, B), Michael Staab (C, D). doi:10.1371/journal.pone.0101592.g002

When the experimenters reared out the larval wasps from these nests, they were a species that had never been described before. The barricade of dead ant bodies radically reduced the rate of parasitism. Less than 3% of brood cells of these wasps were parasitized, compared to 16.5% parasitism for similar species collected in the same area.

Why entomb bodies of ants? "Anting" is a well known behavior for several animals, including many bird species. It's thought the defensive chemicals of ants act as a repellant to parasites and predators. You aren't wearing the skin of your enemy, you're wearing the smell of your enemy.

Melissa /Flickr

It's not clear whether the smell of the ants acts as a deterrent to parasites by suggesting a predator is present, or as camouflage by hiding the wasp's smell from would-be parasites.

The most common ant used in the wasp's "bone house" was one of the largest and most aggressive in the area. By using big ants, are the wasps playing a numbers game where they have to catch fewer ants to fill their bone house? Or are they counting on the bad reputation of the ant to amplify their own waspish badassery?

Because this species is new to science, we don't know the answer to those questions yet. But naming Deuteragenia ossarium, after graveyard bone-houses seems quite fitting.