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 Scientists said on Wednesday they have identified a new species of
spider wasp in southeastern China with grim conduct unlike any other
creature. It crams the outermost chamber of the nests it builds for
its offspring with piles of dead ants.
The female wasps do not hunt the ants for food, instead using the
carcasses apparently to frighten off nest invaders.
"Most of the ant specimens belong to a big ant species with a
powerful sting. So the female wasp has a certain risk of getting
injured or killed," said Michael Staab, a biologist at the
University of Freiburg in Germany, whose study was published in the
scientific journal PLOS ONE.
Centuries ago, the Aztecs and other Mesoamerican civilizations
erected in their cities massive skull racks displaying stacks of the
severed heads of sacrificial victims as well as sculpted skulls -
monuments certain to inspire dread.
The wasps may be doing something comparable.
"It might work similarly to the skull racks, just not by vision but
by scent. The ant chamber may give the wasp's nest the scent of a
fierce ant colony - and the nest is thus avoided by natural
enemies," Staab said.
The scientists gave the previously unknown species a fittingly
macabre name: Deuteragenia ossarium, or "bone-house wasp," after an
ossuary, a depository for the bones of the dead.
"Our discovery gives a striking example of the fascinating
strategies of offspring protection that have evolved in animals,
particularly in insects," Staab said.
Staab said when he first saw one of the ant-filled chambers, he also
thought of the ancient Great Wall of China, which protected the
Chinese Empire from attacks by enemies just like the ant wall
protects the wasp's offspring from nest invaders.
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Michael Ohl, a biologist and entomologist at the Museum für
Naturkunde in Berlin, added: "We don't know of any similar behavior
in the animal kingdom, where dead bodies of another species are used
to protect the offspring."
The wasps, discovered in subtropical Chinese forests during a forest
diversity study, are black with a brown spot on their wings. Females
are up to six-tenths of an inch long (15 mm). The males are a bit
smaller and have a white spot on their faces.
Adults feed on pollen and nectar. But the females hunt spiders
larger than themselves as food for their offspring, unleashing a
paralyzing sting and then dragging or flying the victim to the nest.
The wasps build nests in hollow, above-ground cavities in forest
vegetation like the empty tunnels of wood-dwelling beetle larvae.
The nest consists of a series of individual cells made by the
females, each containing a single wasp egg deposited on a paralyzed
spider that will serve as food for the larvae.
The outermost chamber that seals off the nest from the outside world
is where the wasps build a special vault packed with the ant
corpses.
(Reporting by Will Dunham; Editing by Tom Brown)
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