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The ants divide labour according to age, with
the oldest individuals being trap builders 
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A fierce
species of Amazonian ant has been seen building elaborate traps on
which hapless prey are stretched like medieval torture victims,
before being slowly hacked to pieces.
With cunning and patience, Allomerus decemarticulatus
worker-ants cut hairs from the stem of the plant they inhabit, and
use the tiny fibres to build a spongy snare, Nature magazine
reports.
This ingenious feat of engineering has only ever been observed in
one other species of related ant, French researchers say.
The ants cut hairs to clear a path under the plant stem, while
leaving some hairs standing to form "pillars" on top of which the
lethal platform will sit.
Using the plant hairs they have harvested, the ants weave the
platform itself, which is bound together and strengthened using a
special fungus.
When the ants have completed the chamber they puncture holes all
along its surface, each just big enough to poke their heads through.
Then, hundreds of worker ants climb into the chamber and wait for
an unfortunate victim.
Ancient sacrifice
"Workers will hide inside the platform, with their mandibles just
inside the hole and they will wait there for prey to come,"
co-author Jerome Orivel of the University of Toulouse, France said.
Anything with legs slim enough to fit through the carefully
constructed holes will meet a miserable fate if they are foolish
enough to enter the trap.
There is no limit to the ants' ambition - they
will try to catch any mammoth of the insect
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"They will
catch almost anything that goes on the trap," continued Dr Orivel.
"And they will grab anything they can - legs, antenna, anything."
Once the prey is well secured by jaws fastening all its
extremities, it is stretched over the platform like an ancient
sacrifice to the gods.
Scores of worker ants then stream out from inside the trap and
sting it vigorously to cause paralysis.
Once the creature is dead or fully immobilised, the ants will
carry it to their nest, where they will dismember their prey before
carrying it inside.
"Small insects will be immediately dismembered and transported to
the nest," said Dr Orivel. "But bigger insects will stay on the trap
for up to 12 hours."
There is no limit to the ants' ambition and they will attempt to
catch any mammoth of the insect world - so long as it has slender
legs.
"Their success depends on the type of insect," Dr Orivel told the
BBC News website. "The insects' legs have to be smaller than the
holes otherwise they cannot get hold of them.
"The ants must have something to catch - for example,
caterpillars will have nothing to get hold of so they will not be
preyed upon."
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