Tuesday January 9 9:16 PM ET
'Dracula Ants' May Be Key Evolutionary Link

SAN FRANCISCO (Reuters) - A colony of cannibalistic ants discovered in
Madagascar represent an important piece of the puzzle in understanding the
evolution and behavior of one of the most successful insect species in the
world, scientists said Tuesday.

The fearsome-looking insects, dubbed ``Dracula ants'' by their discoverers
because they suck nourishment from their own larvae, are believed to be a
transitional species bridging the gap between ants and the wasps from which
they evolved millions of years ago.

``A living organism cannot be a true missing link,'' said Brian Fisher of the
California Academy of Sciences, who found the ant colony hidden in a rotten
log about 55 miles outside of the capital Antananarivo.

``But this represents our best hope for understanding what the common
ancestor was, which has been a huge impediment for understanding ant
evolution.''

While ants make up only about one percent of all described insect species,
they are among the most widely spread and numerically dominant on Earth --
and researchers want to understand the evolutionary secret to their
success.

Madagascar, an island off southeastern Africa, is regarded as a treasure trove
of biological information because its relative isolation allowed older, or
``relic'', species to survive without competition from newer arrivals.

While the genus of the ``Dracula'' species was first identified in Madagascar
in 1993, Fisher's discovery of the first entire colony of the insects allows
scientists to draw a more detailed picture of ant evolution.

The Madagascar ants, belonging to the genus Adetomyrma, have just a single
connection between their thorax and their abdomen instead of the two or
three joints found in ``modern'' ant species, Fisher said.

``They have got this wasp waist, if you will,'' he said, adding that the single
joint was a clear indication of the ants' link to earlier wasps.

The Adetomyrma ants also display a grisly feeding habit which Fisher
believes may be the basis for the ``social food sharing'' that has come to
characterize ant colonies.

Queen and worker ants, when hungry, visit the colony nursery and cut holes
into their own larvae to feed on the hemolymph, the equivalent of insect
blood.

``They chew them until they bleed,'' Fisher said, explaining his decision to dub
the genus after the vampire Dracula of lore. ``We call this nondestructive
cannibalism.''

Fisher believes that this practice may have evolved into the practice of other
ant species in which worker ants, which are unable to digest solid food
themselves, feed the larvae, which regurgitate part of the digested food back
to the workers for distribution around the colony.

Fisher said further study of the ``Dracula'' colony could provide more clues
on the development of ant behavior -- and could eventually force scientists to
rethink their entire hypothesis of ant evolution.

``This initial discovery told us that our current hypothesis of the evolution of
ants was inaccurate,'' Fisher said. ``It is not just important in that it is a new
species...it is an important piece of the puzzle in the evolution of
life.''

POWRÓT