Nightmarish 'supersoldier' ants with huge heads and jaws have been created by activating ancient genes.
Scientists believe the monster ants may be a genetic throwback to an ancestor that lived millions of years ago.
Scientists say they can create the supersoldiers at will by dabbing normal ant larvae with a special hormone - the larvae then develop into supersoldiers rather than normal soldier or worker ants.
Supersoldier ants can occur naturally in the wild, but only rarely. In the deserts of America and Mexico, their job is to protect the colony from raids by invading army ants.
The supersoldiers use their enormous heads to block the nest entrance and attack any enemy ants that get too close.
Scientists showed that ordinary ants of the species Pheidole morrisi contain all the genetic 'tools' needed to turn them into supersoldiers - they just need a hormonal push.
The research is reported today in the journal Science.
Authors Dr Rajendhran Rajakumar, from McGill University, Canada, and colleagues wrote: 'We uncovered an ancestral development potential to produce a novel supersoldier subcaste that has been retained throughout a hyperdiverse ant genus that evolved 35 to 60 million years ago.'
The results suggest that holding on to ancestral development toolkits may play an important role in evolving new physical traits, say the researchers.