William Foster of the Universityof Cambridge in Massachusetts, US, Witnessed a duel between horned aphids (Astegopteryx minuta), which is the first case of a fight over territory to be observed among insects. The difficulry in finding good feeding sites led to the strife. Their weapons were their horns - protrusions on their heads, used as levers to prise the enemy from the prized land. Foster found that the removal of the enemy was followed by the surrounding area getting demarcated With a tiny raised collar of plant tissue, with a diameter of 50 micrometres (New Scientist, V 01150, No 2026).