Effects of the ant Lasius niger (L.) on insects preying on small populations of Aphis fabae Scop. on bean plants

SUMMARY Small populations of Aphis fabae were wholly or partially protected by the ant Lasius niger which drove most predators away. Predators eliminated whole colonies of unprotected aphids or persistently restricted their numbers. Protection of the aphid against predators is probably more important than hitherto thought, and may be more important than the other ways in which ants affect the multiplication rate of A. fabae.