MULTIPLE STORED VIEWS AND LANDMARK GUIDANCE IN ANTS

Under some circumstances, Diptera and Hymenoptera learn visual shapes retinotopically, so that they only recognize the shape when it is view ed by the same region of retina that was exposed to it during learning (1,2). One use of such retinotopically stored views is in guiding an i nsect's path to a familiar site(3-5). Because the retinal image of an object changes with viewing distance and (sometimes) direction, a sing le stored view may be insufficient to guide an insect from start to go al. Little, however, is known about the number of views that insects s tore. Here we show that wood ants take several 'snapshots' of a famili ar beacon from different vantage points. An ant leaving a newly discov ered food source at the base of a landmark performs a tortuous walk ba ck to its nest during which it periodically turns back and faces the l andmark The ant, on revisiting the familiar landmark, holds the edges of the landmark's image steady at several discrete positions on its re tina. These preferred retinal positions tend to match the positions of landmark edges that the ant captured during its preceding 'learning w alks'.