Leaf-cutting ants and avoided plants: Defences against Atta texana attack.

Leaf-cutting ants (Formicidae; Attini) characteristically never attack some common plant species in their habitats. These plants may be defended against the ants in several ways. In Texas, mature leaves of Sapindus saponaria (Sapindaceae) and Celtis reticulata (Ulmaceae) are unpalatable to Atta texana Buckley foragers, while mature leaves of Berberis trifoliata (Berberidaceae) are palatable to the ants, but are too tough to cut. Young Celtis leaves and and young Berberis leaves are palatable and can be cut by the ants, however. These young leaves may escape attack by remaining palatable a brief amount of time (new Celtis leaves), or by occurring patchily in space and time (new Berberis leaves).