With the spread of angiosperms some lineages of ants, originally ground-dwellers and predators, adapted to arboreal life. Ground-nesting worker ants probably constituted the first case of biotic plant protection through their predatory activity while foraging on plant foliage. Then, ants developed tight evolutionary bonds with plants varying from facultative diffuse relationships to obligatory specific associations, necessary to the survival of both partners. In diffuse relationships plants induce different ant species to patrol their foliage by producing energy-rich food rewards such as extra-floral nectar (EFN) and/or food bodies (FBs) (Dejean et al. 2007, Heil 2008, Heil & McKey 2003). First described by Janzen (1966), myrmecophytes, or plants that provide specialized plant-ants a nesting place in hollow structures called domatia, represent a good example of a strict association as, in return, they are protected from several kinds of enemies, particularly defoliating insects (Heil & McKey 2003, Hölldobler & Wilson 1990).
