In social insects, foraging individuals gather food that predominantly supports the rearing of the brood and satises the energetic demands of nonforaging individuals. Thus, the foragers’ activities serve the benet of the colony rather than their personal prot. Food collectors sometimes even “sacrice” their individual performance and gather food at suboptimal rates (Núñez 1982; Roces and Núñez 1993), in exchange for a faster return to the colony and the activation of additional foragers (Roces and Núñez 1993; see also Chapter 14). At the individual level, therefore, social insect foraging does not necessarily t into “simple” concepts, theories, and models of “optimal foraging” (Pyke 1984; Stephens and Krebs 1986) or “social foraging” (Giraldeau and Caraco 2000), which have been developed for vertebrates (or vertebrate groups) that optimize their food-collecting activity in accordance with their individual needs. Yet, the optimality of food exploitation in social insects has to be considered at the level at which natural selection takes place-that is, the entire colony.