Abstract. 1. The workers and queen of the leaf‐cutting ant Atta cephalotes fed on the juice of swollen hyphae (staphylae) produced by their cultivated fungus, but neither obtained sufficient energy from this source for their respiratory needs. The number of staphylae eaten by workers increased with worker size but was not enough to satisfy their energy requirements.2. Larvae fed on whole staphylae and staphylae previously chewed by workers, and obtained sufficient energy from this source for respiration and growth. No evidence of feeding on fungus hyphae or of trophallaxis between worker and larvae was found. Larvae preferred staphylae to hyphae when fed them artificially and they gained more weight on the former.3. Worker ants imbibed plant sap during the preparation of plant material for the fungus garden and the uptake of carbohydrate during this process was sufficient to supply their energy needs for approximately 24 h.4. Staphylae were richer in lipid and carbohydrate, and poorer in protein than ant fungal hyphae.5. The number of staphylae produced by the fungus gardens of two small nests was comparable with the observed consumption rate but would provide only about 4% of the nest's respiratory requirements.6. In the light of these findings, a revised view of the role of the fungus in the diet of the ant is discussed.

Abstract. 1. In laboratory nests the ants thoroughly licked leaf fragments by a rasping action of their glossa before inoculating the food fungus. The extent of this licking varied with the substrate and was influenced by the thickness of surface leaf waxes and by the chemical attractiveness of the substrate. 2. Microscopy and wettability studies showed that licking removes the wax layer present on leaves. It also removes or inhibits micro‐organisms present. 3. Chemically de‐waxed and decontaminated leaves and ant‐licked leaves proved the best substrates for artificially culturing the ant fungus. 4. The process of substrate preparation circumvents some of the normal defence mechanisms of green plants against fungal attack. The ant fungus thus utilizes nutritionally richer resources of green leaves normally available only to specialized parasitic fungi, rather than the nutritionally inferior shed leaves normally available to saprophytic fungi.

Abstract. 1. Laboratory ants preferred eating whole ant fungus staphylae to hyphae, and did not feed on other fungi. Homogenized ant fungus staphylae and hyphae were equally acceptable liquid food but other homogenized fungi were not drunk extensively. 2. Various arthropod fungjvores preferred to feed on ant fungus rather than any other fungus tested. Some preferred hyphae to staphylae, some vice versa and others had no preference. 3. The ants attacked animals on the nest and reduced the numbers of fungivores on the fungus garden. 4. The ant fungus grew best at 24.5°C and hardly at all at 10°C or 37°C. 5. The ants did not necessarily choose material which supported the best fungus growth in sterile culture and readily accepted substrates on which the fungus did not grow at all. No learning behaviour was noted. 6. The ant X fungus symbiosis is discussed as an example of co‐evolution, a product of an evolutionary feedback. The ant is supplied with a highly nutritious, readily acceptable food source in return for complex fungus‐culture behaviour, providing protection from fungivores and competition from other saprophytic fungi.