The pollen present in food reserves, pollen masses and honey, stored in an aerial nest ofBombus atratuswas investigated. Field observations were also made. 23 pollen morphological types, belonging to 16 families of plants, were identified. The principal sources of nectar were:Eucalyptusspp.,Aptenia cordifolia, Lagerstroemia indicaandSalvia microphylla.WhileSolariumspp. and Liliaceae, were the main sources of pollen. These analyses of pollen reserves and honey, coupled with field observations, allow a reconstruction of the wide foraging spectrum ofBombus atratus.