Ants can form large nest complexes with thousands of nests, such as Lasius niger for the suburbanized areas of Ukraine. L. niger inhabits meadows, abandoned fields, pastures, and young plantations of coniferous trees. The question of what constitutes the basis of the carbohydrate diet of L. niger ants in such large nest complexes remains unclear. In 2017-2018, 38 plant species were identified in the territory of the L. niger nest complex (Kyiv region, Ukraine). 4 species of plants (Cirsium arvense, C. setosum, Onopordium acanthium, Oenothera rubricaulis) were visited by L. niger foragers in 70–95% of cases. On these species of plants, colonies of aphids acted as sources of carbohydrate for ants. A total of 43 species of aphids were found, of which 32 were localized on the aerial parts of plants, the remaining species - on the roots and root neck of the plants. L. niger monopolize 98% of carbohydrate baits in the territory of the nest complex. A large number of myrmecophilous aphid species promotes effective trophobiosis of L. niger in the territory of the nest complex. This favors the stability of the supply of the carbohydrate resource to the ant colonies inhabiting the nest complex. The existence of the L. niger nest complex is possible in herbaceous plant communities when this ant species is capable of mutualistic relationships with a large number of myrmecophilous aphid species.