Following what I did read , observed myself in wild colony and artificial nest it seems that Tetramorium caespitum biggest food intake come from small seeds (dandelion , clover , heat , grass... ) .The animal food is constitute of slow moving preys: diverse insects larvae ( caterpillars, maggots , beetle larvae ...) of every sizes and earthworms and carrion of not only insects but a dead lizard , mouse or bird when the occasion occurred. They keep aphids on plant roots only but it seems to be a less important part of their diet. They use foraging gallery's and tracks (mostly covered) and forage far on the ground and underground without climbing on the vegetation , they like the heat but do not like to forage in full sun . Tetramorium does not hunt large fast moving prey except if they constitute a danger or a competitor.
The number of workers in the smallest colony is now several hundreds (I can't count any more) and growing fast .The food intake is now equivalent of two tenebrions pupae +sun flower seed + many dandelions seeds.
The population of the biggest colony is now a few thousands (impossible to count) eating the equivalent of 5 or 6 tenebrion pupae , 8 sun flower seeds and a large quantity of dandelion seeds every day.