The amount of prey brought into the nest attains a maximum in May, which in the years of an outbreak of Tortrix viridana is not much higher than during the times of latency of this insect, and depends at least partly on weather in summer. The crop volume of foraging ants reaches maxima in spring and late summer, probably depending on the abundance of the main producer of honey-dew, Lachnus roboris L. The sugar concentration of crop fluid fluctuates around a mean of 0.25 g/cm3 in summer and decreases in autumn. The nitrogen concentration attains maxima in spring and autumn, corresponding to maxima of nitrogen concentration in honey-dew. Moreover, the quantity of arthropod nitrogen in the crop increases in spring.The larger amount of prey brought into the nest during the occurrence of Tortrix viridana does not affect the number of ants running out, the number of ants climbing trees, the ranges of activity of the nest populations as well as the quantity of honey-dew collected. Apparently ants are capable of regulating to a certain extent the quantity of honey-dew and the amount of prey collected in spring. Furthermore, they select the different sources of honey-dew or prey according to abundance and productivity of the latter. They do not become specialized exploiters of the most productive source of food.