The polyphagous drywood termite Kalotermes flavicollis (Fabricius) can establish its colonies inside living trees, causing a progressive debilitation that ends with the death of the plant. For this reason, it is considered one of the major pests of Sherry vineyards in Andalusia, SW Spain. To analyze the trends of colonization of this termite, a detailed investigation was performed during 16 mo in seven districts of the Sherry area, cutting randomly selected grapevine trunks into six sections, from which all individuals were collected and counted according to their developmental instar or caste. The results detected variations in the social composition of the groups colonizing grapevines according to the spatial distribution inside the vine trunk and in the numerical trends over the seasons. A pattern of seasonal migrations of the termites inside the trunk was inferred, with upward movements from spring to autumn and downward movements from autumn to winter. During winter, when termites were mainly located in the medium-basal sections of the trunk, a higher proportion of eggs and larvae was detected. Going from spring to summer, when the majority of the termites was located in the medium-upper sections of the trunk, there was an increase of nymphal instars followed, during autumn, by the appearance of alates, mostly located in the upper sections of the grapevine. Pseudergates and reproductives maintained their proportions and locations almost unchanged during the year.