Colony success of the submissive ant Formica fusca within territories of the dominant Formica polyctena

Abstract. 1. Twenty-three nests of the submissive ant Formica fusca L. were sampled in two adjacent territories of the dominant wood ant Formica polyctena Först. The nests were dug up at different distances from the wood-ant mounds. Distance is assumed to be inversely related to the extent of disturbance of F. fusca by F. polyctena.
2. Colony success of F. fusca was assayed by counting the numbers of workers (colony size), and worker and sexual offspring in a nest. For individual size, the head width and dry weight of fifty workers per nest were measured.
3. Colony size correlated positively with the numbers of worker and sexual offspring in one territory, but only with worker offspring in the other.
4. Distance from the wood-ant mound correlated positively with colony size and numbers of worker and female offspring in one territory. In the other territory distance correlated positively with number of females, but negatively with number of worker offspring. No significant correlations between distance and the size measurements were obtained.
5. Because of its nonaggressive behaviour F. fusca may nest fairly close to a wood-ant mound but is likely to show reduced abundances in terms of nest density and forager number, and, ultimately, lowered fitness.