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Sex allocation
Formica exsecta is a eusocial species, displaying a dominance hierarchy among its individual colony members. Amongst the narrow-headed ant species, there are two different types of colony structure: monogyny, one queen per colony, and polygyny, more than one queen per colony. Usually, one of these two types is prevalent within a population. These two types of colonies differ not only in the queen’s mating system, but also in the organization of types of offspring and hierarchy system. In order for a polygynous colony to thrive, it must vary its sex allocation practices depending on the abundance of resources. Colonies produce a greater percentage of male offspring when there is restraint on resource availability, as well as when the colony has a larger number of queens. The opposite scenario is also found to be true. More female offspring are produced when there is an abundance of resources, as well as when the colony has a smaller number of queens. On average, a colony’s sex ratio is estimated to be 5.8% female, or one female for every 17.2 male offspring. This heavily male offspring based sex ratio displays an obvious deviation from Fisher’s theory of 1:1 sex ratio.

Colonies in which the male offspring are favored, workers tend to execute most of the female gynes. In contrast, colonies where an excess of female gynes is produced, which is more than necessary for the simple act of queen replacement, they are all accepted into the colony in order to eliminate the possibility of parasitism by unrelated queens from neighboring populations.

Inbreeding
In monogynous colonies, there is found to be a significant amount of inbreeding. Inbreeding coefficients were found positive for the workers of these colonies. No inbreeding was found between mother queens. Procreation between related individuals of the colony can be further explained by the queen-male relatedness coefficient of 0.23, found by experiments from Liselotte Sundström. Male offspring that were reared in an inbred colony tended to be smaller in weight. Gynes reared in inbred colony display no difference in weight compared to those in non-inbred colonies. This result reflects a trade-off between the quantity of offspring and their reproductive quality. Gynes’ reproductive success is more dependant on their weight than that of a male.

Haplodiploidy
Formica exsecta, much like other insects in the order Hymenoptera, have a haplodiploid sex determination system. An unusual 0.75 relatedness coefficient between full haplodiploid sisters is one of the main contributors to the frequency of evolution of eusocial species. The queen’s eggs that are fertilized grow into diploid daughters, which contain two pairs of chromosomes, whereas unfertilized eggs produce haploid males, which only contain the queen's chromosomes. The voluntary fertilization of eggs is done by the egg-laying mother. Therefore, it is ideally in the queen’s best reproductive interest to lay more eggs or increase the number of eggs that produce individual that can reproduce themselves. However, further research showed that female-rich colonies emphasized the production of workers rather than gynes.