Eusociality Formica polyctena like many
ant,
wasp and
bee species, displays a
eusocial system. Eusocial insects are characterized by cooperative care of young among members of a colony, distinct caste systems where some individuals breed and most individuals are sterile helpers, and overlapping generations so mother, adult offspring and immature offspring are all living at the same time. In a eusocial colony, an individual is assigned a specialized caste before they become reproductively mature, which makes them behaviorally distinct from other castes. Red wood ants exhibit all of these characteristics, with queens and males that make up the reproductive caste and sterile female workers that aid in brood care and colony maintenance.
Worker sterility Workers in ant colonies are typically sterile females that do not reproduce.
F. polyctena is consistent with this model, with almost completely sterile workers that do not lay eggs. This is in contrast to other
Formica species that have workers that actually do reproduce, disrupting the eusocial system. ''F. polyctena's'' high proportion of worker sterility indicates a strict obligate polygynous colony structure that most likely allows for a stable unicoloniality, or the cooperation of several nests. In other words, workers do not have the ability to disrupt the strict social segregation of reproduction by reproducing themselves. Thus they uphold a multi-queen, multi-nest cooperation that may not be advantageous to their genes since they act altruistically toward non-kin.
Foragers In
F. polyctena colonies, there appears to be a separate group of designated foraging workers. The number of foragers correlates with the size of the colony. Foragers also tend to be older workers. However, if foragers are lost or die, other workers from the nest can replace them, indicating some flexibility in designated roles within the colony. These replacement workers have a shorter life expectancy as foragers, indicating that there could be some physiological development as the workers age that allows them to be effective foragers.
Nestmate recognition In order to prevent costly conflict between fellow nestmates or involuntarily altruistic behavior toward ants from a foreign nest, individual ants need to distinguish between their fellow nestmates and foreigners. It has been demonstrated that
Formica polyctena uses genetically-based cues as a nestmate recognition mechanism. Since
F. polyctena, like all ant species, lives in colonies with high genetic relatedness, this type of mechanism would be successful in distinguishing between colonies. Beye, Neumann and Moritz conducted a study where pairs of ants from different nests were introduced to each other to see if they fought, tolerated or avoided one another. Pairs of ants from the same nests were introduced as well to act as a control. Genetic similarity between these ants was measured as well. A strong positive correlation existed between antagonistic behavior and genetic dissimilarity. Thus,
F. polyctena ants mostly likely recognize their fellow workers through some genetically produced signal. Nest populations in close physical proximity to one another did not necessarily demonstrate either extremely aggressive or passive behavior toward each other, indicating that nest proximity does not influence recognition. Additionally, nest distance did not correlate with genetic similarity. Essentially,
F. polyctena has adapted some form of genetically-based cue that allows nestmates to distinguish between each other and foreign individuals. Beye, Neumann and Moritz believe that these genetic cues act to keep nest colonies separate in homogenous environments that offer no other nestmate recognition strategies.
Alarm signals Alarm behavior can be triggered in
Formica polyctena by the release of pheromones. When ants come across a specific pheromone, they approach the source with jaws wide open, as if confronting a threat. Specifically in
F. polyctena, these chemical alarm signals elicit a response not only within the nest, but along foraging paths. In particular, the formic acid sprayed by ants when attacked can trigger a predator alarm response in nearby ants, gathering reinforcements to attack the predator. In this way, formic acid doubles as a chemical weapon against predators and an alarm signal in
F. polyctena.
Disease resistance Due to the close living situation of individuals in a
F. polyctena colony, diseases can spread rapidly, causing significant damage to the colony's population. Therefore,
F. polyctena has evolved responses to combat the spread of disease. When an individual ant develops an immune response to some disease, the other workers can sense this. The workers decrease mouth-to-mouth exchanges of liquid, and prevent the infected individual from moving around. The healthy workers also increase antennal contact and grooming of the infected ant. This is believed to either remove pathogens from the ant that could cause such an immune response, or act as a "social vaccination". Aubert and Richard proposed this social vaccination model, where they argue that if fellow nestmates groom an infected ant, they will be exposed to small amounts of the pathogens or molecules that could trigger an immune response within the healthy individuals. In essence, the healthy individuals develop a resistance to the pathogens carried by the infected individual before the pathogens can spread and infect them.
Wars and cannibalism F. polyctena colonies wage wars on neighboring colonies. During wars, any dead ants are cannibalized by the colonies. These wars occur when food is scarce, usually during the spring months, so that the colonies can effectively feed a new generation of ants. Old workers commonly participate in these wars, due to their lower life expectancy than young workers. Spring wars allow the colonies to produce new generations consisting mainly of reproductives (queens and males) rather than workers. The rare wars during the summer and fall months produce food for new generations of workers instead. These young workers are more likely to survive the winter than the old workers who die in the wars. Essentially, the colonies recycle their food resources in the form of workers. Old workers die and are eaten to give rise to either reproductive or new workers. Even if a colony "loses" a war and there is a net loss of workers, the warring still provides food, and thus is beneficial to the colony. However, cannibalism is not an efficient food source unless other food resources are scarce, since one new individual requires more food input than another individual's body can provide.
Larvae predation Haccou and Hemerik studied the effects of the
cinnabar moth larvae (
Tyria jacobaeae) distribution on predation by
F. polyctena. They found that the ants preyed more on larvae when they were on the ground than on plants. The ants also preyed more often on larvae that were concentrated in clusters over ones that were evenly dispersed. This is most likely due to communication between the ants, where when one worker discovers food such as a group of larvae, she alerts fellow workers. ==Nest temperature regulation==