Polistes

The founding stage begins in the spring when a solitary female (the "foundress") (or a small group of related females) initiates the construction of a nest. The wasps begin by fashioning a petiole, a short stalk which will connect the new nest to a substrate (often the eave of a house or outbuilding), and building a single brood cell at the end of it. Further cells are added laterally in a hexagonal pattern, each cell surrounded by six others. Although nests can achieve impressive sizes, they almost always maintain a basic shape: petiolated (stellocyttarous), single-combed, unprotected, and open (gymnodomous).

Eggs are laid by the foundress directly into the brood cells and are guarded by the foundress and the assisting females (if present). After the first larvae hatch, the foundress feeds them via progressive provisioning, bringing softened caterpillar flesh to the larvae multiple times throughout their development (as opposed to the one-time provisioning seen in some other hymenopteran groups). Each of this first seasonal brood of new paper wasps is exclusively female and destined to a subordinate worker position inside the nest; they do not found their own nests and instead assist their mother in the care and maintenance of future sisters.

Some foundress wasps do not build their own nests, but rather attempt to usurp that of another female. These usurpation attempts may or may not be successful, but almost always result in impressive displays of aggression and violence. Females may also adopt a more peaceful alternative reproduction strategy by joining the nest of a close relative (usually a sister) and working as assisting females. In the latter case, such cofounding females are generally, but not exclusively, close relatives.[8]

The worker phase usually begins in the early summer, roughly two months after colony initiation, with the emergence of the first workers. These new females take up most of the colony's work duties, foraging, caring for brood, and maintaining the structure of the nest. Around this time, those females which assisted in nest foundation (if present) are driven from the nest by aggressive behavior on the part of the foundress, and leave either to start their own late-season nests or usurp another's.

The reproductive phase of the colony begins when the first female reproductives (the gynes) emerge from their brood cells. These reproductives differ from their worker sisters by having increased levels of fat stores and cryoprotectant carbohydrate compounds (allowing them to survive the overwintering period). These reproductives contribute genes directly to the next generation, while their worker sisters normally pass along their genes indirectly.

Once male reproductives emerge and both males and females disperse from the natal nest for mating flights, the so-called intermediate phase begins. Brood care and foraging behavior decline and worker numbers drop as dying individuals are no longer replaced by new ones. Intracolonial aggression increases and the social cohesion of the nest declines. In temperate Polistes species, individuals (almost exclusively inseminated females) gather in groups of up to 50 individuals and seek a sheltered location (called a hibernaculum) in which to overwinter.

The reproductive behavior of Polistes wasps provided some of the first evidence for the mathematical biologist W. D. Hamilton's 1964 theory of kin selection. Hamilton showed that animals such as workers could be expected to provide assistance to relatives such as their queens according to the costs and benefits involved (K) and their degree of genetic relatedness (r), and gave the rule that now carries his name, K > 1/r.[9] Early caution existed among researchers as to whether social insects could really assess their relatedness. Hamilton himself suggested an alternative possibility, namely that kin could become associated simply by "population viscosity" —that offspring tend not to disperse far from their birthplaces— and West-Eberhard (1969) found some evidence for this in Polistes. However, Polistes species are now known to learn and remember chemical signals (hydrocarbons) picked up from the nest to distinguish nestmates accurately from non-relatives.[10]

Morphologically, the foundress and subordinate reproductive members of the colony differ little. However, behavioral differentiation occurs among females both between and within generations. For example, in the species Polistes humilis the queen displays a "tail-wagging" behavior to assert her dominance over the worker class.[11] Similarly, Polistes canadensis also possesses behavioral differentiation between the queen and her nestmates, with the queen often suppressing the aggressive behavior of subordinates through lateral abdominal vibrations and stroking. In contrast, unmated females are not aggressive.[12] In Polistes exclamans queens have different amounts of glucose, fructose, and trehalose which lead to different cryoprotectant levels. This alters their survivability in different temperatures, increasing their odds of reproduction. Females in P. bellicosus are also morphologically similar between caste separations. For example, a P. bellicosus worker could become queen, and egg-layer, if all of the original foundresses die or leave the nest.[13] This is also true for Polistes dorsalis, which also displays dominant behavior. Despite having no distinct morphological caste, roles of P. dorsalis tend to be fixed in a system with division of labor.[14]

Polistes spp. discriminate colony mates using an acquired (i.e. learned) cue, absorbing hydrocarbons from the natal nest at eclosion.[15] This cuticular hydrocarbon "signature" is derived both from the plant material and the foundress-applied substances from which the nest is made. Studies of Polistes fuscatus have researched the molecular basis of the recognition "pheromone" used by the wasps, and indicate at least some of the recognizable labels have the same chemical constituents as the adult cuticular hydrocarbons. Similar recognition is found in Polistes metricus.

Dominant individuals of P. dominula have differing cuticular profiles from workers,[16] and the frequent observations of the dominant female stroking its gaster across the nest surface, combined with its staying on the nest for longer times than subordinates, suggests the dominant individual may contribute more to the nest odor.

P. carolina females do not preferentially feed their own progeny (as larvae),[17] so it may be the case that nest odor only serves as a likely indicator of relatedness, rather than a specific label of kinship.

Further to this recognition of nestmates, Polistes biglumis foundresses discriminate between 'alien' eggs and their own via differential oophagy.[18] The mechanism of differentiation is not elucidated, but is thought to be based upon differences in cuticular hydrocarbon odor.