Polistes fuscatus

P. fuscatus has a linear dominance hierarchy that revolves around the fertility of each individual wasp; those that are more dominant within the nest generally have the larger or more developed ovaries.[10] The hierarchy is first formed in the pre-emergence period between foundresses in which they fight aggressively to establish dominance until the hierarchy is established, and only later formed among the workers of the colony such that they are integrated into the hierarchy.[10] When the queen is removed, the second highest ranking female then takes the queen place in being the primary egg layer.[10]

The posture of wasps is very telling of which is dominant or subordinate. The dominant wasp generally sits higher than the subordinate, whereas the subordinates have a lower stance.[10] For wasps of equal rank, it is not uncommon for them to continuously try to rise higher and begin to aggressively fight each other until they fall due to losing their foothold.[10] This is often called the falling fight, though it is more common for one wasp to act as a subordinate.[10]

Dominance ranking may also affect the location females may be at within the nest and how far away wasps are spaced. In P. fuscatus, those who are higher on the dominance ranking make continuous darts at other lower-ranking wasps such that other wasps will not closely sit near the higher ranking wasp.[10]

Members of a colony are able to recognize non-resident wasps by how they approach the nest and by their dominance behavior.[10] Members of the colony approach the nest in a swift and purposeful fashion, whereas wasps that are not part of the colony hover by the nest and do not exhibit a specific direction.[10] Oftentimes, they hover by the nest without landing. If spotted, members of the colony begin to act aggressively and alarm others of the possible intruder.[10] Non-resident wasps are often chased out of the nest within the first five minutes of entering.[10]

On occasion, however, resident wasps may mistake other resident wasps as non-resident wasps.[10] This occurs when the mistaken wasp has just come back from foraging and is too full to obtain the velocity necessary to fly towards the nest as if it were a resident of the nest. Sometimes, to obtain the speed necessary, the wasp attempts to approach the nest several times.[10] Dominance relations also allow for members to recognize nest mates as each wasp is of a particular rank; when a non-resident arrives and has no dominance rank, it is conceived as being unfamiliar. Wasps that are not part of the colony are only accepted without aggression when a dominance hierarchy or conflict has not occurred.[8][10]

Individual recognition is highly important in the formation of behavioral interactions between members of different castes within a population of P. fuscatus.[8] The ability to recognize individuals is vital for the existence of a linear dominance hierarchy, in which is a determinant for many aspects of behavior of the paper wasp, including the amount of food and work an individual wasp would be able to have or need to accomplish, the amount of aggression one may receive, and the number of offspring a specific wasp may produce.[8] The ability to recognize individuals also helps dictate how one wasp may treat another, whether it be to hold a dominant role or to act submissively within an interaction.[8]

P. fuscatus has the capability to not only recognize where wasps of their population may fall in the hierarchy, but may also be able to recognize individual nest-mates through specific facial and abdominal markings.[8] One study indicated that if the facial and abdominal markings of a wasp were to be changed through painting with different color paints, mainly black or yellow, when the wasp was reintroduced into the nest, it would receive much aggression until it was reaccepted back into the colony (i.e. when the nest-mates felt familiar with that wasp).[8] The study was able to indicate that recognition was specific to the individual given that there was no relationship between specific markings and dominance rank, rather markings were purely used for individual recognition.[8] Furthermore, previous research by Bura and Gamboa indicated that wasps use chemical cues to identify nest-mates and wasps that are foreign to the nest would be immediately chased away within the first five minutes. That the reintroduced wasps were not chased away is a strong indication that facial and abdominal patterns are not used for net-mate recognition, but is only used for individual recognition.[8]

The ability to recognize individuals may not only be useful for behavioral interaction, but may also be used to reduce aggressive interaction between individuals of different dominance ranks, as well as to help foundresses determine and regulate the amount of resources each individual within the nest receives.[8]

A greater part in the division of labor in colony defense is given to the queen of the colony.[21] Queens come into contact and interact with non-resident wasps and returning nest-mates more compared to other resident wasps and are the first to come into contact with the wasp intruders at a much higher rate. Although this finding could be attributed to the queen's location preference of being at the face of the nest, it was found that even normalizing for the preferred location, queens still encountered non-nest mates at a higher rate than expected.[21] In addition, queen wasps are much less tolerant of non-resident and returning nest mates compared to non-queen nest mates; however, both the queen and the colony members become less tolerant of non-resident wasps later on during the colony cycle.[21]

Queens may be less tolerant of intruders compared to other colony members due to the consequences of accepting non-nest mates into the colony.[21] Often, female intruders that join the colony attempt to evict the previous queen and usurp the position. Whereas this result is harmful for the queen, other members of the nest are not negatively impacted; they would simply remain in the nest and serve the new queen.[21] Therefore, much of the defense of the colony is left up to the queen.[21]

P. fuscatus invests much in the nests.[16] Nests provide locations that members of the colony can return to and act as a central location that can allow for more efficient work in reproduction and foraging behavior.[16] Although nests can provide many benefits, it also has the disadvantage of concentrating all investment in one area; this concentration allows for vertebrate predators to have the ability to destroy an entire nest and therefore destroy all investment. Vertebrate predators of P. fuscatus include foxes, rodents, and birds.[16] Judd's study on the defensive behavior of colonies of the paper wasp indicated that the behavior of wasps was highly dependent on reproductive investment.[16] Prior to the emergence of many adult wasps, the wasps acted much more aggressively; however, when the nest no longer contained any brood and, therefore, not much investment, the wasps were much more likely to flee instead of act aggressively against the vertebrate predator.[16]

Foraging for fibres

Edwards indicated in his work that social wasps, “collect water, plant fibers, and carbohydrates, and hunt arthropod prey or scavenge animal proteins.” [22] Water is used for the following processes: nest cooling, construction, and metabolism; plant fibers are used for construction, and carbohydrates and protein is used as food and energy.[5] Water is a vital resource for wasps given its many capabilities, and many wasps will go to a variety of places to obtain it, such as puddles and ponds, or even drinking fountains and faucets.[5] Wasps are able to obtain water by imbibing it and regurgitating it once they return to the nest and are able to use it for construction by mixing it with the masticated plant fibers.[5] These plant fibers are collected from dead wood. By mixing the plant fibers with water, wasps are able to create pulp which is then used to help the construction of nests.[5]

P. fuscatus is considered to be a generalist prey forager, but may also act as a specialist due to its habit of commonly returning to a specific location or to prey on the same species.[5] They use the scavenged animal protein from both vertebrates and arthropods such as: caterpillars, flies, alate ants, termites, spiders, bees, and other wasps to help the development of their brood.[5] Social wasps collect carbohydrates from nectar, sap, and fruits and may store them within the nest; some wasps may even steal or consume carbohydrates from other carbohydrate foraging or making arthropods.[5] Although the foraging of social wasps is not as developed as some other arthropod species given its weakness in recruitment, the ability to communicate to nest mates of the location of a resource stronghold, it may impact the greater ecosystem.[5]

P. fuscatus eats arthropod prey, animal proteins, carbohydrates and protein. They will eat caterpillars, flies, ants, termites, spiders, bees, and other wasps. Carbohydrates may include nectar, sap, and fruits.[5]

Egg laying by subordinate females and the oophagy of these eggs by dominant female wasps will occur until two weeks after the first female eggs emerge.[10] Prior to these two weeks, egg layers will continuously eat other female wasps’ eggs approximately eleven minutes post being laid; however, no egg layers would ever eat their own eggs, indicating that they could recognize their own individual eggs.[10] It can be conjectured that subordinate egg layers could not lay eggs as quickly as dominant egg layers given the dominant egg layers’ greater supply of ova from the subordinate egg layers indicating that oophagy and oviposition occur close together.[10] Previous studies have also shown that subordinate egg layers may no longer lay eggs after associating with the higher-ranking females after a certain period; this is probably due to the necessity of expending energy during foraging and inability to invest as much into their own eggs.[10]

Prior to hibernation, males and females will undergo mating; they will aggregate together in sunlit areas that are relatively higher in location.[10] Males will sit out waiting to pursue females in order to mate.[10] Once a female is spotted, unlike the usual passive male within the nest, the sexually responsive male will attempt to mount the female and begin performing abdominal stroking. Females will react aggressively in order to struggle free.[10] If the female were to elude the male's hold, the male wasp would return to its position to attempt to copulate again. While copulating, the male exhibits several movements, such as abdominal stroking, extrusion of genitals, grasping the female abdomen, rhythmic antennal vibrations, and grasping of the female antennae.[10] Antennas and antennal movement are important for copulation. Some studies have indicated that females without antenna and females who do not depress their antennae cannot copulate. It has also been proposed that antennal movements help copulation through assisting the attachment of genitals.[10] In addition, research by Post and Jeanne has shown that Polistes fuscatus females have no preference on mating with related or unrelated males.[23]

The mating season for Polistes fuscatus is during the spring and summer, after the nest has been abandoned. Venom is released by females that contains a sex pheromone that induces copulatory behavior in males. The continual release of the venom causes males to try to copulate with females when they are unreceptive on the nest, thus interrupting the activities of the colony.[24] After mating has occurred, the queen will lay an initial generation of infertile female workers. Later on in the life of the nest, male and fertile female offspring are produced.

The eggs capable of becoming queens are laid during the summer. Laying these eggs during the summer ensures that the larvae are well-fed due to the great environmental conditions and abundance of food. These eggs hatch before fall and the resulting offspring hibernate during fall and winter.[18] The new queens or co-foundresses emerge in the spring to begin new nests and lay eggs. After laying eggs that will later develop into new queens, the old queens die along with all accompanying workers and males. As opposed to other eusocial insects such as vespid wasps, Polistes fuscatus have not been found to preferentially mate with their siblings or have sibling recognition mechanisms to aid in kin selection during reproduction.[25] This is surprising since there are many advantages of inbreeding for haplodiploid organisms.[25]

According to Fisher's theory of sex ratio selection, when competition for mates is population wide, parents will evolve to invest equally in both sexes.[19] However, in eusocial hierarchies, there is often conflict between the workers and the queen to promote their genes within the colony. The Queens favors a 1:1 sex ratio, but the workers favor female progeny because they share approximately 75% (r=0.75) of their genes with their sisters, provided that the queen only mated once.[26] In Polistes fuscatus, the sex ratio is usually 1:1 for several reasons. First, males generally leave the nest to scout for mates soon after they reach adulthood, promoting population competition for mates. Second, the number of workers within a colony is relatively small (generally less than 40) making it less likely for a worker to confront the queen. Also, since colonies are annual and workers are reared by the queen's subordinate foundresses, the queen can manipulate how much food they receive as larvae. Polistes fuscatus queens likely mate with multiple males so that the relatedness of workers is less than if they all shared the same father's genes. Finally, in the second generation of the queens offspring, males are usually reared earlier than reproductive females. Thus when the workers have the opportunity to bias the sex ratio, there are few male larvae present. Additionally, the males have usually completed part of their development, giving them a higher reproductive value than new eggs. Thus the costs of destroying male larvae or replacing the male larvae with their own eggs is not worth the investment.[19]