Guinea Paper Wasp

Appearance

Paper wasps' size can range between 3/4–1 inch in length. "Polistes bodies are slender and narrow waisted. Most "P. exclamans" have a yellow spot on the lower mesopleuron. Most metasomal segments have yellow apical fasciae and the propodeum has four yellow stripes.

They have smoky black wings that are folded lengthwise when the wasp is at rest. "Polistes exclamans" is generally brown and has yellow markings on its head, thorax and abdomen. "Polistes exclamans" have antennae banded with red, black and yellow while most paper wasps only have one antennae color. In females the fore wing length can range from 13.0-16.5mm and in males the fore wings can range from 12.0-15.0mm.

The extent of ferruginous markings is variable.

Naming

This species does not have a widely used common name, though in Texas some call it a yellowjacket. A name it shares there with Vespula. The name guinea wasp has been used, but has not been widely adopted. "Polistes exclamans" is also referred to by a generic name for the genus "Polistes" which is called paper wasps.

Behavior

Their colonies contain three castes: workers, queens and males, though differences between workers and queens are generally plastic and behavioral. The physiological similarities between the worker and queen castes have led to experiments attempting to distinguish the characteristics of these two castes and how they are determined.

"P. exclamans" lives in a hierarchical society with one queen that lays the eggs. However, all of the females have the same morphology and they all have the physiological capability of taking over the egg laying if necessary eg. queen death, queen migration.

Since the queen has the same morphology as the rest of the workers in the colony, this raises the question as to how the queen is determined and what makes her special. Studies have found that queens and males have higher levels of glucose, fructose and trehalose than workers, leading to higher cryoprotectant levels; "P. exclamans" use these sugars as cryoprotectant.

They work by increasing the solute concentration in cells. This results in a greater survivability in colder weather. It was found that queens have a 76% survival rate in 5°C weather compared to 17% survival of the workers over a 15 day test period. The queens also have a 0.5mm layer of fat surrounding their bodies; this allows them to live longer into the winter and possibly extend their mating season. The queens seem to be the only ones capable of diapause.

Habitat

"Polistes" nests can be built from wood fiber which are collected from posts and plant stems. The fiber is formed into a paper like comb with hexagonal cells. The nests are orientated downward and are held up by one filament. "P. exclamans" have also been observed occupying artificial nests put out by researchers and consisting of bundles of straws.

Reproduction

As with many other insects, "P. exclamans" use sexual pheromones to attract members of the opposite sex. Researchers attempted to determine the role of sexual pheromones in sexual attraction in paper wasps. They set up a wind tunnel where males and females were exposed to a sexual pheromone wick that was isolated from males and females. These pheromones were taken by hexane extracts from wholes bodies and thoraces of unmated females. The male extracts were taken from the ectal mandibular and seventh sternal glands. It was found that the opposite sex was attracted upwind of the scent and the results were intensified when a fan was turned on to intensify the pheromone. The range of the scent was found to be around 2 metres.

In nature, it was observed that males would venture away from the nest in order to attract females. The males would press their gastral sterna against a perch and rub their mandibular against it. This is used to attract females, and females were observed to visit these branches and sample the scents. Interestingly, it was also found that on some occasions, males were attracted to other male scents.Satellite nests are common among "P. exclamans." A queen will fly somewhere between 0.15 to 11m away from the original nest to settle in a new location. About 16–39% of nests create satellites from May to July. The satellites are used as an insurance against attacks by predators and parasitoids. Of 12 nests that were knocked down by birds that had satellites, 66.7% of the colony survived by moving to the satellite, compared to the reproductive success of nests with no satellite that were attacked. When "Chalcoela iphitalis" invaded, the prevalence of satellites didn’t increase the survivability, however it did have an effect when "Elasmus polistis" were introduced; it gave the "P. exclamans" a place to escape to.

Workers who are older typically start satellite nests and have more developed ovaries; younger and lesser-developed workers join the satellite after its establishment. The distribution of workers between the main nest and satellite is very important because they are needed for the establishment of the satellite and for the continued running of the main nest; although, after several months the main nest can become abandoned. If not enough workers follow the initial worker to the new nest, then it will most likely fail as a satellite.

Predators

A typical "P. exclamans" worker will live somewhere between 14–16 days. The oldest wasp to be observed in a natural colony was 102 days old. Queens typically live 6 times longer than the workers. There has been some variation observed with the life expectancy of "P. exclamans". This has typically been attributed to the colony of origin. It also must be noted that while there is variation between colonies, there typically is less variation between the original nest and the satellite nest.

Variation inside a single colony may also occur because of the presence of different castes. Foragers, those who frequently travel outside the nest, lead a riskier life and tend to have lower life expectancy than those who stay in the nest. Though, it was observed that colonies with high foraging rates also had higher reproductive rates to compensate for the lower life expectancy. Another interesting aspect that was observed in one nest was that an increase in female population led to lower longevity. This was because the females were more focused on competing to become the next queen than foraging and fulfilling their roles.

Worker death is an important factor in colony failure, and it is in fact the cause of 13–76% of colony failures. This may be in part due to the small colony size; because the colonies are small, worker longevity is crucial for the survival of the nest.

Defense

"Polistes exclamans" are also interesting in their behavior and ecology. The high worker and queen mortality rate has led to the prevalence of satellite nests. The high queen mortality has also resulted in interesting responses by the worker caste. The high mortality is mainly caused by parasitoids and predation. "P. exclamans" have developed defense mechanisms to reduce the rate of colony extinction as a result of this predation and parasitism.