Polistes exclamans
| Polistes exclamans | |
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| Species: | P. exclamans
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| Polistes exclamans Passerini, 1860
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Polistes exclamans is a social wasp [1] found in the southern United States and northern Mexico. This species has also been observed in Missouri, Maryland, and New Jersey. There has been a northward expansion of the eastern half of the U.S. This expansion is typically attributed to changing global climate and temperatures.[2]
This species does not have a widely used common name, though in Texas some call it a yellowjacket, a name that should be reserved for 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.
Their colonies contain three castes: workers, queens and males, though differences between workers and queens are generally plastic and behavioral[3]. The physiological similarities between the worker and queen castes have lead to experiments attempting to distinguish the characteristics of these two castes and how they are determined.
Polistes exclamans are also interesting in their behavior and ecology. The high worker and queen mortality rate has lead 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.
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.[4] P. exclamans have also been observed occupying artificial nests put out by researchers and consisting of bundles of straws.[2]
Morphology
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. [5] . They have smoky black 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.[4] 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.[5] The extent of ferrunginous markings is variable.[5]
Development and Reproduction
Sex Determination System
P. exclamans are haplodiploid insects, as are all Hymenoptera. This means they have haploid males that produce identical haploid sperm, and diploid females that produce haploid eggs through meiosis. This has consequences for genetic relatedness within colonies, since sisters receive identical sperm if they share a father, and the normal half identical contribution from the mother. This results in sex-biased conflicts between the queen and the workers with respect to the sex ratio, with workers preferring a more female biased sex ratio, and queens preferring equal investment in queens and males.[6]
Queen Characteristics
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.[7][8] Since the queen has the same morphology as the rest of the workers in the colony [9], 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.[10] 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.[9] The queens seem to be the only ones capable of diapause.[11]
Queen Development and Determination
While there aren’t many external morphological differences between queens and workers there are some internal traits that can be signals of a wasp’s social status.[11] It was also found that caste determination is irreversibly determined by temperature during the immature stages of development. In one experiment, some wasps emerging in June were kept in long day chambers, and these had larger and therefore more active ovaries as compared to those who were incubated in short day chambers. Long day chambers are chambers set at 26°C with 16 hours of light and 8 hours of darkness. Short day chambers are chambers set at 22°C with 14 hours of light and 10 hours of darkness.[11] It is thought that this phenomenon may occur because of a juvenile hormone secretion that determines the castes and a suppression of the workers’ ovaries by environmental or hormonal factors.[11]
Queen death is not a rare phenomenon due to predation and parasitism.[12] As a result, P. exclamans has determined a way of deciding upon the next queen. In most situations the new queen is the oldest female in the nest. This was shown to be true for 9 out of 13 nests observed in one study.[13] In the remaining 4 nests where the eldest female did not become queen, 75% of the new queens were subsequently superseded by the eldest in the nest.[13] This system is similar to that used by temperate wasps. Although these observations were taken from experimental conditions where the queen was removed, this can be applied to situations that occur in nature because of the high rate of queen death.
Sexual Attraction
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.[14] 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.[14] The range of the scent was found to be around 2 metres.[14]
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.[14] Interestingly, it was also found that on some occasions, males were attracted to other male scents.[14]
Behavior and Ecology
Worker Mortality
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.[15] 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.[15] Variation inside a single colony may also occur because of the presence of different castes.[16] 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.[15] 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.[15]
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.[15]
The Queen's Role
Unlike other wasps, P. exclamans tend to have smaller nests; there are typically fewer than one hundred individuals in a given nest. Because of the size of the nest, the queen tends to be the most active individual in the nest.[17] This is because the queen has to monitor and directly control the activities of the nest. In addition to her reproductive role, the queen must also act as the pacemaker of the nest and synchronize the worker activity.[17] These last two points have recently been disputed; it has been found that the workers are self organized.[18] It has also been observed that the queen will act aggressively towards individuals that are the least active.
Satellite Nests
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.[7] 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 (5.7%).[7] 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.[7]
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.[7] If not enough workers follow the initial worker to the new nest, then it will most likely fail as a satellite.[7]
Parasitoids
Polistes exclamans live in social nests that are open combed.[19] This leaves nests very susceptible to attacks by predators and by parasitoids. Attack by parasitoids will occur in the nest brood, as the invader will attempt to insert its own offspring into the host’s nest. The two most common parasitoids are Chalcoela iphitalis and Elasmus polistis.
C. iphitalis and E. polistis
P. exclamans take several countermeasures against invasions. If the wasps detect an intruder they will violently bite and sting the location where the C. iphitalis moth has passed by.[19] This will cause vibrations inside of the nest and the wasps inside will become alarmed and will move around jerkily; this is known as the parasite dance. This will continue for up to 10 hours after the moth has been detected. If the moth is found it will be eaten immediately; however, this is not likely to happen. The moth lays its eggs in the nest, and when they hatch, they will take over the nest. As a result, many wasp pupae are aborted. This is commonly seen in the late summer when the moth is most abundant.
The second common parasitoid, Elasmus polistis, also has disastrous effects on the P. exclamans nest. Up to 80 E. polistis will hatch out of a single cell. The males emerge first, and then will exit the nest and wait until the females emerge. Once the female moths emerge, the males will mate and reproduce, quickly destroying the P. exclamans population.[20] In some cases the invading E. polistis will hide larvae in the nest so that the P. exclamans cannot find them. This is important to the survival of P. exclamans. The hosts will attempt to remove as many parasitoids as possible to prevent them from spreading to nearby nests. This defense mechanism has not been proven to be effective, as more often than not the E. polistis larvae go undetected by the hosts. In one experiment conducted, it was found that over 60% of all nests lost brood to the parasitoids E. polistis or C. iphitalis in 1981.[20] It was also observed that larger satellites have a greater risk of being parasitized. This is due to the fact that the large nests are typically older.[21] This relationship between age and parasitism can be seen with the fact that older queens’ nests tend to be parasitized more than younger queens’ nests.[15]
Alarm Response
When a predator is located the wasps will attack and attempt to prevent invasion. As mentioned above, this tends to elicit responses from others in the nest and neighboring nests. It was proposed that this might have something to do with pheromones and signaling.[22] In one experiment, pheromones were extracted from female glands and sacs and were spread onto venom paper. It was then found that females were attracted upwind of the venom paper and some even attempted to sting it. This also had a heterospecific response where others also reacted to it. While it was found that one wasp couldn’t release enough pheromones to elicit a response, if many individuals were alarmed they would elicit a response from the rest of the nest. However, this scent is not strong enough to reach other nests, and so neighboring nests must be alarmed by physical movements and wing flapping. [22]
Queen Response
After being invaded a queen may be forced to leave her nest. If a satellite has not been established, the queen may usurp another queen in a different nest. This gives them protection and a nest without having to invest any valuable resources. The queen can then use these resources on reproducing a new brood.[23]
Predation
P. exclamans has several different predators. The most dangerous predator is the bird, which will fly by and knock the nest to the ground. This was noted by the disappearance of nests, and wasp nests being found on the ground near the bird’s nest. It was also found that the bird ate the larvae from the P. exclamans nest. This attack kills the whole nest but it isn’t very effective against the adults from the colony. When attacked, the adults fly away either to another colony or a satellite colony.
Attack by the ant Crematogaster laeviuscula is different from attacks by birds. Rather than knocking down the nest, the ants swarm all over the nest and remove the brood from it. The ants destroy the entire brood but they are unable to kill the adults.[19]
Other predators attack the adults while they are foraging or traveling to satellite nests. It is difficult to determine the number of adults that are killed away from the nest because they are difficult to track. However, it has been observed that the queen's flight to the satellite nest isn't dangerous and does not reduce its survivability.[1]
The idea of group living has been discussed by many evolutionists for its costs and benefits. Alexander predicted that the cost to large groups is that they are more likely to suffer from parasitism, but at the same time, they benefit by defense against predation. This theory is not supported in the case of P. exclamans because the parasitism does not always increase with nest size and the predation rate was independent of size.[24]
References
- ^ a b Seppa, Queller and Strassmann (1892). "Reproduction in foundress associations of the social wasp, Polistes carolina: conventions, competition, and skew". Behavioral Ecology. 13 (1): 531–542. doi:10.1093/beheco/13.4.531.
- ^ a b West (1968). "Range extension and solitary nest founding in Polistes exclamans". Psyche. 75 (2): 118–123. doi:10.1155/1968/49846.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Strassmann, J. E. (1985). "Worker mortality and the evolution of castes in the social wasp, Polistes exclamans". Insectes Sociaux. 32: 275–285.
- ^ a b McIlveen & Hamman. "Paper Wasp". Texas A&M Agrilife. Retrieved 6 December 2012.
- ^ a b c Buck, Matthias. "Identification Atlas of Vespidae". University of Alberta. Retrieved 9 January 2013.
- ^ Lester and Selander (1979). "Population Genetics of Haplodiploid Insects". Genetics. 92 (4): 1329–1345.
{{cite journal}}: Text "doi" ignored (help) - ^ a b c d e f Strassman (1981). "Evolutionary Implications of Early Male and Satellite Nest Production in Polistes exclamans Colony Cycles". Behavioral Ecology and Sociobiology. 8 (1): 55–64. doi:10.1007/BF00302844.
- ^ Eickwort (1969). "Differential Variation of Males and Females in Polistes exclamans". Evolution. 23 (3): 391–405. doi:10.2307/2406695.
- ^ a b Strassmann, Lee Jr, Rojas and Baust (1984). "Caste and sex differences in cold-hardiness in the social wasps, Polistes annularis and P. exclamans". Insectes Sociaux. 31 (3): 291–301. doi:10.1007/BF02223613.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ http://en.wikipedia.org/wiki/Dimethyl_sulfoxide
- ^ a b c d Bohm (1972). "Effects of environment and juvenile hormone on ovaries of the wasp, Polistes metricus". Insect Physiology. 18 (1): 1875–1883. doi:10.1016/0022-1910(72)90158-8.
- ^ Solis & Strassmann (1990). "Presence of Brood Affects Caste Differentiation in the Social Wasp, Polistes exclamans Viereck (Hymenoptera: Vespidae)". Functional Ecology. 4 (4): 531–541. doi:10.2307/2389321.
- ^ a b Strassmann & Meyer (1983). "Gerontocracy in the social wasp, Polistes exclamans". Animal Behavior. 31 (1): 431–438. doi:10.1016/S0003-3472(83)80063-3.
- ^ a b c d e Reed and Landolt (1990). "Sex attraction in paper wasps, Polistes exclamans viereck, in a wind tunnel". Journal of Chemical Ecology. 16 (4): 1277–1287. doi:10.1007/BF01021026.
- ^ a b c d e f Strassmann (1985). "Worker mortality and the evolution of castes in the social wasp Polistes exclamans". Insectes Sociaux. 32 (3): 275–285. doi:10.1007/BF02224916.
- ^ Judd (2000). "Division of labour in colony defence against vertebrate predators by the social wasp Polistes fuscatus". Animal Behaviour. 60 (1): 55–61. doi:10.1006/anbe.2000.1449,.
{{cite journal}}: Check|doi=value (help)CS1 maint: extra punctuation (link) - ^ a b Herman, Queller & Strassmann (2000). "The role of queens in colonies of the swarm-founding wasp Parachartergus colobopterus". Animal Behavior. 59 (1): 841–848. doi:10.1006/anbe.1999.1385.
- ^ Strassmann, Joan. "What we have figured out about social insects?".
- ^ a b c Strassmann (1981). "Parasitoids, Predators, and Group Size in the Paper Wasp, Polistes Exclamans". Ecology Society of America. 62 (5): 1225–1233. doi:10.2307/1937287.
- ^ a b Lutz, Strassmann & Hughes (1984). "Nest Defense by the social wasps Polistes exclamans and P instabilis". Entomological News. 95 (2): 47–50. doi:10.1007/BF00302844.
- ^ Strassmann and Thomas (1980). "An Analysis of the interrelationships among nest varible in Polistes exclamans". Journal of the Kansas Entomological Society. 53 (4): 770–780.
{{cite journal}}: Text "doi" ignored (help) - ^ a b Post, Downing and Jeanne (1984). "Alarm response to venom by social wasps Polistes exclamans and P. fuscatus". Journal of Chemical Ecology. 10 (10): 1425–1433. doi:10.1007/BF00990313.
- ^ Cervo (2006). "Polistes wasps and their social parasites; an overview". Finish Zoological and Botanical Publishing Board. 43 (1): 531–549.
{{cite journal}}: Text "doi" ignored (help) - ^ Alexander & Borgia (1978). "Group Selection, Altruism, and the Levels of Organization of Life". Annual Review of Ecology and Systematics. 9 (1): 449–474. doi:10.1146/annurev.es.09.110178.002313.