Polistes

From Wikipedia, the free encyclopedia

Polistes
Polistes dominulus
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Hymenoptera Family: Vespidae Subfamily: Polistinae Genus: Polistes Latreille, 1802

Wasps of the cosmopolitan genus Polistes are the most familiar of the polistine wasps, and are the most common type of paper wasp. It is also the single largest genus within the family Vespidae, with over 300 recognized species and subspecies. Their innate preferences for nest-building sites leads them to commonly build nests on human habitation, where they can be very unwelcome; although generally non-aggressive, they can be provoked into defending their nests. All species are predatory, and they may consume large numbers of caterpillars, in which respect they are generally considered quite beneficial. The European paper wasp, Polistes dominulus, was introduced into the US about 1981 and has quickly spread throughout most of the country, in most cases replacing native species within a couple of years. This species is very commonly mistaken for a yellowjacket, as it is black strongly marked with yellow, and quite different from the native North American species of Polistes. Polistes can be identified by their characteristic flight; their long legs dangle below their body, which is also more slender than a yellowjacket.^[1]

Contents 1 Life-cycle 2 Behavior 2.1 Dominance hierarchy system 2.2 Nestmate recognition 3 Pest status 4 External links 5 References 5.1 Notes

[edit] Life-cycle

The general life cycle of Polistes follows a cycle that can be divided into four phases^[2]:

1. Founding (or pre-emergence) phase
2. Worker phase
3. Reproductive phase
4. Intermediate phase

The founding stage involves a solitary female (foundress) initiating a nest, building 20-30 cells before initially egg-laying. This phase begins in spring, depending on climatic conditions. The foundress (or foundresses) begins by fashioning a petiole and produce a single cell at the end of it. Further cells are then added around this, 6 cells surrounding it to produce the characteristic hexagonal shape of the cells.

After the hatching of the first larvae, the foundress progressively provisions (brings food multiple times throughout development) the larvae with softened caterpillar flesh, halting further egg-laying until some of the larvae have pupated. These larvae will eventually hatch to become first generation workers.

Rather than founding her own nest, a foundress can also choose to attempt to usurp a nest of a similar species, or join similar species upon another nest. In the case of the latter, evidence shows that such co-founding females are generally, but not exclusively, closely-related.^[2]

The worker phase usually begins in early summer, roughly 2 months after colony initiation, with the emergence of the first workers. On emergence, the workers take up most of the colony's foraging, brood care and nest maintenance. Typically at this stage, the auxiliary (subordinate) females are driven from the nest, leaving the alpha female and newly emerged workers.

Emergence of the first female reproductives (gynes) is taken to signal the start of the reproductive phase of the colony. The reproductives differ from workers produced at this latter phase of the colony by having increased levels of fats stores to allow them to survive the over-wintering period, as well as having increased levels of cryoprotectant carbohydrate compounds for the same purpose. In some species, a very small number of these future nest-founding females may be produced among the worker brood, rather than having a truly distinct reproductive phase.

Finally, the "intermediate" phase is just the period in which the gynes and males mate and then disperse from the birth colony, before over wintering (hibernating) until the start of the next colony cycle. Typically this period is characterized by a decline in brood care and foraging, as well as fewer workers (due to mortality, without workers being replaced by newly-hatched brood). In temperate species such as P. dominulus the colony disperses in the late summer and individuals frequently cluster in groups of up to 50 (called a hibernaculum) over winter. Hibernation does not usually take place on former nest sites.

[edit] Behavior

[edit] Dominance hierarchy system

Main article: Polistes dominulus

Morphologically, there is little difference between the foundress and subordinate reproductive members of the colony. However, several studies have shown that behavioral differentiation occurs among females both between and within generations. This has been best-studied in P. dominulus.

[edit] Nestmate recognition

Polistes discriminate colony mates using an acquired (i.e. learned) cue, absorbing hydrocarbons from the natal nest at eclosion.^[3] 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 looked into the molecular basis of the recognition "pheromone" used by the wasps, and indicate that at least some of the recognizable labels have the same chemical constituents as the adult cuticular hydrocarbons.

Dominant individuals of P. dominulus have differing cuticular profile to workers,^[4] and the frequent observations of the dominant female stroking its gasters across the nest surface, combined with its staying on the nest for longer times than subordinates, suggests that the dominant individual may contribute more to the nest odor.

A study of P. carolina showed that females do not preferentially feed their own progeny (as larvae),^[5] so it may be the case that nest odour only serves as a likely indicator of relatedness, rather than a specific label of kinship.

Further to this recognition of nest-mates, a study on Polistes biglumis illustrated how foundresses discriminate between 'alien' eggs and their own, via differential oophagy.^[6] Interestingly, the discrimination focused upon eggs destined to be reproductives, with 'alien' worker destined eggs allowed to remain on the nest. The authors speculated that the benefits of allowing worker destined eggs to remain (and so hatch to become workers which will then aid the colony) outweigh the costs of initially provisioning the resultant larvae.

The mechanism of differentiation was not elucidated, but was thought to be based upon differences in cuticular hydrocarbon odor. Whether the discriminatory oophagy was a result of decreased tolerance of alien odors during the later, reproductive phase of the colony cycle, or an actual discrimination between worker and reproductive destined eggs, remains to be supported with good evidence.

[edit] Pest status

Along with the German and common wasps, the Asian and Australian paper wasps (Polistes chinensis and P. humilis) are considered pests in New Zealand. Arriving in 1979^[7], the Asian paper wasp has established itself on both the North and northern South Island. Because it competes with native species (such as the Kākā) for insects, nectar and honeydew (Clapperton, 1999; Kleinpaste, 2000)^[8], it is a hindrance to conservation efforts.

[edit] External links

• Paper wasp Polistes dominulus reference photographs, descriptions, taxonomy
• Paper wasp Polistes fuscatus diagnostic photographs, natural history
• Polistes dominulus facial markings indicating dominance

[edit] References

• S. Turillazzi and M. J. West-Eberhard (1992). "The Natural History and Evolution of Paper-Wasps". 
• Karsai I. & Theraulaz G. (1995). Nest building in a Social Wasp: Postures and Constraints (Hymenoptera: Vespidae). Sociology 26 (1): 83-114. 
• Karsai I. & Penzes Z. (1996). Intra-specific variation in the comb structure of Polistes dominulus: parameters, maturation, nest size and cell arrangement. Insectes Sociaux 43: 277-296. 

[edit] Notes