Overview

Brief Summary

Vespula pensylvania, the western yellowjacket, is a social, ground-nesting wasp native to western North America. They aggressively protect their nests, and, like other vespid wasps, can sting repeatedly. Adult workers forage continually for high protein foods, mostly small insects, caterpillars, and spiders, and they sometimes scavenge on dead animals to feed their brood. Vespula pensylvania is found in all states west of the Rocky Mountains, from Mexico up through western Canada. Although it has a more limited distribution than either the closely-related and biologically similar common yellowjacket Vespula vulgaris or the German yellowjacket Vespula germanica (which have both recently become major pests in non-native habitats around the world, especially in the southern hemisphere) V. pensylvania also has a high potential for invasiveness. Since 1919 there have been sporadic reports of the western yellowjacket in Hawaii, and in 1978, populations there exploded to become a public nuisance and threat to endemic Hawaiian insect fauna. A western yellowjacket queen starts to build a nest in the spring, which matures into a large colony of up to several thousand workers by fall. At this time the colony declines and only new queens overwinter. However, in warm climates, such as California and Hawaii, colonies can survive longer than the several summer months they last in their native range, growing to enormous size with the potential to devastate surrounding insect populations and create a large, difficult to control public nuisance. If their nests can be located, physically or chemically destroying them are effective means of population control. Toxic baits, in which attractants are laced with insecticides and offered to workers to feed to larvae and the queen can also be successful in destroying a colony. Baited traps are also used to monitor and assess population numbers. Although Vespula pensylvania has similar yellow and black coloration patterns to other yellowjackets (wasps of the genera Vespula and Dolchivespula), the complete yellow ring around their eye is a reliable distinguishing characteristic. (CABI 2011; Kweskin 2009; Wikipedia 2011)

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Comprehensive Description

General Description

This species is black with yellow markings. The metasomal pattern is similar to V. germanica but Western Yellowjacket is the only species with a yellow ring around the compound ayes (Buck et al. 2008). In average the worker size is 15 mm (Gruner & Foote 2000). Head: Malar space less than half as long as the penultimate antennal segment; occipital carina complete; deeply emarginated subantennal mark on the frons. Metasoma: apex of 7th tergite depressed; tergum 7th densely pubescent apical margin; shaft of edeagus without sharp teeth at base of terminal spoon, aedeagus with slender preapical portion. Xanthic specimens are rare (Miller 1961, Buck et al. 2008).
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Distribution

Western Yellowjacket is native of western half of temperate North America in Canada, United States, Mexico and this species was introduced in Hawaii (Kweskin 2000, Carpenter & Kojima 1997). Canada: from Manitoba to British Columbia. United States: from western to Colorado, Nebraska, Texas and Wisconsin. México: Baja California Norte, Ciudad de Mexico and Michoacan (Buck et al. 2008).
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Ecology

Habitat

Open boreal forest, forest edges and prairies. Urban zones as gardens, parkland, meadows and houses.
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Trophic Strategy

They feed regularly on live prey. They are mostly predators of spiders, harvestmen, caterpillars, flies, hemipterans, soft beetles, butterflies, moths, crickets, slug and other bugs. This species avoids hard beetles. The adults carry their prey or part of them to the nest to feed their larval states. They also feed of flower nectar or sweet substances as aphid honeydew, they have been reported collecting dead honey bees and this species has affinity to scavenge in carrion (Akre et al. 1976, Kweskin 2000).
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Life History and Behavior

Cyclicity

In natural populations in cold zones the colony is annual, but in colonies inside buildings the wasp survive the winter.
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Life Cycle

The Western Yellowjacket is a social species with annual colonies. In early April or late May the queens emerge from diapauses and them looking for nesting places, generally they fly 20 cm above the ground; most queens begin the nest in deserted rodent burrows, but they are also built in other dark cavities like hollow walls and attics (Akre et al. 1976, Akre et al. 1981, Buck et al. 2008). The successful queen burrows about 10-30 cm underground, aerial nest are uncommon. The queen adds cells inside the nest, she lays eggs and takes care of the larvae, the first workers emerge in early June and the queen doesn’t leave the nest again. The workers search food and fibers, care the larvae, clean the cells, feed the queen, the larvae and the males, they exhibit trophallaxis, mauling and ovoposition behavior, and also they protect the colony (Akre et al. 1976). The average of lifespan of a worker is 34 days. The males emerge in mid August, finally the colony decline in later  September (Akre et al. 1976).
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Vespula pensylvanica

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 6
Species With Barcodes: 1
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Conservation

Conservation Status

This species is very common and this is not reported in vulnerability status.
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Wikipedia

Vespula pensylvanica

The western yellowjacket (Vespula pensylvanica) is a species of wasp in the genus Vespula.[1]

Description[edit]

V. pensylvanica is a predatory species that feeds on a wide range of invertebrate taxa (and occasionally even on slugs[2]) and this has great potential for negative impact on the native fauna in insular habitats.[1] In its genus, it is one of the few species that also has a scavenging habit as opposed to a strictly predatory habit and is thus considered a major pest to humankind. Along with two other species — the "common wasp" or "yellowjacket" (Vespula vulgaris) and the "German wasp" or "European wasp" (Vespula germanica) — V. pensylvanica is part of the "Vespula vulgaris species group" which together are the most abundant and bothersome of eusocial wasps species.[3] With a predilection for scavenging carrion that attracts it to the human food and garbage, V. pensylvanica is the most significant pest yellowjacket in western North America.[2]

Vespula pensylvanica shares its basic yellow and black pattern with other species of wasp in genus Vespula and its sister genus Dolichovespula which are collectively known in North America by the common name "yellowjacket." V. pensylvanica, however, is the only member of its species group that has a complete yellow eye ring around each compound eye.[2][4] This eye ring is also visible in queen wasps of this species.[1]

Occasionally, the eye loop is entirely absent in males; it can be broadly interrupted in both sexes but rarely so in females.[2] Males without a yellow eye loop can be distinguished from V. germanica by more subtle morphological differences, viz, "the deeply emarginate or spotted subantennal mark on the frons, the slender preapical portion of the aedeagus, and the much more densely pubescent apical margin of tergum".[2] The majority of females of Vespula squamosa also have a narrow eye loop but this species shows a radically different metasomal pattern.[2] the majority of western yellow jackets are blind, except for the queens

The length of this species's fore wing is 8.5–10.5 mm in workers, 12.5–14.5 mm in queens, and 12.5–14.0 mm in males.[2]

Range[edit]

Even though the specific name given it by Henri Louis Frederic de Saussure is "pensylvanica",[4] this species is actually native across the western half of North America, in temperate zone climates.[1][4] More precisely, individuals have been identified in Canada from Manitoba to British Columbia. The easternmost record for V. pensylvanica is a single record from Ontario but it is apparently not established in that province as a species. In the United States the eastern edge of its range is in Wisconsin, Nebraska, Colorado, and Texas. In Mexico it is known from Baja California Norte, México, and Michoacán.[2]

Invasiveness[edit]

In the Hawaiian Islands and other areas V. pensylvanica has been recorded as an introduced species. Attempts to eradicate this species from Hawaii using the toxicant bendiocarb began almost as soon as a population was discovered there in 1977. A 1988 paper revealed that V. pensylvanica was successfully attracted to canned Figaro brand tuna cat food laced with micro-encapsulated diazinon as well as, to a lesser extent, the same cat food laced with amidino-hydrazone. The color of the dispensers from which the bait was offered proved critical; translucent white dispensers were most effective.[1]

References[edit]

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