Vespula germanica

Vespula germanica (European wasp, German wasp, or German yellowjacket) is a species of wasp found in much of the Northern Hemisphere, native to Europe, Northern Africa, and temperate Asia. It has been introduced and is well-established in many other places, including North America, South America (Argentina and Chile), Australia, and New Zealand. German wasps are part of the family Vespidae and are sometimes mistakenly referred to as paper wasps because they build grey paper nests, although strictly speaking, paper wasps are part of the subfamily Polistinae. In North America, they are also known as yellowjackets. Vespula germanica belongs to the genus Vespula, which includes various species of social wasps that are found throughout the Northern Hemisphere. In North America, these wasps are most commonly known as yellowjackets, but this name also applies to species within the sister genus Dolichovespula. Members of Vespula are often confused with other genera, especially the paper wasp Polistes dominula. Colonies of V. germanica share many characteristics with those of V. vulgaris (common wasp) and V. pensylvanica (western yellowjacket), so they are very often studied together. The German wasp is about 13 mm (0.5 in) long, has a mass of 74.1 ± 9.6 mg, and has typical wasp colours of black and yellow. It is very similar to the common wasp (V. vulgaris), but unlike the common wasp, has three tiny black dots on the clypeus. German wasps also have black dots on their abdomens, while the common wasp's analogous markings are fused with the black rings above them, forming a different pattern. However, the identification of a wasp as V. vulgaris may be difficult because the normally unbroken black mark on its clypeus can sometimes appear broken, making it look extremely similar to V. germanica. V. germanica originated in Europe, Asia, and North Africa and can now be found in sections of almost every continent. It has established populations in North America, South America, South Africa, New Zealand, and Australia. German yellowjackets are known to be especially successful and destructive invaders of new territories. These wasps are polyphagous predators which feed on native arthropods, and because they are able to outdo many other animals for food, they have caused considerable harm to the indigenous wildlife of areas which they have invaded. For a given year, V. germanica disperses at distances of no more than 1000 m, so that their rapid dispersal is likely to be aided by accidental human transport of hibernating queens. This normally leads to a bottleneck effect during the establishment of new populations, which explains the significant genetic differentiation often found among geographically distant populations. The nest is made from chewed plant fibres, mixed with saliva. The majority of nests are found in the soil below ground. A significant portion of nests are found in artificial structures such as attics, and a small portion are found above ground. A single queen initiates a nest in the spring by constructing an embryonic nest, which contains a series of hexagonal cells. These cells are used to house one wasp through the immature stages of life: egg, larval instar, and pupa. The colony grows rapidly during the summer with a huge increase in worker numbers and nest size. By the end of summer, the rate of growth slows considerably and more males are produced than workers, and the focus is shifted from building small cells to building cells that are 30-40 percent larger. These new cells house the new queens and males. In the fall, the new queens begin hibernation, while the old queens die off and the colony collapses. In some cases, the nests may survive through the winter and reach the next season. If this occurs, the nest will become polygynous and reach a much larger size than in the previous year. V. germanica nests are strongly affected by climate. Average colonies in Australia contain over 9500 small workers and 3600 large queen and male cells. By the end of May, colonies in Australia have 15,000 wasps emerging from small cells and 2500 wasps emerging from the large cells. By comparison, nests in the British Isles only have 6100–6500 small cells and 1500 large cells on average, in roughly eight combs. Additionally, a significant number of nests in Australia are able to survive the winter, whereas in England none of the nests survive. This demonstrates how V. germanica nests can reach a substantial size in appropriate climate conditions. High variation in the sequence and diversity of tasks performed by V. germanica workers suggests limited temporal polyethism exists within the species. Temporal polyethism is a mechanism in which workers specialize on tasks in a sequential order throughout their lives, instead of performing numerous tasks concurrently. The typical order of tasks in V. germanica is nest work, pulp foraging, carbohydrate foraging and protein foraging. Approximately 61 percent of the wasps observed perform more than two of these tasks during their lifetimes. Additionally, about 40 percent of the wasps specialize on only one task per day, but these individuals varied with respect to age and sequence of task performance. The schedule of temporal polyethism found in V. germanica is highly accelerated when compared to other Hymenoptera, which is likely related to worker lifespan. Vespula workers may not live long enough to benefit from a strict system of worker specialization in which workers repeatedly perform one task.