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|male D. media|
The median wasp, Dolichovespula media, is a wasp of the genus Dolichovespula native to Europe. Aside from its black-and-yellow coloration, it is very similar to the North American species Dolichovespula maculata, the bald-faced hornet.
The median wasp is a large, social wasp, it is the second largest British wasp with only the European hornet Vespa crabro being larger. Queen median wasps resemble V. crabro too having a mainly yellowish-orange colouration. The workers are coloured like other related social wasps but some have very dark gasters with narrow yellow bands. A useful feature, in all castes, for identifying median wasps from other social wasps are the yellow markings on the anterior part of the thorax which are said to resemble the NIKE logo, or when viewed from above look like two mirrored numeral 7s.
The median wasp is very catholic in its choice of habitat but it prefers lowland areas and in the recently colonized Great Britain the majority nests are from private gardens, often from major conurbations.
Median wasps build nests in aerial sites, almost always suspended from the branches of trees and shrubs, from ground level to a height of several metres. The leaves of the host tree or bush camouflage the nest and protect it from rain and direct sunlight. Occasionally nests are built attached to the walls of houses or other man made structures. The nests are created using wood fibres collected from both sound and apparently rotten timber (workers have been observed visiting weathered fence posts for the purpose). In the spring and early summer, embryo (or queen) nests have a long, spout-like vestibule to the entrance at the bottom of the nest; this feature is lost later in the season as the nest expands. Queens hibernate in and under logs, perhaps indicating that the queen prefers a humid site in which to overwinter.
In the spring, queens visit wall cotoneaster, blackcurrant and rhododendron flowers. As the season progresses, males and workers visit many other flowers. Workers also feed on honeydew on leaves, 'oak flux', and exudations from trees containing goat moth Cossus cossus caterpillars. For the queen and to feed their young larvae, they hunt many kind of insects — such as flies and other wasps.
Although their nest's life cycle is short, future queens (gynes) can survive through the winter, and the result is multiple egg-laying queens that abandon the mother nest in search of a new nest.
The median wasp is found throughout the Palearctic from Great Britain to Japan in temperate regions. The colonisation of Great Britain is a recent phenomenon and the species was not recorded there until they were seen in Sussex in 1980. They have since spread and have spread as far north as Cumbria and Durham by 1995 and with recent isolated records in Scotland. A single male median wasp was found in Raglan, Waikato, New Zealand but no other specimens have been found in New Zealand.
- Edwards, R., ed. 1997. Provisional atlas of the aculeate Hymenoptera of Britain and Ireland. Part 1. Bees, Wasps and Ants Recording Society. Huntingdon: Biological Records Centre.