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Asian Hornet

Vespa Velutina also known as the Asian Hornet

Confirmation of an Asian Hornet find in Scotland strongly suggests a need to look out for its arrival in Ireland. We heartily encourage all beekeepers to watch out for this invader. This follows the confirmed finding of an Asian Hornet nest in Gloucestershire towards the end of last year. That nest was destroyed and there have been no further confirmed sightings until now. But, it looks like they are on their way.

Some helpful tips and advice on how to make your own trap can be found in the BeeBase fact sheet. Clicking here will give an automated download:

http://www.nationalbeeunit.com/downloadDocument.cfm?id=869

BeeBase has also given Information from beekeepers in France that shows that nest numbers are reduced by more than 90% in areas where traps are set in springtime. Should the Asian Hornets become established anywhere in Ireland or the UK, springtime trapping will become a very useful management tool. When hanging out traps, please remember that it is important that damage to native Irish wasps, hornets and any other insects is kept to an absolute minimum.

What is the Asian Hornet?

Vespa Velutina has become an invasive species in France where it is believed to have arrived in boxes of pottery from China in 2004. Humans have been attacked after disturbing hornets; although the species is not aggressive it “charges in a group as soon as it feels its nest is threatened”. People have been hospitalised in France after suffering anaphylactic shock as a result of multiple stings. Because of hornets’ larger size, their sting is more serious than that of a bee.

Like other hornets, Vespa velutina builds nests that may house colonies of several thousand individuals. Females in the colony are armed with formidable stingers with which they defend their nests and kill their prey. The nest is of paper, roughly in the shape of a huge egg, usually at least half a metre in length. Unlike the nest of the European hornet, Vespa crabro, its exit is usually lateral rather than at the bottom. The nesting season is long, and a colony commonly begins by building a nest in a low shrub, then abandoning it after some months and rapidly building a new one high in a tree, possibly as an anti-parasitic measure. The next generation of young queens disperses in the late autumn to hibernate over winter.

Vespa velutina opportunistically hunts a very wide range of insects, including flies, dragonflies and Orthoptera, typically capturing them by pursuit. The major concern about their invasiveness however, is that when they find a bee colony or an apiary, they tend to settle down and specialise in honeybees as their prey. A hornet occupies a position above a beehive as its hunting territory. It flies about within an area of about half a square metre, scanning the direction from which foraging bees return to the hive. Each hornet vigorously defends its hunting territory, chasing off any rivals. However, as soon as it catches a bee it flies off and another hornet replaces it, usually within a few seconds. The circadian activities of the two species of honeybees are similar, and the hunting hornets match them; their most intense activity is in the morning and afternoon, not near dusk or noon.

In their native range Vespa velutina mainly hunt Apis cerana, the Eastern honey bee, which has evolved a strategy of avoiding hovering hornets by rapid entry and exit from the hive when hornets are about. The guard bees also ball hornets to death. However, where the European honey bee has been imported, Vespa velutina finds them easier prey than Apis cerana because Apis mellifera have not been subjected to selection for countering concentrated hawking by hornets. For example, Apis mellifera approach their hives more indirectly and slowly when they detect hawking hornets, instead of darting in as fast as possible in the way that Apis cerana does. They also ball hornets to death in the way that Apis cerana do, but less effectively, and they do not achieve as high a temperature in the ball. Furthermore, when they detect that hornets are hawking, Apis cerana tend to withdraw into the nest and Apis mellifera do not.

Apis cerana guard bees also use wing shimmering in response to the presence of Vespa velutina. This is a very generalised response to disturbance and has variously been suggested to be an aposematic signal or a strategy for disruption of visual patterns, similar to the behaviour of Apis nuluensis and Apis dorsata. Apis mellifera exhibits no such behaviour.

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