Asian Hornet – Vespa velutina
As many of you will know the Asian hornet has now been found in the UK.
Your committee have taken the view that our area will be invaded sooner rather than later. We must therefore take steps to inform ALL of our members of the potential dangers as well as the way forward with ways to combat the threat.
Asian Hornet Poster issued by the GB non-native species secretariat (NNSS)
Asian Hornet Alert also issued by NNSS
A Simple Monitoring Trap for the Asian Hornet issued by The National Bee Unit, Crown Copyright
As with our native hornet, Vespa crabro, only the fertilised queen will overwinter. From February onwards the queens will emerge on warm days to feed on sweet foods to raise their energy levels. This means that sweet baits are highly attractive at this time of year to lure queens into traps.
Every queen hornet trapped in the spring will reduce the number of hornet nests in the area and reports from France suggest reductions of up to 90% may be achieved.
You can find a PDF “A Simple Monitoring Trap” above courtesy of the National Bee Unit.
6000 hornets in an average nest!
Asian hornet nests are very large and usually found in tall trees but man-made structures may also be used. An average nest may have 6000 hornets and in July the workers will start raiding honey bee colonies to obtain protein food for feeding to larvae. At this time of year traps should use a protein lure. This situation may continue into November.
Around September the colony will start to produce queens and drones. 350 queens will be produced on average and these mated queens will hibernate over winter while the rest of the colony dies out. Thus traps deployed in the autumn will help reduce the hornet population the following year.
- Slightly smaller than our native hornet. Workers up to 25mm long (1”).
- Dark abdomen, 4th segment yellow.
- Yellow ends to all legs.
- Thorax entirely black/brown.
We strongly recommend that beekeepers sign up to BeeBase. In the event that the Asian hornet arrives in our area, efforts to contain it will be seriously hampered if the NBU don’t know where vulnerable apiaries are located. Affected beekeepers will also receive notification by email.
More information on the Hornet Meetings page
Professor Stephen Martin at University of Salford has recently published a book called The Asian Hornet – Threats, Biology & Expansion. Here are some of the observations of an expert who has been studying hornets since 1987.
The life cycle is similar to wasps and bumble bees. Queen hornets mate in the autumn and hibernate in a safe niche protected from rain, snow and wind. During hibernation queens fold their wings under their abdomen, pressed against their body, giving them a distinctive appearance. The queens will come out of hibernation as the weather warms.
The queen’s fat reserves will be low so she seek nectar and tree resin to activate her ovaries and sustain nest building activities. During the next few weeks she hunts for a suitable nest site, usually enclosed and protected, then begins the building process using wood fibres. The nest hangs down and is attached to the substrate at the top by a stalk or petiole. The lower end of the stalk forms the hexagonal cells for brood rearing. They hang down with the open end at the bottom. The entire structure is surrounded by a thin wood fibre (paper) envelope and at this stage may be 4 -5cm across.
When this proto-nest is finished the queen lays an egg at the base of each cell attached to the cell wall by an adhesive. Hatching in 3 to 4 days the larva initially remains attached to the old egg case to prevent falling out of the cell. Eventually the larva grows big enough to fill the whole cell, spins a silken cocoon and pupates. It takes about 50 days for the lone queen to build the proto-nest and at this stage the time from egg to adult worker may take 50 days as the nest is too small to thermoregulate.
When the first workers appear there is a short ‘co-operative’ period around June when both workers and queen are active outside the nest. As the colony numbers increase the queen stays in the nest and becomes the egg layer.
June to August sees rapid expansion in nest size and colony numbers and if the original location is too small the whole colony may re-locate to a more suitable site, in a tree or under the eaves of a tall building. This process may only take a few days.
During the ‘reproductive phase’ (September to October) the nest is large enough to thermoregulate at around 30°C and the time from egg to adult reduces to 29 days. Some larger cells will be created for the queen to lay unfertilised eggs that will become drones and fertilised eggs that will be queens. Numbers of queen and drone hornet produced vary considerably, largely dependent on climatic conditions. 300 queens and 600 drones are possible but with favourable conditions these numbers could treble!
These ‘sexuals’ stay in the nest for a week or so building up their fat reserves then leave the nest without an orienting flight as they will not return. After mating, the fertilised queen seeks a safe place to hibernate, the drones die and the nest goes into decline. The whole Asian hornet cycle takes 8 – 10 months compared to 5 -6 months for the European hornet.
How to protect your bees
Professor Martin argues that the only proven method of hornet control is colony discovery and destruction. Neither task is easy. The advice given in the book is to call in the professionals! Never attempt to remove or kill an Asian hornet nest yourself. If things go wrong you put yourself and others in grave danger, even of being killed as has happened in France. We have a long way to go before an effective strategy emerges to protect our bees and the public from this very successful alien species.
See the Library Page for details of The Asian Hornet – Threats, Biology & Expansion