The Asian hornet (Vespa velutina nigrithorax) is an exotic invasive species which mainly poses a threat to other insects in our ecosystem, particularly honeybees, which it feeds on.

Apart from the effect on the insect population and beekeeping, another significant effect is on agricultural activity. The species is most active in September, when worker hornets not only feed on other insects but also take to fields with fruit trees. The Collserola Natural Park saw the effects of the species in different vineyards and fruit plantations in 2018.

Risk for the population

Asian hornets make two types of nests: primary nests (smaller and sheltered from the rain) and secondary nests (much larger and generally in high places, although they can be found at ground level).

Queen hornets which have hidden in the winter start new colonies in the spring, with small nests to breed the first worker hornets in. After the summer, these will build the secondary or definitive nest. These nests can be found in the cornices of rooftops, garages, porches and abandoned hives, in other words, inhabited places.

Secondary nests are like a huge ball of paper and can measure more than 60 cm in diameter. They are normally built on the highest branches of trees but can also be found in abandoned buildings or even on the ground.

Groups of the population at risk are:

• People with allergies
• Beekeepers
• Gardeners, forestry and agricultural workers. People should also be cautious when gardening at home or carrying out tasks at municipal allotments.

What do I do if an Asian hornet stings me?

You need to treat stings in the same way as any other insect bite or sting. Check the recommendations from the Catalan government’s Ministry of Health.

In the case of stings from Asian hornets (must be previously identified), call 061 in the following scenarios:

• You have more than one sting or the sting is inside your mouth.
• You are allergic to this hornet or you do not know if you are.

What should I do if I find an Asian hornet’s nest?

In the presence of individual hornets or nests, act the same way as with autochthonous wasps, hornets and bees. If you detect isolated individuals, you should check if there is a nest nearby. If you find a nest in public space, call the civic behaviour number (900 226 226) to activate the service to remove and eliminate the nest. This service is offered in line with the directives from the Government of Catalonia and conducted by specialist beekeepers, who will try to eliminate as much as possible, although the invasive species cannot be completely eradicated.

For nests found on private property, the owner is responsible for getting them removed and should contact a company specialising in beekeeping.

Nests are not dangerous if left alone. Isolated hornets which are far from the nest will not attack people either, unless they are disturbed. It is therefore important not to do anything to the nest under any circumstances, and to keep a safe distance of a few metres. For stings, act the same was as you would with a bite or sting from any other insect. Call 061 if you have multiple stings, if the sting is inside your mouth or if you are allergic to this hornet (or you do not know if you are).

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