This year, extreme heat came early. Since insects depend on the temperature to become active, they’re already very busy around us. That’s especially the case with social wasp queens. Those insects, larger than the workers we see in the fall, have woken up from their winter state of torpor looking for nectar and a place to build their nests. Recent sightings of the Asian Giant Hornet (Vespa mandarinia) in Canada have also surprised a number of you, who are concerned about that insect take up residence in Québec. How can we distinguish hornets from other social wasps, and above all, what’s the situation involving the presence of hornets in our province?
A question of color…and dimension!
Hornets and social wasps are Hymenoptera belonging to the subfamily Vespinae. In Québec there are 14 native Vespinae species (nine species in the Vespula genus and five in the Dolichovespula genus), and one introduced species in the Outaouais region: Vespa crabro, commonly called the European Hornet. With the exception of a few Dolichovespula species, which are black and white, the great majority of our social wasp species are black and yellow in color. Also, although the European hornet resembles our social wasps, its head and thorax, generally, are more brownish. Also, the hornets have a particular feature on the head, which when seen from above reveals an area located behind the compound eyes that’s much broader than in other Vespinae.
When we compare our native species with the introduced Vespa crabro species, the difference is also…about size! Specifically, most of our native species measure between 7 and 18 millimeters (including the queens). A Vespa crabro worker has a size that varies from 18 to 25 millimeters ‒ and the queen can reach as much as 40!
All these species of social wasp make a globular nest of grey paper to house their colony. But here again there are differences to be noted: wasps in the Vespula genus generally build their nests in the ground, while the Dolichovespula construct above-ground nests exposed to the elements (in tree branches, under eaves, and so on). The introduced Vespa crabro species, meanwhile, chooses a preexisting cavity in a tree, a wall, or else in old abandoned barns. This species very rarely settles in the ground.
European and Asian hornets: keep an eye out!
In the fall of 2019, members of the Vespa mandarinia or Asian Giant Hornet species were observed in Nanaimo, British Columbia. A native of the Far East, this species is a new arrival on the American continent. It’s the biggest of all hornet species: the workers measure from 25 to 40 and the queens from 45 to 55 millimeters! The species feeds exclusively on insects, in particular on honey bees. We think that Vespa mandarinia may be able to survive our winters, but for the time being the species hasn’t definitively settled in. In any case, specialists are keeping close watch on its presence on the continent to prevent its establishment.
It’s quite a different story for the European Hornet, because this species was found for the first time in Québec ‒ in Aylmer ‒ in 2004. It has since been sighted in the province every year and seems to have settled in for good. The European Hornet is encountered primarily in wooded areas, where it feeds on insects and spiders. It’s rarely a nuisance and is not particularly aggressive. As with all Vespinae species, you nevertheless have to avoid getting close to its nest, because its bite is painful (notably owing to the diameter of its stinger). It’s not fatal, however, even when a person is attacked by several dozen hornets, unless he or she is allergic to the venom.
Useful despite everything!
Our native species of social wasps feed their larvae on various insects and other sources of animal protein. They themselves feed on sweet substances like plant nectar. Although insects can seem threatening to us, we mustn’t forget that these are efficient pollinators as well as voracious predators that control other insect populations. Their ecological roles are therefore essential ‒ which is why it’s important to protect them well.