Asian giant hornets in Nanaimo

Staffan Lindgren

Three specimens of the Asian Giant Hornet, Vespa mandarinia, have been found in Nanaimo this year. The first two specimens were found by a bee keeper, whereas the third was reported to Nature Nanaimo. I collected the specimen and pinned it so that it could be properly identified. There are a number of Asian hornet species, some of which are fairly similar. For example, the specimen found in Vancouver some time ago was Vespa soror rather than V. mandarinia. These differ very slightly in colouration, but that varies with region making identification less than trivial. 

Figure 1. Asian giant hornet (photo by KENPEI).

The Asian Giant Hornet (aka Japanese Giant Hornet) is a eusocial wasp with a life cycle similar to other Vespinae. Queens, which can exceed 5 cm in length with up to 7.6 cm wingspan, overwinter and establish a nest in the spring. Once there are enough worker hornets, which are smaller than the queen but otherwise identical, Vespa mandarinia in particular, carry out raids on honey bees. European honey bees (Apis mellifera) lack defense against the hornets, and in Japan, giant hornets are major pests of apiaries. The Asiatic honey bee, Apis cerana, is able to prevent attack by killing the scout hornet. They do this by surrounding the hornet in a ball and buzzing, which increases the temperature to the point that the scout hornet dies. If they fail, the scout will recruit other hornets, and the hive will be attacked.

Asian giant hornets have stingers (modified ovipositors) connected to a venom gland, just like other Vespids. The venom is not necessarily more potent than that of other wasps, but the dose is higher. Asian giant hornets kill dozens of people each year in Japan, which is another reason to make sure that we keep these insects out. It should be noted, however, that stings by yellowjackets also kill people, mainly through anaphylactic shock. For example, between 2000 and 2017, an average of 62 people died per year in the United States due to yellowjacket, hornet and bee stings.

If you see a large wasp with a yellow or light orange head, please report immediately to the Canadian Food Inspection Agency. If you are able to capture, or at least photograph the insect, identification can be confirmed, which is important.