In December 2019, a Washington resident sent in a large dead hornet to the Washington State Department of Agriculture. This hornet was identified as Vespa mandarinia, the Asian giant hornet. It can be identified by its large size, yellow to orange head with black eyes and straight yellow or black lines on its abdomen.
The Asian giant hornet is the world’s largest hornet. It is native to Asia and a pest of the European honeybee. The hornet is a social insect with large colonies but only one queen. They make their nests below ground in preexisting cavities that have narrow openings. Since they are underground, they can be difficult to find. Control efforts are focused on eliminating the queen and destroying the nests where the colonies reside.
In Japan, queens that have emerged from overwintering like to visit oak trees to eat sap from any wounds present. They are aggressive protectors of their food sources and will chase off other competitors. Like other hornets, the Asian hornet is predatory and hunts primarily arthropod prey. Unlike other hornets, the Asian one will organize mass attacks against nests of other social insects in the Hymenoptera family. Hornets begin these attacks when one foraging worker secrets a hormone on the nest of the target hive. Anywhere from two to 50 nest mates will participate in the attack, and once the nest’s defense system is overwhelmed, the Vespa mandarinia will occupy it and will harvest the brood for almost two weeks. They aim these targets later in the season when nests are ramping up reproduction. Luckily, this insect has only been confirmed in Washington near the Canadian border. Vespa mandarinia is not established in North America at this time. But there are look-a-likes here that make people wonder if it made its way here. Two that stand out are cicada killers, Specius speciosus, and the European hornet – Vespa crabro. Cicada killers have their nest in the ground, but they are only aggressive if threatened. If you disturb a nest, the males put on a show, but they cannot sting you. The females do have stingers, but they use them on cicadas or other large insects. This wasp is black with a few light-yellow markings and a narrow, pointed abdomen. They are generally harmless.
European hornets have broad yellow bands on dark brown abdomens with russet hairs on the thorax. They make tan-colored paper nests inside voids in hollow trees, between walls, or in attics. They can be more aggressive and are attracted to incandescent lights. Colonies will die in winter, but queens will overwinter as foundresses to create new colonies the next season. If a nest is not threatening to your activity, leave it alone and let it die off during the winter months. Turn off porch lights at night to deter them from gathering. If a nest is near your home, hirie a pest control specialist to remove it.
Jodie Parolini is agriculture educator for the OSU Cooperative Extension Service in Cherokee County.