Asian giant hornets, or “murder hornets” as many came to know them, suffered a setback in their quest to make a new home for themselves in North America when Washington State entomologists found and destroyed a hive full of the massive stinging insects last month.
After closely examining the nest, which was located in a tree hollow, officials say they’ve counted roughly 500 hornets, according to a statement. Some 200 of those individual insects were likely queens, Sven-Erik Spichiger, managing entomologist at the Washington State Department of Agriculture (WSDA), said in a news conference last week.
If Spichiger and his colleagues hadn’t found and eradicated the nest, each of those queens could have flown off into the countryside and started colonies of their own. “It really seems like we got there in the nick of time,” said Spichiger.
Back in May, the U.S. debut of the invasive “murder hornet” strained a national imagination already reeling from a deadly pandemic—it just seemed like too much. The hornets sport a quarter-inch stinger and kill 30 to 50 people each year in their native Japan. That may sound terrifying, but it’s important to remember that most of these deaths are due to allergic reactions, and that bees and wasps in the U.S. kill an average of 62 people every year already.
The more significant worry about the invasion of the Asian giant hornet comes down to their diet: other insects. These huge hornets primarily target honey bee hives, which they can massacre in a matter of hours, leaving thousands of headless bee corpses in their wake. Their bug-filled diet leads some to worry they could threaten American food production in the Pacific Northwest if they become established.
Over the last few months, entomologists with the WSDA have been frantically trying to trap as many of the hornets as they can so they can attach tracking devices to the insects and follow them back to their nests. Finally, on October 22 Spichiger and his team followed a wayward hornet back to its nest in the woods of Blaine, Washington.
On October 24, a crew dressed in heavy, white protective gear destroyed the nest. The operation began with banging on the tree with a stick while a team member vacuumed as many hornets as they could out of the tree-hollow nest. Then the crew sealed the tree with insulation foam and plastic wrap, which they followed with pumping the tree cavity full of carbon dioxide in hopes of suffocating the remaining members of the colony. Last, contractors felled the tree and cut out the section containing the hive so it could be sent off for detailed analysis.
After a couple weeks of examining the nest, here is what scientists have learned. The hive was 8.3 feet up the tree and measured 8 inches wide and 14 inches long, reports Christina Morales for the New York Times.
The location was unusual, Spichiger said in the news conference. Asian giant hornets usually make their nests underground and when they do colonize trees, it’s usually not so high up.
Surprisingly, many of the hornets were still alive when entomologists cracked it open five days after the nest was taken down. Of the nearly 200 queens they found inside, 76 were still kicking and 108 were still growing inside their sealed hexagonal comb cells, reports Stephanie Pappas for Live Science.
The rest of the colony was made up of 112 female workers, nine male drones, which usually emerge just before the new queens to mate with them, and 190 larvae growing in uncapped cells, per the statement.
As Asian giant hornet nests go, this one is pretty pedestrian. In the news conference, Spichiger said nests in their native range can be around five times this big and are capable of producing up to 800 new queens each year.
Spichiger said it’s impossible to be sure his team got to the nest before any of its queens had mated and set off to find a safe place to hibernate through the winter before emerging to form a new colony in the spring. He added that his team thinks it’s likely there are still other nests out there waiting to be discovered. Per the Times, the WSDA will continue trying to trap hornets through November in hopes of finding and destroying more nests.