In the world of flying, stinging insects, Asian giant hornets reign supreme, reaching impressive sizes and wielding mighty venom-filled lances. Now, researchers have found an unlikely hero that can vanquish these buzzing badasses: the humble frog.
As the largest hornet in the world, the Asian giant hornet (Vespa mandarinia) is a true force to be reckoned with. Adults can grow to be up to two inches (50 mm) long with wingspans measuring up to three inches (75 mm) wide. The stingers they are equipped with can be up to about a quarter-inch (6 mm) in length and inject a painful venom – which is stored in large quantities in their abdomens – into their victims. It's also a smooth stinger, which means it can be used again and again unlike the barbed stinger of a honey bee.
These impressive statistics have led people to bestow the dramatic name of "murder hornets" to the insects. Yet, even though the sting can indeed kill some mammals, the hornets are actually not aggressive to humans, with stings rarely leading to more than intense localized pain.
The winged warriors truly earn their title, however, when it comes to honeybees, to which they are an existential threat. The giant hornets feed honey bees to their larvae and use the hive's honey for energy. When a murder hornet scout finds a honey bee hive, it marks it with pheromones, which attracts even more giant hornets. A team of only 15-30 can wipe out a colony of thousands of bees, especially European honeybees, in under three hours.
Frogs to the rescue!
Murder hornets have relatively few natural predators, but new research has revealed that the black-spotted pond frog is one of them. Kobe University ecologist Shinji Sugiura found that this unassuming frog routinely eats the insects, as well as other hornets, including the smaller V. simillima, and V. analis varieties. It was found that the frog was able to withstand not only the hornet's venom, but the physical pain inflicted by the sharp stinger as well, even to the point of having a stinger protrude through its mouth after snatching up the bug.
In tests, Sugiara paired frogs with hornets to match their size. For example, smaller frogs were paired with the smallest V. simillima variety, while the largest frogs were paired with V. mandarinia. He found that the hornets were eaten at a rate of 93% for V. simillima, 87% for V. analis, and 79% for the murder hornets, despite being stung in the mouth or even in the eyes repeatedly.
"While a mouse of similar size can die from a single sting, the frogs showed no noticeable harm even after being stung repeatedly," says Sugiura. "This extraordinary level of resistance to powerful venom makes the discovery both unique and exciting."
While Sugiura doesn't suggest using frogs as beehive sentries, he does say that the findings could have a significant impact on research regarding venom tolerance and pain resistance in vertebrates.
"[The research] raises an important question for future work," he concludes, "namely whether pond frogs have physiological mechanisms such as physical barriers or proteins that block the pain and toxicity of hornet venom, or whether hornet toxins have simply not evolved to be effective in amphibians, which rarely attack hornet colonies."
The work has been published in the journal Ecosphere.
Source: Kobe University
