In a forest deep in Yunnan Province, China, a predator waits. It doesn’t stalk or chase. Instead, it holds up its arms like a mime, silent and still, luring its victims into a fatal mistake. And it does so using the bees’ own alarm system against them.
This predator is an assassin bug, a little-known species called Pahabengkakia piliceps. And according to a new study, it’s the latest addition to a growing list of animals that use tools—by harvesting, processing, and deploying sticky resin in a surprisingly sophisticated hunt.
Sticky Legs, Smarter Strategy
Assassin bugs are already infamous among entomologists for their resourceful killing techniques. Some coat their limbs with plant sap to help ensnare prey. But P. piliceps, researchers say, goes a step further: it transforms the resin it collects into bait.
“This stingless bee–specialized assassin bug system offers a valuable model for investigating adaptive evolution and tool-use behaviors,” the authors write.
Stingless bees—despite their name—are not defenseless. They protect their hives by smearing acrid resin around the entrance. It’s a sticky trap that slows intruders, giving the colony time to mount a collective defense. But the assassin bug has turned this strategy on its head.
Instead of avoiding the resin, it scoops it up with its forelegs, smearing the substance onto its limbs like war paint. Then it takes its place near the hive’s entrance, arms raised, poised like a tripwire.
This behavior, the researchers found, tricks the bees’ highly tuned defense system. The modified resin emits stronger chemical signals than untreated blobs. That bouquet of volatile compounds appears to mimic the distress cue of a struggling intruder. Drawn in by the scent, guard bees approach to investigate—and meet their end in the bug’s outstretched limbs.
My Chemical Strategy
“We empirically demonstrate how an invertebrate predator adapts to the colony defense of social insects via tool use behavior,” wrote Zhaoyang Chen and Li Tian, entomologists at China Agricultural University and lead authors of the study.
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The team conducted field experiments, comparing the hunting success of bugs in three conditions: one group applied resin naturally to its fore and mid-legs (the “natural group”); another had resin smeared on its hind legs and abdominal tip by researchers (the “manipulation group”); and a third had no resin at all.
The natural group achieved significantly higher hunting success and predation efficiency than the other two. Even bugs with resin on body parts not used for grabbing had better luck than those with no resin.
But why?
At first, the scientists hypothesized that resin helped the bugs avoid detection by mimicking the bees’ own chemical cues. Yet the data told a different story. Resin-coated bugs were attacked more frequently—not less—than their uncoated peers.
That observation flipped the hypothesis: perhaps the bug was inviting aggression. “Although resin application increases the overall attack frequency,” the authors noted, “the attacks are specifically directed at certain body parts”—namely, the fore and mid-legs, which happen to be the assassin’s ambush zone.
Through chemical analysis, they confirmed that when the bug spreads resin onto its limbs, the emission rate of volatile compounds increases. It becomes a chemical siren call to nearby bees.
The predator, in effect, is broadcasting a fake emergency—and setting a trap.
Turning the Tables
To qualify as tool use, behavior must meet certain criteria: control over a manipulable object, altering the user or another object’s physical properties, and mediating interactions with the environment.
By those standards, P. piliceps checks all the boxes.
“The assassin bug amplifies the chemical signals in the resin by evenly applying it to its raptorial legs,” the authors wrote. “This guides stingless bees to rush toward its optimal hunting position.”
Fernando Soley, a behavioral ecologist at the Western Australia Museum who was not involved in the study, told ScienceNews: “They’re not using the resin as it is.… They’re manipulating it.”
He also noted that this kind of behavior likely springs from deep-seated instinct rather than conscious planning. “They have the impulse to put resin on their front legs” even without bees present, said Soley. “It’s like being born with a skill without knowing what it’s for.”
That’s an insight with broader implications. Researchers have long wondered how complex tool use, like that seen in humans and apes, might have evolved. Perhaps it began with such simple, innate behaviors—gradually refined over evolutionary time.
Indeed, the authors of the new study argue that dietary specialization played a key role. Unlike chimpanzees, who eat termites occasionally, P. piliceps relies almost exclusively on stingless bees for survival and reproduction. That ecological pressure may have shaped the evolution of this resin-based hunting strategy.
The study joins a growing body of research challenging the long-held belief that invertebrates are too simple for sophisticated behavior. From Australian assassin bugs to tool-wielding ants and wasps, it’s becoming clear that nature’s cleverness isn’t confined to big-brained creatures.
This time, the tool is a chemical illusion—crafted from the bees’ own alarm system. And the assassin bug’s mastery of that illusion may hold clues to how the roots of intelligence—and deception—grew across the tree of life.
The findings appeared in the Proceedings of the National Academy of Sciences.