In a study published in PNAS, the researchers have discovered a remarkable example of tool use in the insect world: The assassin bug (Pahabengkakia piliceps) weaponizes resin from stingless bee nests to trick its prey into attacking at the ideal predation part. The bug chemically "hacks" bee resin to turn colony defenses into a hunting aid, which provides the first comprehensive evidence of an invertebrate predator using tools to exploit the collective defenses of social insects.
The researchers from the China Agricultural University, the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences (CAS) and the Institute of Zoology of CAS observed and documented how predatory bugs manipulate the defensive resin of stingless bees to enhance chemical signals, and how this behavior affects bee defensive responses that the predators can use to their advantage to lure bees into their optimal hunting position.
Stingless bees deposit sticky, pungent resin around their nest entrances to deter intruders. When predators like ants or geckos become stuck, guard bees swarm to immobilize them. But the assassin bug flips this defense on its head. The researchers observed that the assassin bug deliberately collects resin with its fore- and mid legs, coats its legs, and then lures guard bees by amplifying the resin's chemical signals. Rather than repelling the predator, the resin acts as a beacon, drawing bees into striking range.
"This is a sophisticated manipulation of prey behavior," said WANG Zhengwei from XTBG. "The bug doesn't just avoid detection-it actively provokes attacks to create opportunities."
Through controlled field trials, the researchers demonstrated that resin-coated assassin bugs achieved a predation success rate of 75%. This rate was less than 30% for bugs without resin. Crucially, they found that applying resin to non-hunting body parts (e.g., abdomen) also offered relative benefit, confirming that the stickiness of resin was not the key. Chemical analyses further revealed that the bugs' resin handling boosted emissions of volatile compounds, making them irresistible to guard bees.
The use of tools (defensive resin of bees) by predatory bugs to improve their hunting efficiency indicates a link between tool-use behavior and dietary specialization in the animal kingdom. "Our findings suggest that tool use can evolve under intense selective pressure, even in small-brained invertebrates," said WANG.
The bug climbing onto the stingless bee nest tube. (Image by CHEN Zhaoyang)
The bug raises its fore legs at the entrance preparing to prey. (Image by CHEN Zhaoyang)
