Insects using tools? You heard it right! A recent study has discovered rare evidence of assassin bugs in Australia using plant resin to ensnare and kill their prey. This gluey gum from spinifex grass is used by the crawly critters to catch and keep their unsuspecting victims. While it may sound bizarre, some insects do employ tools, as researchers are now finding more examples of tool use across the animal kingdom. From ants building bridges to beetle babies using poop as a parasite deterrent, the use of tools implies a level of complex cognition, which was once thought to be exclusive to humans.
The Australian assassin bugs belong to the species Gorareduvius from Western Australia's Kimberley region. These bugs are known to collect plant resins, indicating that they use tools more frequently than most insects. Macquarie University biologists Fernando Soley and Marie Herberstein observed 125 of these assassin bugs in wild conditions and in a makeshift lab in a tent. They predicted that if the resin is used as a tool, the bugs covered in resin will be better at catching prey than bugs not covered in resin.
The researchers tested their hypothesis by putting the insects in a glass jar with a stick and two kinds of prey: flies and ants. They wiped the resin off the insects' bodies and repeated the experiment. The results showed that resin-covered insects were 26% more successful at capturing either type of prey than their unarmed counterparts. The bugs even scraped the resin off the spinifex leaves and meticulously applied it to their bodies, especially on their front legs. Even newly hatched and isolated nymphs were found to be coating themselves in resin, suggesting that this behavior is ingrained in the insects. This behavior meets the widely-used definition of tool use, according to the authors. "Assassin bugs manipulated an environmental item (the resin), by taking it out of its usual context and applying it onto their bodies," they write, "Thus gaining a selective advantage through improved prey capture." The use of resin slows down the bug's prey just enough for the assassin bug to grab and kill it.
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The study has been published in Biology Letters. This discovery is significant because it sheds light on the ecological and behavioral conditions that facilitated the evolution of tool use among insects. It also indicates that animals, aside from humans, have advanced cognitive abilities and can use tools to adapt to their environment. So, next time you come across a bug, watch out, it might be carrying a deadly weapon!
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