May 2, 2023 report
Example of tool use by an insect found in Australian assassin bugs
A pair of natural scientists at Macquarie University in Australia, has found an example of tool use by an insect in Australian assassin bugs. In their paper published in the journal Biology Letters, Fernando Soley and Marie Herberstein, describe how they captured wild bug specimens and tested their use of sticky resin as an aid to capturing prey.
Assassin bugs are a large group of bugs that have been clustered together based on similar behavior—the means by which they kill prey. It generally involves poking a hole in prey with a rostrum, pumping in digestive enzymes and then sucking out the internals.
In this new effort, the research pair focused their efforts on assassin bugs of the Gorareduvius genus. They live on blades of spinifex grass—a type of grass that produces a sticky resin. The grass is well known in Australia as it was used by Indigenous people to bind material together when making tools.
Suspecting that the assassin bugs might be using the resin to help them capture prey, the research pair collected 26 specimens and brought them back to their lab tent for testing.
In simply watching the bugs, the researchers noted that both males and females would scrape resin off grass blades and apply it to parts of their bodies—most specifically their forelegs. They next placed individuals in a glass jar after they had had the opportunity to apply resin to themselves.
The research pair then added a single ant and a single housefly to the jar and watched as the assassin bug attempted to capture and eat them. They then repeated the same experiment using the same type of assassin bugs where the resin had been removed using makeup remover. In so doing, they found that the bugs were less effective at capturing their prey.
After testing a number of the bugs, the research team found that they were 26% more successful at capturing their prey when the resin was on their bodies. Conversely, they found that the flies they placed in the jars with the assassin bugs were 64% more likely to escape if the bugs were cleared of resin. In taking a closer look at the action, the researchers found that the resin helped to slow down the prey, making it easier to hold on to long enough for it to be stabbed.
The pair conclude by suggesting that the behavior is a clear use of insect tool use.
More information: Fernando G. Soley et al, Assassin bugs enhance prey capture with a sticky resin, Biology Letters (2023).
Journal information: Biology Letters
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