The color similarity between certain predatory insects and bombardier beetles traces back to a shared natural threat that shapes their appearance. This observation comes from Kobe University researchers who explored how survival pressures influence look and behavior in these species.
Bombardier beetles possess a remarkable defense mechanism. When bothered, they eject a hot liquid at about 100 degrees toward the attacker. The liquid is produced through a chemical reaction inside the beetle, and a distinctive popping sound accompanies its release. In contrast, some hunting families such as bedbugs and their relatives rely on piercing mouthparts and a simple yet effective approach to capture prey. While visually alike in some cases, these insects are not closely related, indicating that their comparable coloration may arise from parallel ecological pressures rather than shared ancestry.
Shinji Sugiura and his team sought to understand the root cause of this visual convergence. They conducted observations with each insect alongside their natural challenger, the pond frog, in controlled laboratory conditions. The results showed that all frogs rejected bombardier beetles when presented as prey. About three quarters of the time, frogs also rejected other predators, suggesting that bombardier beetles have a stronger defense against frogs than bedbugs do. The researchers noted that some frogs experience discomfort after consumption and may spit out the insects they have swallowed.
In a second set of experiments, the researchers measured how exposure to similar interactions could alter attack rates. Frogs that had previously encountered bedbugs reduced their attacks on the scorers from 75 percent to 21.7 percent. Conversely, prior encounters with bombardier beetles lowered the frog attack rate on bedbugs from 91.3 percent to 40.0 percent. These findings indicate that repeated encounters with similar threats can alter predator behavior, reducing attacks over time.
Overall, the similarity in appearance between these species appears to confer mutual benefits by shaping predator responses and survival strategies across different ecological contexts. The research underscores how predators influence not only prey behavior but also the evolution of conspicuous traits and defense mechanisms in insects.
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