Western boxelder bugs are known to release strong-smelling chemical compounds "monoterpenes" when grouping together in sunlit patches.
Researchers from Simon Fraser University, Canada have found that these chemicals help to protect the bugs by killing the germs that live on leaves, the BBC Nature reported.
In the past, scientists have theorised that these compounds could act as a defence or play a role in reproduction; attracting mates and repelling competition.
In the new study, Joseph J Schwarz and colleagues found that the chemicals were emitted specifically during sunbathing sessions and did not seem to communicate anything to other bugs.
Instead, the team discovered that the compounds helped to keep the bugs germ-free.
Bugs in the sunshine were observed "grooming"; wiping their feet and legs across the glands that produce the chemicals.
Under a microscope, researchers found that the chemicals engulfed the fungal microbes that thrive on leaf surfaces, altering their cell structure to prevent them from invading the bugs' bodies.
"The resulting synergism of sunlight and bug-produced chemicals to kill pathogens is simply amazing and heretofore was unknown," Schwarz added.
Some animals, including sea slugs and salamanders, have developed symbiotic relationships with plants in order to use sunlight as an energy source.
By accommodating microscopic algae in their own cells the animals can benefit from the plants' energy production.
Schwarz suggested, the discovery that western boxelder bugs are able to use the power of the sun without relying on plants places them in an elite group.
"If western boxelder bugs can convert the suns' solar energy to fuel chemical work without the aid of microbial symbionts this would be a spectacular accomplishment in the animal kingdom," he told BBC Nature.
The study was published in the journal Entomologia Experimentalis et Applicata.
