A research team from the National University of Singapore (NUS) has unraveled the mystery behind the wing colors of the Painted Jezebel, a common butterfly found in urban and forested landscapes throughout the Asia-Pacific region, known for its bright yellow and red wing colors.

While these striking colors have long been presumed to advertise the butterfly's unpleasant taste to predators and deter attacks, their exact function had not been shown. The study, conducted by Miss Jocelyn Wee and Associate Professor Antónia Monteiro from the Department of Biological Sciences at the NUS Faculty of Science, showed that the Painted Jezebel butterfly uses red and yellow colors on their wings as warning signals, with red being a novel and potentially more effective color to members of this lineage of butterflies.

The findings were published in the open access scientific journal PLOS ONE in early 2017.

Red and yellow wings deter predators

To conduct field experiments, Miss Jocelyn Wee, a PhD candidate at the NUS, constructed artificial paper models that displayed the natural resting position of the Painted Jezebel, in which its wings are held vertically over its body. The paper models comprised a faithful color representation of the Painted Jezebel, a grey scale model, as well as models with different color permutations.

The paper models were placed at three sites across Singapore where the Painted Jezebel can be naturally found, namely along Kent Ridge Road, Tampines Eco-Green and Jurong Eco Garden.

Paper models that were faithful color representations of the Painted Jezebel suffered the least amount of attacks. This was followed by grey-scale models with unaltered red patches, and by grey-scale models with unaltered yellow patches.

"The results of our field experiments showed that the red and yellow colors on the ventral wings of the Painted Jezebel serve as warning signals to predators, and demonstrated how predators can play a critical role in affecting the evolution of warning colors within this particular butterfly genus," explained Miss Wee, who carried out the experiments as part of her final-year project when she was doing her undergraduate studies.

The evolution of colors in butterfly wings

The NUS research team followed up on their results by mapping dorsal and ventral coloration onto a phylogeny of the diverse genus Delias, which the Painted Jezebel belong. They observed that yellow and red colors appear almost exclusively on the exposed ventral wing surfaces, and that older lineages have mostly yellow, white and black wing markings, with red appearing as a novel trait in later lineages.

"Our findings demonstrated that red appears to be a novel and potentially more effective protective color to members of this lineage of butterflies," said Assoc Prof Monteiro, who supervised the study. "Such a discovery raises further questions about the possible changes in the underlying genetic networks that would have caused the emergence of red coloration within this speciose genus."

Moving forward, the research team is working to resolve the genetic pathways that underline the evolution of novel wing patterns across different butterfly genera.