The Painted Jezebel is common sight around Singapore in both nature reserves and urbanised areas, including the NUS campus (see this post at Butterfly Circle). They are well recognised by the colours on their hindwings, the undersides of which bear bright yellow and red colours.
Sensing danger, most butterflies will fold and hold their wings over their body, exposing their undersides, i.e. ventral wing surfaces, during an attack. It is presumed that these colours advertise a butterfly’s unpleasant taste to predators, deterring attack. However, this has not actually been empirically demonstrated, even though the asgenus is a diverse one, ranging over South Asia and Australia.
Last year undergraduate Jocelyn Wee set out on her honours project with Antónia Monteiro to experimentally test is the colours of Delias hyparete function as aposematic signals.
To do this, Jocelyn constructed artificial paper models with a faithful colour representation of D. hyparete and a grey scale model. She also produced models with single colours intact, grey-scale models or models with no colours. All models were placed simultaneously in the field, with a live mealworm attached. The relative attack rates were measured on 100 models each at three separate field sites – Kent Ridge Road, Tampines Eco-Green and Jurong Eco Garden.
Faithful models of D. hyparete suffered the least amount of attacks, followed by grey-scale models with unaltered red patches, and then by grey-scale models with unaltered yellow patches. They concluded that red and yellow colours function as warning signals.
Next, they mapped dorsal and ventral colouration onto the phylogeny of Delias. This revealed that yellow and red colours appear almost exclusively on the ventral wing surfaces. Basal lineages have mostly yellow, white, and black wings, whereas derived lineages contain red colour in addition to the other colours. Red appears to be, thus, a novel adaptive trait in this lineage of butterflies.
This work was published last week at PLoS as Wee, J. L. Q. & Monteiro, A., 2017. Yellow and the novel aposematic signal, red, protect Delias butterflies from predators. PloS one, 12(1), e0168243.