With flying colours

The disparate hues of insects — bright or plain — have answered questions that have long puzzled ecologists. Take the common Jezebel (Delias eucharis), a brightly coloured South Asian butterfly. Predators avoid it, for it is full of toxins, making it unpalatable. Then take the peppered moth (Biston betularia), which, unlike the Jezebel, perfectly matches its woody brown background, helping it hide from predators. Warning colouration and camouflage are two opposite strategies for survival.

An international study, led by ecologists from The University of Melbourne in Australia and Swansea University, U.K., probed why insects adopt one strategy or the other. In an experiment spanning six continents, over 15,000 prey models were exposed to predators that could choose to attack or ignore them.

The prey models were of three types: a classic warning colour of orange and black, a brown that merged with the wooden background, and an atypical and novel but potentially warning colouration of bright blue and black. Each model came with a mealworm reward. The researchers observed whether the predators decide to attack and eat or avoid them. In one instance, it found the Oriental Pied-Hornbill discarding a boldly patterned, foul-smelling moth after holding it in its bill for nearly five minutes.

The size of the predator community has the biggest impact on which colouration strategy is most successful. When predators compete intensely for food, they are more likely to risk attacking prey that might be dangerous or distasteful. Hence, camouflage is most effective in areas with high predation pressure. But camouflaged prey is more visible in bright environments, and attacked more than prey with classic warning colours. This is also the case in places where cryptic or camouflaged prey is abundant, states the study (bit.ly/Insects-Colours), published in Science in September 2025.

Though naturalists have made strides in understanding how prey adopt colouration for survival against predators, the reason why cryptic or warning colouration is adopted has been unclear. This "very impressive study spanning multiple, coordinated experiments" addresses the issue, says Ullasa Kodandaramaiah, a researcher at the Indian Institute of Science Education and Research Thiruvananthapuram.

The Indian work in this experiment was conducted by Viraj Nawge, Arka Pal, Archan Paul, and Sarika Baidya, under the guidance of Krushnamegh Kunte of the National Centre for Biological Sciences, Bengaluru. "It is rare that we gain deep insights into how animals, especially insects that make up a significant proportion of the known species of organisms on Earth, evolve such effective anti-predatory strategies over a broad swathe of habitats," Kunte says.