PARIS: Bright black-and-red butterflies that live on the fringes of the Amazonian rain forest have developed extraordinary techniques of gene-swapping to survive, scientists reported on Wednesday.

Different species of the Heliconius butterfly are sneakily cross-breeding in order to get superior wing colours, according to a comparison of their DNA codes.

Genetic sharing among species, also called hybridisation, is extremely rare in the wild. It usually ends in an evolutionary dead end because the mixed-gene offspring rarely get a survival advantage.

But by sharing traits, two closely-related butterfly species -- Heliconius timareta and Heliconius elevatus -- can swiftly adapt to new or changing habitats.

“What we show is that one butterfly species can gain its protective colour pattern genes ready-made from a different species by interbreeding with it -- a much faster process than having to evolve one’s colour patterns from scratch,” explained researcher Kanchon Dasmahapatra of University College London.

The genomes threw up another surprise.

The delicate antennae of these butterflies have smell receptors, and their tiny feet hold taste buds.

In theory, the butterflies should not be able to smell or taste very well because so much of their genetic treasure is invested in looking good for mating and camouflage.

“Instead, we learned that they have a rich repertoire of genes for olfaction and chemosensation,” Adriana Briscoe of the University of California at Irvine said in a press release.

The study appears in the journal Nature.