Most stick insects look like nondescript twigs, but two newly identified species could have come straight out of a psychedelic painting.

Sven Bradler at the University of Göttingen in Germany and his colleagues re-examined stick insects from Madagascar that had previously been classified as unusual examples of two known species. After analysing the insects’ DNA, the researchers found that the sky-blue males among the specimens belong to a new species, which they name Achrioptera manga. The DNA analysis also helped the team to identify another species of colourful, spiny stick insect from the island, Achrioptera maroloko. Females of this species reach up to 24 centimetres in length — meaning they rank among the world’s biggest known insects.

Why the insects have adopted bright colours is unclear: scientists suspect the flashy attire may be intended to attract mates or act as a deterrent to predators. Many species of poisonous frog use bright colours to scare away predators, and some stick insects might use a similar strategy, the researchers say.