New research led by scientists at the University of Washington, US, indicates that a common mosquito species detects exhaled CO₂ then flies toward specific colours such as red, orange, black and cyan, while ignoring green, purple, blue and white.

The researchers believe these findings help explain how mosquitoes find hosts, since human skin, regardless of overall pigmentation, emits a strong red orange ‘signal’ to their eyes. “Mosquitoes appear to use odours to help them distinguish what is nearby, like a host to bite,” said senior author Professor Jeffrey Riffell. “When they smell specific compounds, like CO₂ from our breath, that scent stimulates the eyes to scan for specific colours and other visual patterns, which are associated with a potential host, and head to them.”

The results, published in Nature Communications, reveal how the mosquito’s sense of smell influences how it responds to visual cues. Knowing which colours attract hungry mosquitoes, and which ones do not, can help design better repellents and traps, said authors.