Have you ever spent an evening outside with the family, lit a bug candle, sprayed your ankles with insect repellant, but still woke up with a few mosquito bites the next morning? A new study is suggesting that those little bloodsuckers have evolved an extremely sharp sense of smell that can pick up different scents easier that originally believed.
Most animals can only process one scent at a time in the olfactory nerves. A smell may feel complex to the brain, but it’s really just individual nerve cells picking up on one odor at a time. Under that guidance, most bug repellants try to mask the human scent — essentially make us invisible to the mosquito.
But scientists now think that the mosquito’s olfactory system is more nuanced than a typical animal. Therefore, repellents that block mosquitoes from detecting human-associated scents could be especially tricky to make. “Maybe instead of trying to mask them from finding us, it would be better to find odorants that mosquitoes don’t like to smell,” said Anandasankar Ray, a neuroscientist at the University of California, Riverside.
Humans don’t necessarily smell like just “humans” — each smell is complex, and mosquitos can sort through the complexity
In America, we’re blessed with a healthcare system that, despite its massive flaws, can easily treat most severe natural illness. Here, mosquito bites are a nuisance; but in many countries, those same insect bites are lethal. In fact, mosquito bites are responsible for more human deaths than any other creature.
Mosquitoes use a variety of cues when “hunting,” including body heat and body odor. The insects smell using their antennae and small appendages close to the mouth. Using three types of sensors in olfactory nerve cells, they can detect chemicals such as carbon dioxide from exhaled breath, or even components of body odor.
Genetic analyses confirmed that some of the olfactory nerve cells had more than one type of sensor. Some cells produced electrical signals in response to several mosquito-attracting chemicals found in humans.
Despite the groundbreaking finds, it’s still unclear why having redundant ways of detecting people’s odors might be useful to the insects.
“Everybody smells slightly differently,” says study coauthor Meg Younger, a neurobiologist at Boston University. “Maybe this is a setup [for the mosquitos] to find a human regardless of what variety of human body odor that human is emitting.”