The whine of the mosquito is unpleasant and often inescapable outdoors on summer evenings. Mosquitoes track you down from tens of metres away by sensing carbon dioxide in the air you breathe out. Within seconds, they home in on exposed skin and feast on your blood with an array of specialised needles.
Only female mosquitoes drink blood, which is how they spread deadly diseases like dengue fever and malaria. Males mosquitoes are harmless, mostly feeding on nectar, but our new research confirms they are just as annoying as female mosquitoes.
Our study, published in the Journal of Medical Entomology, dispels a common misconception that male mosquitoes avoid people. In fact, male mosquitoes from at least one common species probably like you just as much as females do but the reason for their fondness and the way they express it are very different.
The backyard and the laboratory
We used a simple experiment to test if male mosquitoes from the species Aedes aegypti, which spreads dengue, seek out people. We released mosquitoes into a large arena, the size of a suburban yard, and had willing subjects sit in a chair as bait. Cameras facing the subjects filmed mosquitoes as they flew nearby. We confirmed that male mosquitoes are indeed attracted to people.
Female mosquitoes are after your blood, but male mosquitoes just want to hang out. In our experiments, male mosquitoes continuously swarmed around people but rarely landed. By contrast, female mosquitoes land, drink their fill and then fly away to rest.
People differ in their attractiveness to female mosquitoes, and this also holds true for male mosquitoes.
Of the two participants in our study, one person was about three times as attractive as the other. The basis of this variation is not fully understood, but the mix of chemicals you emit from your skin is likely to be important.
We also tested mosquito attraction in small cages in the laboratory. In this environment, males showed no apparent interest in people, while female mosquitoes did. This is likely because male mosquitoes can't detect some of the close-range signals that female mosquitoes can.
If they're not after our blood, what do male mosquitoes want?
Why are male mosquitoes interested in people if they can't feed on your blood? We think it's all about finding the females. Since female mosquitoes are often around people, male mosquitoes that have the same inclination should have greater reproductive success.
But more work is needed to understand the how and why. Almost all behavioural research so far has focused on female mosquitoes.
However, there is growing interest in releasing modified male mosquitoes to sterilise female mosquitoes, which gives our research practical applications.
So, not all mosquitoes you see are out for your blood. Some just want you as their wingman, whether you like it or not.
(The Conversation: By Perran Ross, Postdoctoral research fellow, The University of Melbourne)