While dulcet tones might sway humans looking for a partner, it seems they are also important for male mosquitoes: researchers have found the insects chase others only when they hear the buzz of a female.
Male mosquitoes form swarms involving thousands of individuals to attract potential partners, but must avoid bumping into each other while pursuing the females that turn up.
Dr Saumya Gupta of the University of Washington, Seattle, said it was previously thought mosquitoes had such poor vision they could not see each other. What is more, male mosquitoes are known to tune out the sound of other males – meaning they could not rely on their acute hearing to avoid collisions.
Now Gupta and colleagues have shed fresh light on how the insects manage the feat.
“Not only [have] we found [mosquitoes] can see visual cues of other individuals flying around,” said Gupta, “but we found that for males they actually can integrate acoustic cues with visual cues [to find a female]”.
Writing in the journal Current Biology, Gupta and colleagues report how they tethered anopheles mosquitoes within an arena whose walls were covered with an LED panel showing a static pattern of bright pixels. This, they say, mimics aspects of what a mosquito would see in a swarm.
The team then put a large moving blob of light on the LED display to represent another mosquito very nearby.
The researchers found the tethered mosquitoes showed no inclination to steer towards or away from the large blob, although they did change the frequency and amplitude of their wingbeats.
However, when the high-pitched whine of a female was played, males strongly steered in the direction of the blob’s movement.
“As soon as they hear female sounds, they try to intercept the object,” said Gupta. In other words, the sound of a female mosquito appears to trigger a shift in the visual processing of males.
The team also looked at free-flying male mosquitoes, finding they did indeed try to avoid collisions when close to each other in a swarm.
However, rather than steering away to dodge collisions, the insects made other changes in their acceleration – chiming with the results of the earlier experiments.
While malaria is spread by female mosquitoes – as males do not bite – Gupta suggested the study could be used to improve male traps to help control the spread of the disease.
“Mostly females bite and transmit [malaria] after mating,” said Gupta, noting that by trapping males, these processes can be disrupted.
Dr Francesco Baldini from the University of Glasgow, who was not involved in the work, said the results were exciting. “They reveal that mosquitoes respond to visual cues not just based on what they see but also on what they hear.”
Baldini added that the work could help improve the effectiveness of mosquito traps, not only for monitoring specific mosquito species but also, if highly effective, for population control.
“Additionally with growing interest in targeting male mosquitoes, traps designed to lure the non-biting sex could help reduce reproduction rates and ultimately decrease overall mosquito populations,” he said.
However, Dr Lauren Cator of Imperial College London said the most important implication of the study was that it improved our understanding of how mosquitoes used their senses when trying to mate.
“These behaviours are important for the design of control tools such as those relying on the release of sterile males,” she said.
