🦟 At dusk, male mosquitoes gather in midair and wait. When a female flies into the swarm, they pick her out by the sound of her wings and give chase. Researchers at Nagoya University have found that a single gene, fruitless, shapes the part of the male's ear that makes this possible. Males lacking the male form of the gene stopped swarming and ignored female flight tones altogether.

A courtship that starts with sound

The insect in question is Aedes aegypti, which the World Health Organization names as the primary carrier of dengue. Its wings make two different notes. Females beat theirs at about 450 hertz; males run higher, at about 750 hertz. Scientists have documented for almost a century that males home in on the female tone while females ignore the male buzz.

The mosquito's ear is its antenna. Sound shakes the long, feathery shaft, and an organ at its base, called Johnston's organ, turns that motion into nerve signals. In a male it holds about 15,000 sensory neurons. The male ear also vibrates on its own and can amplify the female's tone, and in normal males the point of peak sensitivity sits right inside the female wingbeat band.

[ref src="https://journals.plos.org/plosbiology/article/figure/image?size=large&id=10.1371/journal.pbio.3004041.g001" alt="Diagram of mosquito mating behavior with male wingbeats at 750 Hz and female wingbeats at 450 Hz, plus flight-tracking and sound-attraction results for normal and mutant males" origin="Source: Loh et al., PLOS Biology (2026), CC BY 4.0"]

Inside the mutant ear

Fruitless is best known from fruit flies, where it helps create differences in behavior between the sexes. Its instructions are spliced differently in males and females, so only males make a working version of its protein, called FruM.

The Nagoya team, working with the University of Iowa, studied male mosquitoes that cannot make FruM. The results were published in PLOS Biology on October 27, 2026 (October 28 in Japan). In cages at dusk, normal males clustered toward the middle. The mutants flew along the edges, the way females do. When the researchers played pure tones, normal males were strongly drawn to sounds around 400 to 500 hertz. The mutants were drawn to none of the frequencies tested.

A laser instrument that measures tiny vibrations found that the mutants' peak sensitivity had drifted to higher pitches, out of the female band. Their ears had also lost the ability to amplify sound by vibrating on their own; treatments that set off this self-oscillation in normal males did nothing in the mutants. Played the same tone at the same volume, the mutants' auditory nerve fired at about one-sixth the strength of a normal male's. Some of the nerve endings that control the amplifier were even arranged the way they are in females.

At the molecular level, the altered genes included several for dynein, a motor protein thought to power the ear's vibration. FruM appears to directly suppress one dynein gene that is usually active in female ears.

The paper stresses that the mutant ears are not deaf. They still show signs of active hearing, and the authors suggest FruM may also shape how the brain processes sound.

In fruit flies, the ears are essentially the same in both sexes, and fruitless is active only sparsely there. In mosquito ears it is switched on across many neurons. The two lineages split about 250 million years ago, and at some point along the way fruitless seems to have picked up a job building a male-specific ear.

The mutants themselves were not new. The lines were made with CRISPR-Cas9 gene editing in 2020 by Leslie Vosshall's lab at Rockefeller University in the United States. That earlier study found that the mutant males failed to mate and, unexpectedly, were drawn to the odor of a human arm. It left open why they could not find females, and the Nagoya group found part of the answer in the ear.

Why a mosquito's ear matters for dengue

WHO's count for 2024 was the highest on record: about 14.4 million reported cases and about 11,200 deaths, with Brazil alone reporting more than 10 million cases. By the agency's estimate, roughly half of humanity now lives with some risk of dengue.

Professor Azusa Kamikouchi, a neuroscientist at Nagoya University, told Kyodo News that targeting this gene might lead to a way to control the insects' breeding. The paper goes a step further in principle, proposing fruitless as a target for genetic control methods built on the mosquito's sex-determination pathway. None of this is a method yet. The researchers say the next steps are to confirm which genes FruM controls directly and to narrow down which ones would make workable targets.

Mosquito control already plays to the male's ear

Traps use the male's attraction to female wingbeats. In 2016, researchers at James Cook University in Australia reported that a pure 484-hertz tone drew 95% of male Aedes aegypti into a trap, a cheap lure for monitoring local populations.

The World Mosquito Program works the other way, releasing mosquitoes rather than catching them. It infects Aedes aegypti with Wolbachia, a bacterium that keeps the dengue virus from multiplying. In a trial in Yogyakarta, Indonesia, published in 2021, dengue cases fell by 77% in treated areas. In 2025 a factory opened in the southern Brazilian city of Curitiba with capacity for as many as 100 million Wolbachia-carrying eggs a week, though AFP reported in May 2026 that it had cut output because orders from the health ministry were lower than expected. The British company Oxitec takes a genetic route: in 2021, its modified males were released in the Florida Keys, and their female offspring do not survive.

Several of these release strategies depend on released mosquitoes mating in the wild, and mating starts with a male finding a female by ear. That makes a gene that sets male hearing both a possible weak point to exploit and a trait that released males need to keep intact. The researchers have not made this link; it is the editors' inference.

In Japan, a different mosquito

In the summer of 2014, Japan confirmed 162 locally acquired dengue cases, centered on the Tokyo area, its first in 69 years. They were carried not by Aedes aegypti but by its close relative, the Asian tiger mosquito, Aedes albopictus. Aedes aegypti is not established in Japan. According to a fiscal 2023 briefing by the National Institute of Infectious Diseases, it once lived in Okinawa but vanished after a last record on Ishigaki Island in 1970, and mosquitoes that arrived on planes were found at airports such as Narita six years in a row through 2017.

Japanese labs are chasing other mosquito-borne diseases too, including a malaria drug candidate that stops the parasite from breaking out of red blood cells (read more).

Where you live, what is being tried against mosquitoes: sound traps, bacteria, modified males, or just a can of repellent?

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