Strong attraction of male mosquitoes (Aedes aegypti) to humans

Female Aedes aegypti mosquitoes integrate multiple sensory cues to locate human hosts for blood meals. While male mosquitoes do not blood feed, male Ae. aegypti swarm around and land on humans in nature. Basrur et al. (2020) generated male Aedes aegypti lacking the fruitless gene and discovered that they gained strong attraction to humans, similar to female mosquitoes. The authors assume that host-seeking is a female-specific trait, which they confirmed through experiments. However, all experiments were performed under confined laboratory conditions which appear to inhibit swarming behavior. We used semi-field experiments to demonstrate robust attraction of male Ae. aegypti to humans. Human-baited traps captured up to 25% of released males within 15 min, whereas control traps without humans as bait failed to capture males. Rapid attraction to humans was further demonstrated through videography. Males swarmed around and landed on human subjects, with no activity recorded in paired unbaited controls. The absence of female Ae. aegypti in these experiments rules out a hypothesis by Basrur et al. (2020) that males are attracted not to the human, but to host-seeking females near humans. Finally, we confirm the lack of male attraction to humans in small laboratory cages, even when using recently field-collected males. Our direct observations of male mosquito attraction to humans refute a key assumption of Basrur et al. (2020) and raise questions around conditions under which fruitless prevents male host-seeking. Male mosquito attraction to humans is likely to be important for mating success in wild populations and its basis should be further explored.