Mosquitoes are a familiar nuisance during warmer months, often appearing as twilight approaches. A common question arises about their ability to navigate in the absence of light. While it might seem they possess keen night vision, their visual capabilities in dim conditions are actually limited, suggesting they rely on other senses to find hosts.
Mosquito Vision in Low Light
Mosquitoes possess compound eyes, which are different from human eyes. These eyes are composed of numerous small lenses, called ommatidia, that allow them to detect movement across a wide field of view. Unlike human vision, which forms detailed images, a mosquito’s compound eyes perceive outlines and shapes rather than crisp details.
In low-light conditions, their vision is adapted to detect silhouettes, especially against a lighter background like the night sky. While some sources suggest they have “excellent night vision” and can detect objects better than humans in low light, their visual acuity for detailed images remains limited. This means that while they might discern a large, moving shape, their vision is not their primary tool for pinpointing a host in complete darkness.
Finding Hosts Without Sight
Mosquitoes primarily depend on a sophisticated array of non-visual senses to locate humans and animals, especially when light is scarce. One of the most significant attractants is carbon dioxide (CO2), which humans and animals exhale. Mosquitoes possess specialized receptors, called maxillary palps, that can detect CO2 plumes, signaling the presence of a potential host. Once they detect CO2, they navigate by flying back and forth through the plume, moving closer to the source.
Beyond CO2, mosquitoes are drawn to body heat, a clear indicator of a warm-blooded host. They can sense thermal infrared radiation (IR) emitted from skin, which plays a role in guiding them. This infrared detection relies on a heat-activated protein called TRPA1, found in neurons at the tips of their antennae.
Additionally, mosquitoes are attracted to various chemical cues present in human skin odor and sweat. These include lactic acid, produced during exercise, as well as uric acid and ammonia. A combination of carbon dioxide, 2-ketoglutaric acid, and lactic acid creates a particularly attractive scent for female Aedes aegypti mosquitoes.
Nighttime Mosquito Protection
To minimize mosquito bites at night, several protective measures can be employed. Applying insect repellents with common active ingredients can disrupt a mosquito’s ability to locate a host by interfering with their olfactory receptors. These repellents can confuse mosquitoes, preventing them from recognizing human scents.
Wearing appropriate clothing also provides a physical barrier against bites. Loose-fitting, light-colored clothing that covers arms and legs is recommended, as mosquitoes are attracted to dark colors and can bite through tight-fitting fabrics. Mosquito nets, particularly those treated with insecticides, offer an effective physical and chemical barrier, significantly reducing the risk of bites while sleeping. Reducing sources of CO2 and heat around sleeping areas, such as by using fans to disperse cues, can also make you less appealing to these nocturnal insects.