Mosquitoes, those familiar buzzing insects, possess a sophisticated sense of smell. This complex system plays a central role in their survival, particularly for female mosquitoes seeking blood meals for reproduction. Their sense of smell allows them to navigate diverse environments and locate hosts, making it a powerful tool in their natural behavior.
The Science of Mosquito Smell
A mosquito’s sense of smell is rooted in specialized structures on their antennae and maxillary palps. These organs are covered with hair-like structures called sensilla, which house dendrites of olfactory receptor neurons (ORNs). Odor molecules enter the sensilla through tiny pores in their outer layer and are transported by odorant-binding proteins to the olfactory receptors.
These olfactory receptor neurons are highly sensitive to specific chemical compounds. For instance, some receptors are specialized in recognizing carbon dioxide (CO2), a gas exhaled by humans and other animals. Other receptors are responsive to volatile organic compounds, such as lactic acid, which is present in sweat. The sensitivity of these receptors allows mosquitoes to detect minute concentrations of these compounds from a distance, guiding them towards potential hosts.
What Attracts Them to Us
Mosquitoes are drawn to humans by scents released from our bodies. Carbon dioxide, exhaled with every breath, acts as a primary long-range attractant, alerting them to a potential host. As they get closer, other human-derived compounds guide them.
Lactic acid, a byproduct of sweat, and ammonia are strong attractants. These compounds, along with other carboxylic acids present on human skin, create an “odor plume” that mosquitoes follow. Individual variations in body chemistry, influenced by factors like skin bacteria and metabolism, can lead to different levels and combinations of these compounds, which explains why some people are more attractive to mosquitoes than others.
Using Smell to Deter Them
Understanding how mosquitoes detect scents has led to deterrence strategies. Many repellents interfere with the mosquito’s olfactory system. Some, like DEET, act as masking agents, blocking olfactory neurons that respond to human odors. This makes it difficult for mosquitoes to detect attractive scents, making a person “invisible” to them.
Another mechanism involves repellents that directly activate mosquito olfactory receptors, causing the mosquito to avoid the treated area. Research is exploring new approaches, such as identifying novel attractants to lure mosquitoes into traps, or developing compounds that can inhibit their CO2 receptors, disrupting their ability to locate hosts. These advancements aim to provide more effective and environmentally friendly ways to manage mosquito populations and reduce disease transmission.