Female mosquitoes require a blood meal to produce eggs, and they employ a sophisticated array of cues to locate their hosts. This explains why some individuals are more attractive to them than others, going beyond random chance.
Blood Type and Secretor Status
Mosquitoes exhibit a preference for certain blood types, with scientific studies indicating that individuals with Type O blood are generally more attractive to many mosquito species. Research from 1974 and a more recent 2019 study observed that mosquitoes preferentially fed from Type O blood samples. Conversely, those with Type A blood tend to be less appealing targets, while Type B blood falls into an intermediate range of attractiveness. However, this preference for Type O blood was statistically significant when compared to Type A, but not necessarily to all other blood types in some studies.
Beyond blood type, an individual’s “secretor status” plays a significant role in mosquito attraction. Approximately 80% of the human population are secretors, meaning their bodies secrete ABO blood type antigens into body fluids like sweat. Mosquitoes can detect these secreted antigens on the skin, providing clues about an individual’s blood type. Among secretors, individuals with Type O blood antigens are particularly appealing, making secretor status a more influential factor than blood type alone in some cases.
Other Key Attractants
While blood type and secretor status contribute to attraction, mosquitoes are drawn to other cues humans constantly emit. Carbon dioxide (CO2) exhaled by humans is a primary long-range attractant, detectable from over 50 feet away. Individuals who exhale more CO2, such as larger people, those exercising, or pregnant women, tend to be more attractive. The presence of CO2 can also enhance a mosquito’s detection of other sensory cues.
Body heat is another significant attractant for mosquitoes, as they possess specialized sensors to detect warmth. Lactic acid, a compound produced by muscles during physical activity and excreted through sweat, is a powerful lure for mosquitoes. Other chemicals found in human sweat and skin odor, such as ammonia, uric acid, and certain carboxylic acids, also contribute to a person’s overall attractiveness. The unique combination of compounds produced by skin bacteria further influences an individual’s distinct body odor, making some people more appealing to mosquitoes.
Mosquito Sensory Mechanisms
Mosquitoes employ specialized sensory mechanisms to detect host attractants. Their long antennae are equipped with fine hairs and receptors that pick up chemical signals, including carbon dioxide, humidity changes, and temperature fluctuations. A specialized sensory organ, the maxillary palp, located on the mosquito’s head, is particularly attuned to detecting carbon dioxide for long-range detection.
Female mosquitoes also possess thermoreceptors, or heat sensors, around their mouthparts and on their antennae. These sensors detect the warmth of nearby animals, guiding them toward a blood meal. Olfactory receptors on their antennae and palps detect specific chemical compounds in sweat and skin odors, such as lactic acid and other acidic volatiles. These sophisticated sensory systems allow mosquitoes to effectively navigate their environment and locate hosts.