Shipment Pending - UPS ation of odorants as its guide. Mosquitoes prefer to feed on people with type O blood, an abundance of skin bacteria, and high body heat; they also favor pregnant women. Individuals' attractiveness to mosquitoes has a heritable, genetically controlled component. The multitude of characteristics in a host observed by the mosquito allows it to select a host to feed on. It activates odour and visual search behaviours that it otherwise would not use, when in presence of CO2. In terms of a mosquito's olfactory system, chemical analysis has revealed that people who are highly attractive to mosquitoes produce significantly more carboxylic acids. A human's unique body odour indicates that the target is actually a human host rather than some other living warm-blooded animal (as the presence of CO2 shows). Body odour, composed of volatile organic compounds emitted from the skin of humans, is the most important cue used by mosquitoes. Many of these volatile odor compounds (VOCs) are produced when skin-associated bacteria metabolize components of sweat and sebum, contributing to individual variation in human odour profiles. Variation in skin odour is caused by body weight, hormones, genetic factors, and metabolic or genetic disorders. Infections such as malaria can influence an individual's body odour. People infected by malaria produce relatively large amounts of Plasmodium-induced aldehydes in the skin, creating large cues for mosquitoes as it increases the attractiveness of an odour blend, imitating a "healthy" human odour. Infected individuals produce larger amounts of aldehydes heptanal, octanal, and nonanal. These compounds are detected by mosquito antennae. Thus, people infected with malaria are more prone to mosquito biting. Contributing to a mosquito's ability to activate search behaviours, a mosquito's visual search system includes sensitivity to wavelengths from different colours. Mosquitoes are attracted to longer wavelengths, correlated to the colours of red and orange as seen by humans, and range through the spectrum of human skin tones. In addition, they have a strong att