Contrary to what many believe, the main food of mosquitoes is the nectar of flowers. These small dipterans can spend their entire lives without sucking the blood of another animal, and in many cases they do. In fact, male mosquitoes never bite, only females have such annoying behavior.
Underlying this difference in behavior between males and females is a very good reason, and that is that it is the females who lay the eggs.
blood proteins
In order to form and lay eggs, female insects need a large amount of protein. Some get it from the animals they hunt; others, like the sexualized female ants, eat their wings in order to start laying; and others produce the proteins through their own metabolism.
There are about 3,500 known species of mosquitoes in the world, and of these, only 200 are hematophagous, that is, they use the blood of other living beings to produce their eggs. To obtain this precious fluid, they stick the stylets that make up their oral apparatus, similar to a hypodermic needle, into the skin of their prey, and suck, while introducing their own saliva, rich in heparin, an anticoagulant substance that helps clots do not form in the fine lumen of the stylet.
drinking human blood
Among the hematophagous mosquitoes there are very few species considered dangerous for humans: the tiger mosquito ( Aedes albopictus ), the yellow fever mosquito ( Aedes aegypti ), the genus Anopheles and the common mosquito, Culex pipiens .
Some are carriers of pathogens, which they get from a sick person, travel in their saliva and inject them into a healthy person through the bite, causing infectious diseases. Examples of this type of pathology are malaria , caused by the Plasmodium falciparum plasmodium and transmitted by the Anopheles gambiae mosquito, or dengue or Zika viruses, transmitted by Aedes albopictus .
attracting mosquitoes
Hematophagous mosquitoes that feed on human blood have a series of adaptations that allow them to find prey in an extraordinarily efficient way. One of the most important factors, which is what indicates to a mosquito that there is a person, is CO₂. In fact, it is carbon dioxide, in combination with temperature, the most relevant factor for a mosquito to end up landing. But in addition, there are other factors that also have a certain weight in the decisions of the mosquitoes.
Some people are regular victims of merciless mosquitoes every summer, while others are lucky enough to be able to count their bites as anecdotal. The truth is that the reasons for the preferences of mosquitoes for some people and not for others are not exactly known. The myth of “sweet blood” is just that, a myth, which seems to have more to do with smells. Our body emits a large number of attractive substances for mosquitoes: sweat, breath, urine or feces, although the most important are those emitted by bacteria on the skin —responsible for the odor of the armpits or feet, for example-.
It has also been found that Aedes aegypti females show a significant preference for people with blood group 0, although this variable has no effect on the fertility of the eggs. Other attractors are dark or black colors, and humidity.
Contrary to what people think, colors like yellow or orange do not attract mosquitoes. The popular belief may come from a confirmation bias—it is easier to see one mosquito in a yellow T-shirt than ten in a black one—or it may be because these bright colors do attract other insects such as butterflies and moths.
Some chemical substances, very common in certain cosmetic formulations, such as ethanol, limonene and linalool, and other products such as acetone, are also mosquito attractors. Foods that contain vinegar, cheese or honey also generate attractive odors for these animals.
How to repel mosquitoes?
Among the mosquito repellents are many commercial products, which can be found in pharmacies and are highly effective. Citronella extract is also traditionally used, in different presentations, or citronellal, the active ingredient isolated from its essential oil. Both have proven their effectiveness as repellents both in vitro and in the field, although this effectiveness increases when used in relatively closed, small or poorly ventilated spaces, in which the essential oil saturates the air.
References:
Dormont, L. et al. 2021. Mosquito Attractants. Journal of Chemical Ecology, 47(4-5), 351-393. DOI: 10.1007/s10886-021-01261-2
Ha, Y.-R. et al. 2014. Detection of Heparin in the Salivary Gland and Midgut of Aedes togoi. The Korean Journal of Parasitology, 52(2), 183-188. DOI: 10.3347/kjp.2014.52.2.183
Kim, J.-K. et al. 2005. Evaluation of Repellency Effect of Two Natural Aroma Mosquito Repellent Compounds, Citronella and Citronellal*. Entomological Research, 35(2), 117-120. DOI: 10.1111/j.1748-5967.2005.tb00146.x
Prasadini, M. et al. 2019. Blood Feeding Preference of Female Aedes aegypti Mosquitoes for Human Blood Group Types and Its Impact on Their Fecundity: Implications for Vector Control. American Journal of Entomology, 3, 43-48. DOI: 10.11648/j.aje.20190302.13
Rebollar-Téllez, E. A. 2005. Human body odor, mosquito bites and the risk of disease transmission. Folia Entomol. Mex., 44(2), 247-265.
Zhou, Y.-H. et al. 2018. Carbon Dioxide, Odorants, Heat and Visible Cues Affect Wild Mosquito Landing in Open Spaces. Frontiers in Behavioral Neuroscience, 12.
