Will there be no mosquitoes if you live in a high-rise building? Mosquito: How high can you guess I can fly?

"If you live high enough, there will be no mosquitoes"

I often hear netizens say, "The lower you live, the more mosquitoes there are; the higher you live, the fewer mosquitoes there are; and if you live on a high floor, there are no mosquitoes at all." This seems to be in line with our general perception, but is it really the case?

Rumor analysis:

This statement is not rigorous.

The wind alone can carry mosquitoes to a height of 160 meters. In addition, mosquitoes can also fly to high floors via elevators and stairs. In addition, mosquito eggs are sometimes carried into high-rise buildings. At the same time, it is not only the height that affects the distribution of mosquitoes, but also stagnant water, temperature, etc. In general, the higher the floor, the fewer mosquitoes there are, but if conditions are right, the number of mosquitoes on the middle and high floors may be higher than that on the lower floors.

Research in the countryside and the wild: Mosquitoes can fly up to 160 meters

Mosquitoes have a relatively weak flying ability among insects. In a survey conducted in Emilia-Romagna, Italy, researchers hung mosquito traps at different heights to explore the distribution height of mosquitoes. The results showed that 90% of Culex pipiens did not fly more than 3.45 meters, and 90% of Aedes caspius did not fly more than 1.64 meters.

A study conducted in rural Gambia found that houses raised to three meters above the ground trapped 84% fewer Anopheles gambiae mosquitoes than houses on the ground. The purpose of the study was malaria prevention and control, so they did use "raising the house" as a measure to reduce mosquito bites. In this way, living in a high place to prevent mosquitoes is not groundless.

Anopheles gambiae (malaria mosquito)

But! Yes! Don't rush to declare victory. Because for such a small animal as mosquitoes, "borrowing the east wind" is a more effective means of dispersal than flying by themselves. A study on insect dispersal in Kenya can prove this. Researchers installed sticky nets on balloons and rose to altitudes of 90, 120, and 160 meters respectively, catching 299 mosquitoes. Even at the highest altitude of 160 meters, there were 58 mosquitoes that were blown up by the wind. Among them, the most were Culex, a family notorious for biting people. Scientists concluded that mosquitoes can spread through the wind.

So in theory, mosquitoes can be distributed up to 50 stories high. Staying at a high place can only reduce the chance of being bitten by mosquitoes, but it cannot really prevent mosquitoes from biting you by riding on the wind.

Research based on floors: There may also be many mosquitoes on mid- and high-rise floors

The above research was conducted in villages and the wild. So, what is the actual situation in buildings?

In 2013, someone in Sri Lanka conducted a study on mosquitoes in buildings. They selected several buildings in a residential area and installed mosquito egg-laying traps on the 1st to 7th floors. The density of mosquitoes was determined based on the number of mosquito larvae (mosquito larvae) in the traps. They found that the egg-laying species were mainly Aedes aegypti and some Aedes albopictus, both of which are typical "flower-legged mosquitoes." Although there are fewer mosquitoes on the seventh floor than on the first floor, it does not mean that the higher the floor, the fewer mosquitoes. The average number of mosquito larvae in the traps on the sixth floor was 1.366±0.527, second only to the first floor.

Mosquito larvae | Copyrighted image library, no authorization for reproduction

A study in Malaysia came to similar results. They also used the method of luring mosquitoes to lay eggs and tested the density of mosquitoes in residential buildings. Aedes albopictus reached as high as the 6th floor, while Aedes aegypti could be found all the way to the 10th floor. It is worth noting that the highest mosquito density was on the 6th floor.

The top floor of a general residential building is the sixth floor, and the tenth floor and above are considered high-rise. So the general "high" is not enough to avoid mosquitoes, and you may even "unexpectedly encounter" the densest mosquito swarms.

Floor is not the only factor affecting mosquito distribution

It is worth noting that height is not the only factor that affects the number of mosquitoes. In a study conducted in Sri Lanka, they found that the place with the most mosquitoes was an apartment with a high population density and an open balcony, which mosquitoes could easily fly in. Enclosed and air-conditioned places (where the temperature is not suitable for mosquito breeding) have fewer mosquitoes.

In addition, we might as well open our minds. Do mosquitoes have to come from the ground? Many people know that mosquito larvae need water to survive, but few people know how little water mosquito larvae need (in large rivers and lakes, mosquito larvae have a harder life and may encounter animals that eat them).

In 2018, the Center for Disease Control and Prevention of Jing'an District, Shanghai, conducted a survey on mosquito breeding in residential areas of Jing'an District. Staff members checked all small stagnant water within five meters of the residents' homes to see if there were mosquito larvae in them. They found that the stagnant water with the highest probability of mosquito larvae was flower pot trays (39.44%), followed by idle containers (22.45%), water containers (17.59%), and aquatic plant bonsai (12.35%). They did not find any stagnant water in ditches, which are generally believed to have the most mosquitoes.

It is worth noting that high-rise buildings also provide another breeding environment for mosquitoes, that is, the drainage ditches and reservoirs in the underground parking lots. A study conducted by the Fujian Provincial Health and Epidemic Prevention Station and the Fuzhou City Health Promotion Office in Fuzhou City found 408 stagnant water in the basements of high-rise buildings, 324 of which had mosquito larvae. The most was that a scoop of water (500 ml) could catch 1,065 mosquito larvae of Culex quinquefasciatus. The frequency of mosquito bites in high-rise basements is also very high, ranking second among all surveyed locations, second only to construction sites.

It can be seen that mosquitoes do not have to reproduce on the ground, and because the puddles where mosquito larvae live are too small, you may not even notice where they are. The conclusion is that there may be relatively fewer mosquitoes on high floors compared to on the ground, but you cannot expect to avoid mosquitoes just by living in a high building. High-rise buildings are not forbidden areas for mosquitoes.

Looking in the mirror of rumors

Sometimes there is more than one factor that affects a thing. Some rumors will overemphasize the uniqueness and absoluteness of one reason, exaggerate that factor, and ignore the influence of other factors.

Author: Red Queen Popular Science Creator

Review | Meng Fengxia, researcher at the Institute of Infectious Diseases, Chinese Center for Disease Control and Prevention

Yin Haisheng, Researcher-level Senior Engineer, Shanghai Insect Museum, Chinese Academy of Sciences