World Mosquito Day丨Take it, no thanks! These methods can make mosquitoes "extinct"

Today is a very magical day - " World Mosquito Day ".

There is probably no creature more annoying than mosquitoes.

They make noises and bite you, live in your house, and pay the rent by giving you a few "bags" out of nothing. If you are lucky, you will be slapped to death on the spot? It's your own blood that sheds... After finally making it to winter, mosquitoes have completely disappeared, and we gradually forgot about them until they came to visit us again.

So how do mosquitoes survive the winter? Why do they reproduce so quickly? How can we get rid of them? Let's talk about it today.

Copyright image, no permission to reprint

01

How do mosquitoes survive the winter?

Mosquitoes cannot keep their body temperature constant. If the temperature drops to a certain level, they will stop moving or even die. In order to save themselves and survive the cold winter, mosquitoes have many tricks. Let's take the common Culex pipiens as an example to talk about how mosquitoes survive the winter.

To survive the winter, the first thing to do is to choose a "feng shui treasure land". When Culex pipiens hibernates, they will not come out to suck blood. They will choose warm (not frozen to death), humid (not easy to dry to death), dim (not easy to be discovered) and windproof places . Specifically, houses, garages, cellars and even dog kennels are all good choices for mosquitoes to survive the winter.

Although we don't know what species this unlucky mosquito is, it is in great danger. | Copyright image, no permission to reprint

In addition to choosing a location, Culex pipiens also practices "internal strength". We all know that in winter, when the days are short and the nights are long, and the temperature drops, mosquitoes can also sense the changes in the photoperiod and temperature, and then " doze " and actively store fat, sugars, etc. in their bodies, which is a bit like brown bears and other animals that have to keep eating to gain weight before hibernation. In addition, in late autumn and early winter, the water content in mosquitoes will also decrease , which helps them survive low temperatures.

Even so, since the eggs, larvae, and pupae of Culex pipiens all live in water and have relatively weak resistance to cold, once ice forms, they will all be wiped out (which is great news for humans), so the vast majority of those that can survive the cold winter are adult Culex pipiens.

Some mosquitoes overwinter similarly to Culex pipiens, while the eggs, larvae and pupae of some mosquitoes are more cold-resistant and do not necessarily have to overwinter as adults .

02

How do mosquitoes reproduce?

We often have a feeling that in summer, there are so many mosquitoes that even with mosquito repellent sprays, screens and mosquito nets, it is still difficult to guard against them.

That’s right, mosquitoes are very fertile. If you think about it carefully, you will know that although mosquitoes are very annoying, they have “no sharp claws and fangs, and strong muscles and bones”, and they have no fighting power. To survive in the cruel nature, the only strategy they can use is “I can reproduce anyway, and I lose if you can eat me all”.

In general, a female mosquito can lay hundreds of eggs at a time , and mosquitoes mature very quickly. For example, Culex pipiens takes only about half a month from egg to adult, and less than a week to lay eggs. And like dozens of other mosquito species, Culex pipiens has another trick: self-fertility . Self-fertility means that adult mosquitoes can lay eggs even without sucking blood. In this way, even if female mosquitoes cannot come out to suck blood in winter, they can still produce offspring [1].

It's not just Culex pipiens mosquitoes that lay their eggs in water. Copyrighted image, unauthorized reproduction

For insects like mosquitoes that lay many eggs that mature quickly, if enough of them survive, their numbers will explode in a short period of time as long as the weather turns warmer and conditions become suitable.

If you find mosquitoes and kill them in their hiding places when mosquitoes are more concentrated in winter and when people are weak and malnourished , you will effectively reduce the number of mosquitoes in the spring of next year and achieve twice the result with half the effort. (Although it is too late this summer, we will post this article again in winter to remind you)

It is very important to prevent and control mosquitoes, because if there are too many mosquitoes, people will suffer.

In areas with generally good sanitation and adequate vaccination, people may only find mosquitoes annoying, with occasional outbreaks of mosquito-borne diseases. But in underdeveloped tropical areas where mosquitoes are truly rampant, mosquitoes are the real death knell. Statistically, mosquitoes easily eclipse any beast on the list of human killers.

Malaria-infected red blood cells | Copyright image, no permission to reproduce

It is estimated that mosquito-borne diseases such as malaria and dengue fever kill 700,000 people worldwide each year . Malaria alone infected 280 million people in 2018, killing 410,000 people.

It can be seen that it is really necessary to prevent and control mosquitoes.

03

How to keep those annoying mosquitoes away from us?

Mosquitoes keep us awake at night and cause us pain and itchiness. How can we deal with them? Here are some simple methods for your reference (to relieve your anger).

1. Physical elimination

Pia! A hand covered in blood... This is probably the only pleasure mosquitoes can bring us (at our own expense).

However, slapping mosquitoes to death on your body may not be a good idea, because the blood will sizzle and you have to wipe it off. So it is recommended that you use electric mosquito swatters first . On the one hand, electric mosquito swatters have their own static electricity effect, which can slightly absorb mosquitoes to increase the hit rate. On the other hand, the pleasant experience brought by the spark lightning barbecue aroma is far better than slapping them to death with bare hands.

In places where the density of mosquitoes that bite people at night is relatively high, mosquito-killing lamps can be used in combination with other prevention and control methods such as backfilling and clearing stagnant water for better results .

2. Mosquito repellent

Mosquitoes really "hate" certain chemicals, so they can be used to make mosquito repellents.

Common ones include DEET, chlorpyrifos , etc. Mosquito repellent containing these ingredients is more effective. If you go to places with dense mosquitoes, high-concentration DEET products are recommended because the effect is more lasting. It should be noted that high-concentration DEET products will feel sticky when used on the skin.

Which side do you think is coated with DEET? | Photo by Gary Clark

But for young babies, some parents may worry that using mosquito repellent will affect the baby's health. At this time, we should use ↓

3. Physical Defense

Mosquito nets and screens can effectively prevent the invasion of mosquitoes. It should be noted that some aluminum alloy windows will have drainage holes, and small mosquitoes and insects still have the opportunity to fly in. You can buy some mosquito-proof stickers on the drainage holes online, and the holes in the screens should also be repaired with patches in time.

4. Chemical weapons

In addition, the common method of dealing with mosquitoes is to spray insecticides . However, on the one hand, mosquitoes are more likely to develop resistance to pesticides, and on the other hand, because the drugs that can kill mosquitoes may also harm other species, and after large-scale use, it is likely that mosquitoes will have the last laugh... Therefore, we need more precise and brutal (to mosquitoes) weapons.

Copyright image, no permission to reprint

So there is ↓

5. Bio-extinction

It is difficult for us to completely eliminate mosquitoes in one go, and as long as there are some "slippery mosquitoes", mosquitoes can make a comeback. Therefore, many biochemical methods will study how to affect several generations of mosquitoes in one operation.

For example, in Guangzhou, China, Professor Xi Zhiyong used Wolbachia (a bacterium that can infect insects and coexist with them) to infect mosquitoes in large quantities and sterilize them . Some researchers also use technologies such as gene drive to make mosquitoes acquire unfavorable traits or even sterilize them, in order to reduce the number of mosquitoes on a large scale.

But even for the annoying mosquitoes, this method may be a bit too much, and the subsequent effects are difficult to predict, so these ultimate measures have not yet been widely used.

There is also a serious question: do we really have the right to decide the life and death of an entire species, even if it is a mosquito?

Author: Ding Zong

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

References:

[1] Liu Lijuan, Li Yaping. Research progress on the overwintering mechanism of Culex pipiens pallens[J]. Chinese Journal of Vector Biology and Control, 2012.

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