Killing one overwintering mosquito is equivalent to killing thousands of second-generation mosquitoes? It turns out that mosquitoes hide in these places in winter...

"Buzz buzz buzz~buzz buzz buzz", haven't you heard the annoying sound of mosquitoes at night for a long time? In the cold autumn and winter seasons, the number of mosquitoes gradually decreases, and when the weather warms up next year, they come back again.

There is a saying that "killing one overwintering mosquito is equivalent to killing thousands of second-generation mosquitoes". Is this true?

Where do mosquitoes go when winter comes? Do they freeze to death or hide away? Let's talk about this today.

How strong is the reproductive capacity of mosquitoes?

Mosquitoes belong to the family Culicidae in the order Diptera of the class Insecta. There are about 3,000 species, widely distributed throughout the world.

Usually, only female mosquitoes suck blood. They use the heat, sweat and carbon dioxide emitted by the human body as clues to locate and use piercing-sucking mouthparts to suck blood. The mosquito's mouthparts are composed of two serrated needles, two lancets, a salivary tube and an esophageal tube. When they suck blood, they will first use the serrated needles to cut the skin and secrete anesthetic substances to relax the muscles. Then, the lancet will be inserted into the skin to find blood vessels to suck blood.

Mosquitoes mate very quickly, usually within 15 seconds, and usually in the air. Some male mosquitoes will wait next to female mosquitoes before they emerge, and once the female mosquitoes break out of their shells, the male mosquitoes will catch them and mate with them. Other male mosquitoes will use carbon dioxide as a clue to search for females near humans.

Some male mosquitoes will gather together to attract females to join them. When the females fly into the group of males, the male mosquitoes will find the female mosquitoes for mate based on the frequency of their wing vibrations.

After mating, female mosquitoes must suck blood to obtain the protein in the blood to promote the development and maturation of their ovaries. After sucking blood, they will lay eggs in the water. They can lay eggs 6-8 times in their lifetime, 200-300 eggs each time. Two days later, they will hatch into mosquito larvae, which feed on microorganisms and algae in the water. After 4 molts, they will pupate. After 2-4 days, the pupa shell will break, and the buzzing mosquitoes we usually see are born. It only takes 10-12 days to complete a generation.

Where do mosquitoes go in winter?

The living conditions of mosquitoes are closely related to the temperature. The most active temperature of mosquitoes is 28 to 30 degrees. They start to react slowly at around 16 degrees, and they will freeze to death in a few days below zero degrees. Of course, there are some mosquitoes with strong resistance to adversity that are not frozen to death. They will choose to hibernate to preserve their strength. Therefore, every autumn, mosquitoes eat like crazy. How can they hibernate without eating enough?

So in winter, mosquitoes hide around us, such as basements, air-raid shelters, warehouses, greenhouses, pipes, wall cracks, wardrobes, corridors, gutters, under beds, sewers, etc. They hibernate in these places because the outside world is too cold to slow down metabolism, and secrete a substance to produce a large amount of glycerol, so that the water in the body will not freeze due to low temperature and damage cells. Wait until the next spring, they will reappear around us.

In addition to overwintering as adults, mosquitoes can also overwinter as eggs. They lay their eggs in water when winter comes, and these eggs also have the characteristics of diapause.

Killing one overwintering mosquito is equivalent to killing thousands of second-generation mosquitoes?

Overwintering mosquitoes will lay thousands of eggs in the spring of the following year. Studies have shown that the number of overwintering mosquitoes will directly affect the number of mosquitoes in the summer of the following year. In addition, overwintering mosquitoes are less active and more concentrated, which makes it easy to eliminate them. Therefore, eliminating overwintering mosquitoes is the key to mosquito control.

What is the difference between male and female mosquitoes?

Different antennae: The antennae of female mosquitoes are similar to those of duckweed and are sparse. The antennae of male mosquitoes are similar to feathers and have many dense hairs on them.

Different mouthparts: The mouthparts of female mosquitoes are composed of six needles, including two upper jaws, two lower jaws, and one tongue and lip. The mouthparts are longer. The mouthparts of male mosquitoes are thin and short, making it difficult to penetrate human skin.

Different abdomens: The abdomen of female mosquitoes is rounder, flesh-colored, and has obvious patterns, while the abdomen of male mosquitoes is green and has no patterns.

Different diets: Female mosquitoes mainly feed on blood, while male mosquitoes mainly feed on nectar and sap from plants.

However, some male mosquitoes with strong self-esteem will also suck blood, after all, they don't want to embarrass the mosquitoes. Entomologists at the University of California, Davis, found that male mosquitoes will also suck blood, but they will pay a heavy price. Researchers conducted an experiment to feed male mosquitoes water, sucrose solution, and pure blood. The results showed that male mosquitoes that sucked sucrose could survive for a month, while male mosquitoes that sucked pure blood could only survive for 5 days at most, which was the same as the time they lived on water alone.

Why do male mosquitoes die suddenly after sucking blood? In fact, the blood of vertebrates is poison to insects, and only a few insects can suck blood. When insects digest hemoglobin after sucking blood, they produce a toxin called hemoglobin. Only insects with the ability to suck blood will produce a layer of peritrophic membrane on the inner wall of the larvae after sucking blood. It has the functions of preventing tissue damage, controlling the secretion of digestive enzymes, and preventing interference from pathogens, and can also block and degrade hemoglobin. Male mosquitoes do not have this protective membrane, so male mosquitoes may die suddenly after sucking blood because they are poisoned by hemoglobin.

How to repel mosquitoes?

Mosquito-repellent coils

Compared with other uncommon mosquito repellent methods, mosquito coils are the most effective. The active ingredient in mosquito coils is pyrethroid, a highly effective neurotoxin. When mosquitoes come into contact with this drug, it changes the ion channels of their nervous system, causing them to become excited first, then gradually paralyzed, and finally die. It is worth mentioning that mosquito coils are very low in toxicity to the human body, but you should also pay attention to ventilation.

There are many kinds of pyrethroids. The active ingredients of mosquito coils currently used in the market are generally cypermethrin and tetrafluthrin. Some also use pralothrin and metofluthrin. The difference between them lies in the toxicity and efficiency. It is recommended that pregnant women or children use tetrafluthrin, which has a lower toxicity.

Mosquito repellent

The active ingredients of mosquito repellent are DEET, Icaridin, and chlorpyrifos. They work by interfering with the mosquito's olfactory system and blocking the protein that affects the sense of smell. To put it simply, when you spray mosquito repellent, mosquitoes can't find you. So spray it on yourself or the mosquito, not on your clothes.

Safety ranking: Desmoduryl esters > Icaridin > DEET

Effect ranking: DEET > Icaridin > Dimethoate

How to kill mosquitoes in winter?

In winter, you can clean up more extra bottles and cans at home, and change the water of aquatic plants, bonsai, etc. frequently. This can greatly reduce the hiding places for overwintering mosquitoes.

Expert: Zhang Qikai, Chinese Academy of Agricultural Sciences, PhD in Insect Ecology

This article was reviewed by Wu Shengyong, Associate Researcher, Chinese Academy of Agricultural Sciences