Recently! My body suddenly became itchy, red and swollen for no apparent reason. Read this article! (It’s not a mosquito)

Who in my family would understand? While waiting for the bus, I hadn't even seen any mosquitoes, but my arms and legs were already covered with bites. They were red on the first day, swollen on the second day, and itchy and painful for three to five days. Anti-itching medicine didn't work. Could it be that I was bitten by some kind of poisonous mosquito?

The bitten arm. Source: Photographed by the author

Mosquito: I won’t take the blame for this!

If the "swelling" is painful and itchy, and there is an obvious small red dot in the center of the redness and swelling, the culprit may not be a mosquito, but may be a bite by a sesame-sized insect - a midge (měng).

Many netizens from Guangdong and Fujian are also troubled by midges, and some netizens from Zhejiang even call midges a "West Lake specialty."

Netizens troubled by midges. Source: Weibo screenshot

What do midges look like?

Midges are small, two-winged insects that are only 1 to 4 mm long. At first glance, they look like a black sesame seed. They like to live in humid places.

There are blood-sucking and non-blood-sucking midges. There are 4 genera of blood-sucking midges, belonging to 4 genera of 4 subfamilies. They are Leptoconops of Leptoconopinae, Lasiohelea of ​​Forcipomyiinae, Culicoides of Ceratopogoninae, and Austroconops of Austroconopinae. There is no Austroconops distribution in China, but the other 3 genera are distributed.

Like mosquitoes, only females bite, and female midges use their serrated mandibles (mouthparts) to make a small bite in your skin and suck your blood. They will suck the blood of humans as well as other mammals, and some will even suck the blood of other insects, including mosquitoes.

A midge (Culicoides glabrior) Source: Reference [5]

Different blood-sucking midge species have different peak activity periods. The tenebrionids and gnats are diurnal, while the Culicoides mostly suck blood during the dawn and dusk .

Midges are usually active at dawn and dusk, especially in late spring and summer, when they reproduce in large numbers. Even in winter, they do not stop reproducing completely, but only reduce their rate of reproduction. The life cycle of midges is about 4 to 6 weeks, and the life of adults is only 2 to 3 weeks. Their purpose of survival is only to reproduce. Female midges can lay 30 to 100 eggs at a time, and may lay eggs up to 7 times before the end of their lives.

When you are bitten by a midge, you will feel a slight pain, and then you will see a small black dot the size of a sesame seed at the bite site. Before you can see what it is, it suddenly disappears, and you can't see its flight trajectory at all. Of course, if they are not disturbed, they can suck for 2-5 minutes.

A midge that was slapped to death. Source: Photographed by the author

Some midges can transmit diseases such as bluetongue in sheep and horses . In some countries, especially in tropical areas, midges may also transmit parasitic diseases such as filariasis. However, in the United States and Australia, midges have not been found to transmit human diseases.

I can't tell the difference between midges and mosquitoes

In fact, some people often confuse midges with mosquitoes and regard midges as a small mosquito. Although midges look very similar to mosquitoes, they are much smaller in size. Like mosquitoes, some midge larvae also live in polluted, stagnant water and can "share" the same water source with mosquito larvae.

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The most obvious difference between midges and mosquitoes is that midges are only 1 to 4 mm in size, while common mosquitoes are much larger than midges. In addition, they are different in the following aspects:

1. Midges raise their front legs when resting, but adult mosquitoes do not.

2. The wings of a midge do not extend beyond the abdomen, while the wings of a mosquito are slightly longer than the abdomen.

3. Midges have incompletely developed mouthparts. They use sharp scissor-like mouthparts to cut the skin, and then use their mouthparts like straws to suck blood. Mosquitoes have a long needle-like mouthpart that pierces the skin and then sucks blood.

4. Midges form large mating swarms in the evening that may last for several days. Although male mosquitoes may swarm when mating, they are usually located in specific locations and are difficult to see.

5. Midges only live for 2 to 3 weeks, while some species of mosquitoes can live for several months.

Schematic diagram of the head and mouthparts of a female midge. Source: Reference [5]

Midges began sucking blood 100 million years ago

As early as 100 million years ago in the Cretaceous period, midges lived with dinosaurs , and their morphology and behavior were very similar to modern midges. In 2019, scientists discovered some amber fossils of midges in Myanmar, which provided important information about the morphology, habits and other characteristics of these insects during the Middle Cretaceous.

Amber fossil of a midge. Source: Reference [2]

Through these fossils, the researchers proposed a hypothesis that most groups of modern blood-sucking midges evolved in the greenhouse climate of the mid-Cretaceous. Therefore, the presence of these fossils indicates that midges in the mid-Cretaceous, similar to modern midges, already had the characteristics of blood sucking. These findings help us better understand the evolutionary history and ecology of these insects.

What should I do if I am bitten by a midge?

Although midges are only a fraction of the size of mosquitoes, the bites of midges are more painful and itchy than mosquito bites. Like mosquito bites, midge bites usually cause irritation and leave obvious signs:

▲ Clusters of red and swollen spots.

▲There is a small dot in the middle of the bite where the skin is punctured.

▲The reaction can be severe: People who are sensitive to insect bites may experience a burning sensation and develop red welts.

People who are extremely sensitive to bites may develop painful, itchy, fluid-filled blisters.

The author's arm was bitten by a midge on the 1st, 2nd and 3rd day. Source: Photographed by the author

After being bitten by a midge, ordinary mosquito pack anti-itch medicine may not work, and the anti-itching effect is not very good. At this time, you can try to use an ice pack to cool down or use an over-the-counter antihistamine to relieve the severe pain and itching. Constantly scratching the bite may also lead to secondary infection . If you have an allergic reaction to the bite, or the pain and swelling do not go away after a few days, you need to see a doctor in this case.

How to prevent midge bites?

If you want to avoid being bitten by midges, you have to start with the habits of midges.

Midges need places with stagnant water to reproduce and places with high humidity to survive, so try to avoid staying around bus stops or houses with vegetation or stagnant water .

Midges usually like to appear in the early morning or evening, so you should be especially careful during this time period. When going out, it is best to wear long sleeves and long pants to prevent your skin from being exposed .

Midges are small, weak fliers, and do not like to seek blood meals when there is a moderate breeze, so they are generally not present when there is wind outdoors. Fans or other air circulation devices that increase air circulation may also reduce the activity of biting midges indoors .

Insect repellents are generally effective, and sprays containing pyrethroids applied to the skin or clothing usually provide protection against midge bites for several hours .

Midges are so terrible. Is there any way to sterilize midges, like the sterile insect technique, incompatible insect technique or gene editing technology used to eliminate mosquitoes, to control the number of midges? Unfortunately, there is no safe and effective method to effectively control midges.

References

[1] Borkent, ART, and Patrycja Dominiak. "Catalog of the biting midges of the world (Diptera: Ceratopogonidae)." Zootaxa 4787.1 (2020): 1-377.

[2] Szadziewski, Ryszard, et al. "Haematophagous biting midges of the extant genus Culicoides Latreille (Diptera: Ceratopogonidae) evolved during the mid-Cretaceous." Zootaxa 4688.4 (2019): zootaxa-4688.

[3] Mellor, PS, J. Boorman, and M. Baylis. "Culicoides biting midges: their role as arbovirus vectors." Annual review of entomology 45.1 (2000): 307-340.

[4] Carpenter, S., PS Mellor, and SJ Torr. "Control techniques for Culicoides biting midges and their application in the UK and northwestern Palaearctic." Medical and Veterinary Entomology 22.3 (2008): 175-187.

[5] Mullen, Gary R., and C. Steven Murphree. "Biting midges (Ceratopogonidae)." Medical and veterinary entomology. Academic Press, 2019. 213-236.

Planning and production

Author: Denovo Popular Science Writer

Review | Sun Dingwei, Deputy Director of the Institute of Tropical and Chronic Diseases Prevention and Control, Hainan Provincial Center for Disease Control and Prevention

Planning｜Ding Zong

Editor: Yang Yaping