This insect likes to hold blind date meetings right above your head!

Some time ago, chironomids were in the news again. They are always very popular every spring~!

Image source: People's Media

Speaking of chironomids, you may be unfamiliar with their name. But every spring when you walk in the wetlands or by the pond, those small flying insects that linger over your head and don't want to leave are them!

Because of their similar appearance to the notorious Aedes, Anopheles, and Culex mosquitoes, people dislike the midges and even fight against them. In fact, they are "cute little creatures" who never suck blood.

Aedes, Anopheles, Culex Image source: Wikipedia

Chironomid (male) Image source: Wikipedia

Why don't midges suck blood?

Chironomidae is a general term for insects in the Chironomidae family. Chironomidae comes from the Greek word for pantomime or pantomime performer. Their English name is very appropriate, non-biting midges, which means non-biting midges. Chironomidae does not make a buzzing sound when flying, and is very quiet. There are many species of Chironomidae, and their distribution range is very wide, from the Arctic to the Antarctic continent, and the altitude spans from 100 meters to more than 5,000 meters.

Chironomids are holometabolous insects that go through four stages in their life: egg, larva, pupa, and adult. They spend most of their life in water and can only survive for a few days after emerging from their shells. During these days, they have to work hard to find a mate and complete their reproductive tasks before they die.

Chironomid (female) Image source: Wikipedia

So why do mosquitoes suck blood, but midges don't?

First of all, mosquitoes are usually females who suck blood, and they do their best to reproduce. The reason why midges do not suck blood is related to their physiological structure and living habits. Adult midges do not have piercing and sucking mouthparts like mosquitoes (many male mosquitoes do not have them either). Due to the degeneration of their mouthparts, adult midges almost do not eat or drink, and their short life is only for reproduction.

So, the midge just looks uncomfortable, but it doesn’t bite!

The midge flying above your head is actually on a blind date

In spring, when you walk by the water, you may come across a large-scale blind date scene of chironomids, densely packed with them trying hard to find a partner... (dancing on your head)

Scientists call this crazy courtship and mating behavior a mating swarm.

Image source: Tadpole Jun

The nuptial flight of Chironomids usually occurs in the evenings of spring and summer. The chironomid group will choose a "feng shui treasure land" - a place with nuptial flight markers. The so-called markers are areas that can form a strong contrast with the surrounding environment.

In the suburbs, they usually hang around water, leaves, treetops, and even cow dung; in towns, midges hang around buildings. The common characteristics of these places are that they have obvious sharp edges and a certain brightness difference. It seems that midges are also good at creating atmosphere!

In addition, chironomids also prefer those light-colored, movable markers, such as a shiny bald head. Of course, different species of chironomids have different preferences, and some chironomids are attracted to black markers.

In fact, the behavior of "following people" by midges often brings trouble to people. Adult midges fly over people's heads as they move around. If they accidentally get into the eyes, it can affect vision at the least and cause conjunctival inflammation at the worst.

Epidemiological investigations have confirmed that the red naked palp midge (Propsilocerus akamusi) is a strong allergen (antigenic substance that causes allergic reactions) second only to dust mites. Many residents are allergic to it due to contact, making it a triggering factor for asthma and other allergic diseases. There are also large numbers of chironomids that often visit residential areas and food stalls. They sometimes fly into homes and sometimes fall into food, causing discomfort.

Baby chironomids in the fish tank

Chironomid larvae (also known as red worms) are the main group of freshwater benthic animals, participating in the energy flow and material cycle of the aquatic ecosystem, and are rich in nutrients such as protein and fat. Therefore, they have become a high-quality natural feed for carp, crucian carp, salmon, sturgeon, eel and other fish.

In addition, chironomid larvae feed is different from artificial feed. Fish eating artificial feed will leave residual feed in the water. These residues will decompose over time and cause water quality to deteriorate. Therefore, when raising tropical fish, goldfish and other high-end ornamental fish, water pollution should be avoided. Chironomid larvae are the first choice of ideal feed organisms.

"Superior rations", image source: Tadpole Jun

A marine midge with its reproductive segment twisted 180°

The petite chironomids can be found not only in cities, but also on rough seas.

There are 3 subfamilies, 12 genera and about 50 species of pure marine chironomids in the 11 existing and known subfamilies. Because they live in an environment completely different from terrestrial freshwater, they have evolved some unique structures and survival strategies.

In order to cope with the turbulent sea surface and strong sea wind, marine chironomids have evolved unique structures. They have paddle-like modified wings, extended front thighs and hydrophobic claw pads; these structures enable them to glide on the water surface by overcoming the surface tension of water like water striders.

There is a species of marine midge (Pontomyia) that can twist its reproductive segment (the body segment where the reproductive organs are attached) 180°, evolving from the traditional dorsal intercourse to the more advanced "ventral intercourse".

Faced with such a strong ability to adapt, we should accept their existence instead of being annoyed by them. Wearing a mask when going out can not only prevent viruses, but also prevent catkins, willow catkins, and insect catkins from entering your mouth. It really kills two birds with one stone~

References

1. Wang Juncai, Wang Xinhua. Larvae of Chironomids in Northern China[M]. Beijing: China Yanshi Publishing House. 2011.

2. Gullan, PJ; Cranston, PS The insects: an outline of entomology. John Wiley &Sons, 2014.

3. Hashimoto, H. Notes on Pontomyia natans from Sado (Diptera, Chironomidae). Science Reports of the Tokyo Kyoiku Daigaku, 1959. Section B 9: 57–64.

4. Ashe, P., & O'Connor, JP (2012). A World Catalog of Chironomidae (Diptera). Part 2. Orthocladiinae. Dublin: Irish Biogeographical Society.

5. Surgeoner, GA, & BV Helson. (1977). A field evaluation of electrocutors for mosquito control in southern Ontario. Proc. Entomol. Soc. Ontario 108:53–58.

6. Nasci, RS, Harris, CW, & Porter, CK (1983). Failure of an insect electrocuting device to reduce mosquito biting. Mosquito News. 43:180–184.

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Review expert: He Jiale, project officer of WWF Northeast Resident Working Group.

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