Fairy Flies

Meet the smallest insects in the world. The Mymaridae, known also as fairy flies, range from a mere 0.5 to 1.0 mm in length, about half the size of a grain of salt. These minuscule creatures are actually some of the most common chalcid wasps, (not flies) only rarely noticed by humans due to their size. They have a family of around 1400 species, including that of the Dicopomorpha echmepterygis, or the smallest known insect (0.139 mm). In fact, the Dicopomorpha echmepterygis is so minute that it is even smaller than certain cells, even a human neuron, making them almost impossible to see with the naked eye. 

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Their miniaturization means that they are about as small as insects can get. But how can they reach such scaled-down size? First of all, their bodies are a lot simpler than other insects. They have the regular legs and antennas, but those body parts tend to have fewer segments. Their circulatory and respiratory systems need not be as complicated either, since nutrients don’t have as far to go anyway. Fairyflies rely on a diffusion process instead. The smallest species do without blood vessels or even hearts.

However, being small doesn’t come without compromises. Their eyes are so small that they are near the limit of being able to bend and reflect light, and fewer lenses means less clear images. This is why fairy flies mostly use smell to get around. In fact, males of some species have abandoned their eyes altogether including their wings, making them the smallest of the smallest insects. 


Those that do have wings possess little feathery frills around them. These bizarre club-shaped wings probably work because when you are that small the air seems a lot thicker, more like syrup. Rather than fly, they grab on to air a bit like how we would swim through water. Experts think that the frills act as mini paddles, allowing them to have effectively larger wings while sparing weight. They also reduce potential turbulence and drag while in ‘flight’.

These are all ways fairy flies minimize themselves to ultimate conciseness. However, the main way they do this is by having fewer and smaller cells. For instance, some cells super-condense their DNA to shrink their nuclei further. They also squeezed out any extra cytoplasm which means their neurons are at the smallest possible size. The axons of each neuron are as thin as they can be before they stop sending signals altogether. The tiniest species only have 7400 neurons total which is pretty minimal considering the pest fly has about a hundred thousand of them. 


But this alone is not enough to miniaturize their brains so they can fit into their tiny heads. So most neurons have actually jettisoned their nuclei. This means that fairy flies depend on the proteins they made as juveniles to sustain them for the rest of their lives. That may sound like a lot, but in reality they only live for a week. 

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For a final bit of compactness, fairy flies ultimately down-size their reproductive system. Because it takes a lot of energy to grow an embryo, most insects pack their eggs with lots and lots of yolk. But to do that is quite a burden if you are less the size of a grain of salt. So, fairy flies depend on other insect’s eggs to solve the problem. Most of its metamorphosis occurs within the hosts’ egg, with around two to four larval stages. The larvae munch on the host’s egg until it emerges as its full adult form. 


All fairy flies are parasitoids of other insect eggs, meaning that they spend their larval stage on a host, usually ending in the latter’s demise. Parasitoids are different from parasites such as fleas and lice, which do not necessarily kill their host. For this reason fairy flies are used widely as pest controllers. That is only one of the reasons why scientists are studying these fascinating creatures. Their tricks to miniaturize themselves may help us to create tiny computers and develop our technology.

By Jiyoo Kim (Year 9 Student at Bangkok Patana School) 

Works Cited

ESF Office of Communications. “Tinkerbell Fairyfly | 2014 Top 10 Species | ESF Top 10 New Species.” Esf.edu, 2014, www.esf.edu/top10/2014/09.htm. Accessed 6 Aug. 2021.

Polilov, Alexey. “Dicopomorpha Echmepterygis,” Research Gate, 2021, www.researchgate.net/lab/MicroInsectLab-Alexey-Polilov. Accessed 5 Aug. 2021.

SciShow. “These Insects Are Smaller than a Single Cell...How?!” Www.youtube.com, 2 Apr. 2021, www.youtube.com/watch?v=jb5Q-wQh4GI. Accessed 5 Aug. 2021.

Turner, Lucy. “The Smallest Insect (Dicopomorpha Echmepterygis).” AmazingLife.Bio, 22 Apr. 2021, www.amazinglife.bio/post/the-smallest-insect-dicopomorpha-echmepterygis. Accessed 5 Aug. 2021.