by Deidra Wirakusumah, Workshop Designer and Webinar Instructor
To us, insects are small creatures. They are the most diverse group of animals, yet they, more often than not, escape our attention. However, just outside of our ability to see, there exists an entire world of even tinier, microscopic organisms. We are talking about a world, which is ruled, not by insects or other complex organisms, but by single-celled microbe, microscopic organism. It is an intense, and dangerous world where success depends on surviving long enough to grow larger than predators and competitors. It’s a whole different world down there, where the ability of these insects to survive are truly put to the test.
The term "microorganism" include anything living that can be seen under a microscope. "Micro-animal", a group in which microscopic insects are a part, refers to microscopic animals. The difference here is that most organisms that are microorganisms are single-celled, while micro-animals are multicellular, meaning they are made up of many cells. Micro-animals include tardigrades (also known as water bears), nematodes (a group of roundworms), and mites (which are arachnids, not insects), among many many others. From our understanding, there are not so many adult microscopic insects, but they do exist.
A whole world exists beyond what we can see.
Why So Small?
Many insects are already quite small, and microscopic insects take minute sizing to a different level. The primary advantage, and a key to their success as a group, is that larger bodies require larger amounts of resources. A smaller body means less food, less waste, and less energy required. Another advantage of being small, is that you can use space in different ways than would a larger animal. An elephant needs several km^2 of space to roam, while a dust mite can live perfectly happily atop that elephant’s head.
Are There Any Disadvantages?
Yes, as is the case with evolution, there is always a give and take. For insects to take advantage of the microscopic world, they had to simplify the ways in which some of their organs function. In many cases, microscopic insects have had to opt out from having specific organs like the heart, or brain, to perform particular functions. Instead, other parts of the body have to compensate in order to do the same job. Insect compound eyes for example are made up of all those many different “windows” that help insects find light and avoid fast moving objects like predators. Yet you can’t have eyes with as many working parts when you are a fraction of the size of other insects. So microscopic insects have much simpler eyes that use less cells. They help to detect light, but not much else, they need to rely on their other senses.
1. Itty Bitty Babies
The most common microscopic insects do not belong to any specific species, they are just tiny when they are born. Baby insects are always tiny, and for some, they start off really really tiny. For these insects, they are entering a dangerous world. They need to avoid being eaten and find enough food for themselves, all while having less cells than do their larger insect family members. These insects are almost always in a transitional phase, meaning they do not spend their lives at a microscopic size. As long as they eat well and escape predators that might eat them, they will outgrow the microscopic world.
Insects are small. Some insects are smaller. And insect babies are even tinier!
2. That Stings, A Little
The tiniest adult insects title goes to a group of wasps called the fairyflies (a misnomer). With the adult averaging at 0.5-1mm, you would barely notice them, even though they are quite common throughout the tropical and temperate regions. This group of wasps are parasitic, meaning they need to live off of other organisms to survive. In this case, fairyflies often live, develop, and mate, inside the eggs of other insects.
Dicopomorpha echmepterygis, the world’s smallest known insect species, exhibits something called sexual dimorphism, where the males and females have different characteristics (think of how a male peacock is brightly colored while a female peacock is brown and camouflaged). In this case, the male is less than 40% smaller than the female, and has no eyes or wings. For reference, that means while the female is 550µm, the male is only 180µm - that's smaller than many amoebas!
The title of smallest flying insect also goes to a member of the fairyfly group, Kikiki huna, found in Hawai’i at about 170µm. But while these wasps have the ability to fly, their wings look very different from most other wasp wings. Because of their diminutive size, these fairyflies cannot have the full wings that other, larger, wasps have. Instead they have flat, skinny wings which have bristles.
The fairyfly Tinkerbella nana, image by Huber and Noyes, 2013
A very close relative to Kikiki huna, and the second smallest known flying insect is found in Costa Rica. Tinkerbella nana, is also a species of parasitic wasp, and grows to about 230µm, only a little wider than the width of a strand of human hair.
3. Proud and Free
While the tiniest of insects are parasitic, the tiniest free-living, or non parasitic, insects are the Featherwing beetles. Their name comes from the shape of their wings, which, much like the Kikiki huna wings, have long bristles. These wings are very delicate, and these beetles can only fly passively, meaning they open their wings and allow air currents to carry them, as opposed to flapping their wings which would allow them to choose a direction. In this way they travel like a dandelion seed in the wind. The oldest known fossil of this Featherwing beetle was alive to see the dinosaurs during the Cretaceous Period some 99 million years ago. This individual was named “Jason” after the Greek hero and leader of the Argonauts.
Something to note:
As usual with these posts, this list is in no way complete. Remember that these animals are among the tiniest in the world, so an even smaller species could exist and we may never know.
Check It Out!
@my.microscopic.world is an account on instagram that looks at all sorts of critters under the microscope. The author, Martin, even gives tips for finding and photographing these creatures yourself.
Want to Learn More? Check Out Our Sources:
Huber J, Noyes J (2013) A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods. Journal of Hymenoptera Research 32: 17-44. https://doi.org/10.3897/jhr.32.4663