What Is The World's Smallest Insect?

A few days ago I introduced you to the world's largest insects. But how about the world's smallest one? Have you ever wondered how small can an adult insect get? What's the limit? Sure, insects are already small but still.. they are complex, multi-cellular organisms with limbs, head, thorax, abdomen, reproductive organs, antennae and other stuff! So, it's not like they can be as small as.. let's say an amoeba, right? Or maybe not?

Allow me to introduce you to Dicopomorpha echmepterygis, the current record hodler for world's smallest insect. How small? Really, really, really small! So small that we actually need an electron microscope to have a good look at it:

Male Dicopomorpha echmepterygis (CC BY 3.0, credit)

D. echmepterygis is a species of parasitic wasp from the family Mymaridae and like many insects it exhibits strong sexual dimorphism, meaning that it's easy to distinguish the sex of an individual due to the dramatic anatomical differences between the two sexes. In this case, the most distinguishing trait is the size difference, as males have approximately 40 % the body length females do.

To give you some numbers and a better perspective, the average body length of adult males is only 186 μm (0.0186 cm), with 8 measured specimens ranging from 139 to 240 μm, making them the species with the smallest adult specimen we currently know.  

These critters are actually smaller than certain species of Paramecium and amoeba, both single-celled organisms. Of course, being that small comes with certain sacrifices for males. Being blind and wingless are just a few of them as we will later see. As expected, the eggs and larvae of the wasp are even smaller than fully matured specimen.

The species was first described in 1997 by Edward L. Mockford, who at the time was investigating the life cycle of another insect, Echmepteryx hageni. At some point, Edward noticed some small fairyflies in the place where he was keeping his insects and being curious to find where they came from decided to open up some of their eggs. Inside the first egg he found "a fully formed female fairyfly plus 3 minute animals" . He then opened four more eggs, each containing 1 female fairyfly and 1 "minute animal".

With further research, he discovered that those "minute animals" were actually male D. echmepterygis. His research indicates that adult males mate inside the host egg with the female. Some time after sex, females emerge from the egg host through a hole they (probably) dig with their mandibles. Males seem to also come out through the same hole, as Edward found no male bodies in the "hatched" host eggs. Chances are that they emerge attached to the female, as they don't seem to be capable of much movement. This is further supported by that one time he found a dead female with "3 dead males clinging to her".

Like with most creatures I blog about, there's not much else we really know about the species and the published literature is quite limited. For example, the exact distribution range is a mystery, although the E. hageni specimens Edwards collected came from Bell Smith Springs, Pope County, Illinois. 

As for the world's second smallest insect, it's Megaphragma caribea, again a parasitic wasp, measuring just 0.01778 cm long. Again, the published literature is very limited, all I could find is a French paper published in 1993. If google's translation is correct, the species was described by a single specimen, discovered in Guadeloupe. Rumours say @lemouth is proficient in French, maybe he wants to skip those physics posts that I am too stupid to understand and write one about this tiny creature? :D

What's the World's Smallest Animal?

While writing this post at some point I naturally wondered... If an insect can get that small, how small other, simpler animals can get? And to what group would the world's smallest animal belong to? Before actually checking it out, my guess was that it would be some kind of Zooplankton or something.. and guess what.. I got pretty close :D

The record for world's smallest animal belongs to a group of animals known as Myxozoa. Heh, their name is actually quite funny if you know Greek. It's from the Greek words μύξα and ζώον, which translate to booger and animal. I think it's a good description, as they look something like this:

 
A myxozoan, Myxobolus cerebralis (public domain)

Myxozoa is a group of over 1300 aquatic obligatory parasitic cnidarian animal species. For simplicity, let's just say they are small jellyfish, hence they don't have complex structures and organs like other animals do. But still, they are considered animals, as sponges are too ;)

These guys are exceptionally small, with many species never growing larger than 20 µm! I couldn't find which exact species is actually the smallest one, so I will leave you with that piece of info. Feel free to leave a comment if you can come up with a more specific.

The End

True, insects like Phobaeticus serratipes that can get half a meter long are really amazing and exciting:

 Phobaeticus serratipes, one of the world's longest stick insects (CC BB SA 2.0, credit) 

But if you ask me, insects like D. echmepterygis that can fit all those organs and cells and everything in a space the size of an amoeba are equally amazing, if not more! Don't you agree? :)

Lately I am closing my posts with cool animal videos that I have recently watched but today I have something totally different for you. It's a youtuber I discovered yesterday and I instantly fell in love with. Enjoy:

See you tomorrow!

References & Further Reading

 - All references are provided in the form of clickable links in the main body of the post :)