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You might say fairies aren’t real, but fairyflies beg to differ.
They’re flying around us all the time,
but they largely go unnoticed thanks to their own kind of magic: miniaturization!
This group includes the smallest insects on the planet!
And scientists are eagerly studying them in the hopes of
learning more of their teeny tiny secrets.
If you haven’t heard of fairyflies, it’s not because they’re rare.
There are around 1400 species of these delicate little wasps.
That’s right, they're wasps, not flies. Poor choice of name.
Anyhow, they live practically everywhere.
It’s just that you don’t see them, because...they’re tiny.
Most species are about a millimeter long.
And the smallest ones are around a sixth or a seventh of a millimeter —
roughly the size of a single-celled paramecium!
What makes this especially mind-blowing is that, as creatures go,
flying insects are actually pretty complex.
They’ve got most of the same organ systems we do.
Plus wings and cute little articulated legs.
That fairyflies can pack all of that into a body
that’s literally microscopic feels supernatural.
Now it’s not, of course — it’s just some extreme adaptation.
In fact, experts think fairyflies may be about as small as insects can get.
And they got some pretty neat tricks to reach such miniscule proportions.
For starters, their bodies are a little simpler than those of their larger kin.
Like, they have most of the normal parts,
but structures like legs and antennae tend to have fewer segments.
Their circulatory and respiratory systems can be a lot simpler too.
Since gases and nutrients don’t have as far to go, fairyflies can rely more
on diffusion. And the smallest species forgo blood vessels and even hearts.
But not everything can be simplified.
In some cases, being small means making compromises.
Take sight, for instance. Since space is so limited on their tiny heads,
they’ve cut down the size and number of facets in their compound eyes.
Each one is now so small that it’s near the limit of what’s physically needed
to bend and absorb light, so it doesn't capture the clearest images.
And fewer of them means they have lower visual acuity than most insects.
So, they rely more on smell to get around.
The males of some species have actually ditched their eyes altogether,
along with other bits of their bodies. Like their wings. And their mouthparts.
Because if you live just a few days, you don’t need to eat!
That gets them down to just one-seventh of a millimeter —
making them the smallest adult insects period.
It’s not just the super-micro males that have ditched wings.
Some whole species do without them, especially ones that
live in windy habitats, like on oceanic islands.
The wings of the ones that do fly are much smaller and cuter than other insect wings.
They’re oar-shaped, with a frill around the edge
that looks like something between a row of eyelashes and a feather.
These bizarre wings likely work because, when you’re that small,
the air feels thicker — more like a fluid.
So experts think those frills act like a paddle,
allowing them to have effectively bigger wings while sparing weight.
They also probably reduce turbulence and drag.
Mostly, though, fairyflies get small by having fewer and littler cells.
For instance, some of their cells super-condense their DNA to shrink their nuclei.
But the nervous system poses a particular challenge.
Fairyflies have already ditched as many neurons as they can.
The tiniest species have just 7400 neurons total—which is already pretty minimal,
when you consider that flies and bees have hundreds of thousands.
But that alone is not enough to make their brains
small enough to fit in their tiny heads.
And they can’t lose any more neurons because the ones remaining
have essential jobs that can’t be eliminated or combined.
I mean, you can’t have just one nerve that does everything.
They also can’t shrink their neurons down any further.
They’ve already squeezed out any extra cytoplasm.
And the long, skinny axons of each neuron are as thin as they can be, because
axons only can get so small before they stop being able to reliably send signals.
So, to get even more compact, they’ve done something kind of drastic:
most of the neurons have jettisoned their space-hogging nuclei.
Yeah, I said nuclei.
They ditch them just before they mature.
And that means the adults rely on the proteins they made as juveniles
to sustain them for the rest of their lives!
Which is only like a week, so it works out.
Fairyflies’ final big miniaturization trick
lets them down-size their reproductive systems.
You see, it takes a lot of energy to grow an embryo.
So most insects make eggs with big, nutritious stores of yolk.
But when you’re tiny, this can be a huge burden. Like, in the smallest beetle,
each egg is more than half the length of the mom’s entire body!
Fairyflies have evolved a macabre solution to this: a parasitic lifestyle!
Well, technically, they are parasitoids, because ultimately they kill their hosts.
They lay their eggs inside the eggs of other insects
so their offspring can mooch nutrients from the other egg’s yolk and eat the embryo.
And that ultimately lets the fairies lay much smaller eggs.
It’s not so great for the other insects, of course. Though, it’s kind of useful to us.
You see, fairyflies parasitize many different hosts, including agricultural pests.
So some are already used by humans as natural forms of pest control!
And further research on them could reveal other useful species.
That’s just one reason scientists are eagerly studying fairyflies.
Others hope that learning more of their tricks for scaled-down living
will ultimately help us understand the lower bounds of multicellular life.
And they could show us how to miniaturize our world.
Like, since their brains pack maximal complexity into a super tiny size,
scientists think they could teach us a lot about brain circuitry,
or even inspire designs for smaller computers!
So the next time someone says they don’t believe in fairies, let them know that
they’ve been around fairies their whole life. They’ve just overlooked them.
Because they’ve been laying their eggs inside of other insect eggs.
Thanks for watching this episode of SciShow! We hope you enjoyed learning about
the magical, miniature world of these real-life fairies.
I definitely did! That’s very weird, they eject the nuclei from their neurons!
If you did enjoy it, I have a feeling that you will also like our episode on
weird phenomena that science can explain. So maybe watch that one next!
Plus, there’s always that little subscribe button
if you need more awesome science in your life in general.
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