Next will be posted as soon as I finish it :)
 
The first part of my changeling headcanon series! At first I planned it to be all in one deviation, but found that it was just so much information that it’d be uncomfortably long to read. So I tried to split it up, and found that I honestly liked it much more this way :) It’s less cluttered and easier to parse …also I rewrote parts, since I could now add even more information! I am very predictable. =P
 
I drew inspiration from so many places for this headcanon series, I don’t think I can remember all of them. Ants and Honeybees are a huge influence, as well as some from Clownfish, Beetles, Cukoo-birds… many animals. You should also read some other people’s cool headcanons! - Lopoddity’s art about Spike and Thorax (among others), Loryska’s changeling headcanons, Spuds-McFrenzy’s Beautyverse changelings, JayRockin’s Changelings …and many more I’m afraid I don’t remember. Many ideas I have here I got by reading their stuff, so please go check them out! :)
 
Oh, and I tried to do some pseudo-scientific names here - that is, I googled “X in latin” or “X in greek” and mashed them together to form fancy sounding titles. Which, if my understanding of how some actual scientific names were made, isn’t too far from the norm…
 
Evolution
 
Original Changelings
 
Before Discord was born around a million years ago, and started to spread magic, chaos and mutations across the world (You can read more about that here if you want) changelings were pretty much unrecognizable from their modern counterpart. They were about a centimeter long and non-sapient. They also appeared more like typical insects, with six thin legs and a segmented body with head, thorax and abdomen. A hard shell with small, not terribly effective yet functional, wings hidden beneath. They lived in large underground hives, several thousand workers and soldiers with one or more queens.
 
Like most creatures living on Gaia, they did have access to some magic. They controlled it via a second pair of antennae, and it let them alter the perceptions of other insects. Psychic powers, which completely convinced other insects that they were not interacting with a changeling, but rather another one of their own species and hive. It only worked on species with some type of cooperative social structure - some others are perfectly happy with cannibalism - but that still left many insects as targets. The changelings’ survival strategy was to both play thieves and cuckoo-birds; infiltrating bees, wasps, ants etc, to both steal their resources as well as hide their eggs among their clutches. When the changelings hatched as grubs, they were cared for by the host species until they metamorphosed into their adult form and instinctively left to rejoin their own hive.
 
(Entomocuculi Parvus: Insect-cuckoo Small. A few specimens has been found trapped in amber. It is the presumed ancestor of the Entomocuculi Equusidae. Named because it’s the small Entomocuculi)
 
 
Discord’s meddling  
Once Discord appeared, they were one of the unlucky species to be caught up in his curiosity. However, as he was very young he didn’t do much aside from scale them up to about the size of a small dog, just to see what would happen.
 
“They died” is what happend. Their entire internal system was designed to be a fraction of the size, and just completely collapsed. Discord found that he didn’t much like dead creatures, as they are pretty much the anthesis to chaotic. But he wanted giant bugs, just to prove he could do it. He tried a “few” more times, changing several hives worth of workers and applying random mutations to them hoping that something would stick. Once he managed to get a few that didn’t immediately kneel over, he tried similar mutations (he would have copied the exact same mutation, except, you know, chaos) on a few hundred other hives. Satisfied that most of them didn’t seem to die, and that he’d succeeded in his minor goal of amusing himself for the afternoon, he left with a POP.
 
The new changelings were very disoriented, but still tried to act on what their instincts were telling them to do. Set some workers to dig a new hive, set the soldiers to form a meat wall around the queens, set a few workers to go out and gather resources.
 
Of course, there were no insects to infiltrate, no matter how far they looked. They did however find a lot of other animals. Luckily for them, at this point they were pretty much soaked in chaos magic -their own magic, which had previously allowed them to manipulate the minds of bees, was altered and amplified so that it worked on pretty much any creature. Not perfectly; the creature wouldn’t be able to see any details, and wouldn’t be able to describe what they had seen if they could speak, but they would be convinced that the changeling was one of them.
 
Another thing this mutation of their magic caused, was the changelings’ ability to “eat” emotions. Their original magic already gave them psychic and empathic powers; going from modifying creatures’ emotions to absorbing them was a pretty small leap. At this point, their main diet was still actual food, but this newfound source of energy gave them a small, but welcome, boost.
 
So they built their hives, and their workers switched to infiltrating wolves, deer, rabbits -pretty much any animal which lived in social groups. Stealing their food, killing their weak when night fell, and sipping on their emotions as an extra snack.
 
(Scientists argue whether the sized up Entomocuculi Parvus should be considered its own species or not. Few fossils of it has been found, and while its outward appearence is quite similar to its original version, just scaled up, it’s unknown how different it is internally)
 
 
Mimicking animals  
After a while the changelings had evolved to be quite adept at mimicking animals, to the point where they appeared as their chosen target even when viewed by another animal. Unlike their first attempts, when a wolf would see a wolf and a rabbit would see a rabbit, and so on.
 
The closer a changeling’s body is to the appearance they’re trying to mimic, the easier it is for them to fool other creatures’ minds into believing their illusion. Since they were currently targeting several different animals, their bodies looked quite generic, but still changed to be less insect-like. Their second pair of legs were becoming less and less used as they pulled them close to their bodies to appear more quadruped, and their second pair of antennae was looking more and more ear-like. Their large initial dose of chaos magic and subsequent alterations really sped up their mutation-rate, which made these changes very rapid (on an evolutionary scale that is).
 
They also grew more intelligent; the more intelligent they were, the better they were at controlling their stronger magic, which in turn lead to their increased chance of survival. Natural selection basically favoured intelligence among the changelings.
 
(Entomocuculi Mutatio: Insect-cuckoo Change. The oldest fossil found of an Entomocuculi that definitely isn’t a sized up Entomocuculi Parvus. Named for their changed appearance compared to Entomocuculi Parvus)
 
That is, until some of them started to come across pony settlements. Or rather, horse settlements, ponies did not exist yet. They quickly found that the emotions of a sapient species were much stronger and gave much more energy. Luckily, the horses had very strong herd-instincts, and would happily dote on and shower with affection any cute, fluffy creature that was vaguely friend-shaped. Like bunnies. Or changelings which was altering their minds to make the horses think they’re bunnies.
 
 
Mimicking horses  
With more energy available from just emotions, the changelings started to slowly shift from being omnivores that supplemented emotions into their diet, to being emotivores that needed to eat just a little food. Their intelligence also continued to grow over time, until they eventually reached what by modern Equestria’s standard would classify them as a sapient species -they were about as intelligent as a ten year old foal, but that’s still…uh… ten year old foals are sapient, is what I’m saying. And it was at this point they started to actually pretend to be foals as well. The love a horse will give to a pet is nothing compared to an orphan foal they come across.
 
Once again, the more similar a changeling is to whatever they’re trying to mimic, the easier it is to maintain. So as they switched to a diet of almost only horse/pony love, they started to change to appear more and more horse-like. Their second set of legs grew even smaller and vestigial, while their neck grew longer. Their abdomen grew thinner to look more tail-like, as some of its functions moved into the thorax. Unicorns existed at this point, so their antennae grew to more resemble one of their horns. Their legs also grew thicker and more pony-esque in appearance.
 
It is worth mentioning that ponies/horses were not the only sapient species Entomocuculi Mutatio encountered -but since this is tracking the evolution of Entomocuculi Equusidae, the branches of this tree which resulted from Mutatio which focused on other species will not be discussed.
 
(Entomocuculi Comminuo: Insect-cuckoo break-into-small-pieces/split. A species which descended from Entomocuculi Mutatio that focused on preying on equines. Named because its thought to be the first species of Entomocuculi which had other distinct sister species alive at the same time, such as Entomocuculi Avis, which didn’t die off)
 
They continued to mimic ponies, and continued to grow to resemble them even more. Their second pair of legs were almost completely gone, and their abdomen were extremely thin and tail-like with a proto-feather like structure under it; almost all the functions had moved into the thorax at this point. Their second pair of antennae looked even more like ears, and their first pair had almost completely fused. Their head-shape now had a very distinct snout, and their mandibles had started to move inside the mouth. Their legs became even thicker and more pony like, with their feet starting to become hoof-shaped.
 
They had also grown even more intelligent, and were now on-par with ponies in that regard. They’d switched up their tactic, also pretending to be adult ponies and not just foals, forming fake romantic relationships with ponies. This is also when their control over their magic grew so refined that their strategy of kidnapping ponies and replacing them with a changeling was possible.
 
(Entomocuculi Eculeusidae: Insect-cuckoo foal-form. A species presumed to be descended from Entomocuculi Comminuo. Named for their close, yet not as accurate as later species’, resemblance to ponies; incomplete pony, a foal)
 
 
The current Common Changeling  
Named so by ponies, because they are the species in Entomocuculi which focuses on ponies specifically, and is thus more common for ponies to encounter than the other species in the same genus. The current Entomocuculi Equusidae very closely resembles a pony superficially. Their second pair of legs is completely gone, their neck and head is pony-shaped and -sized, with the appropriately shaped and sized eyes, “ears” and “horn”. Their abdomen is just a thin tube, with a membrane-feather-like structure, which is supposed to resemble a tail.
 
Their intelligence has not really increased from Entomocuculi Eculeusidae; then again, neither has ponies’. They have gotten better at mimicking ponies however, but that is mainly because of experience and better tactics rather than an increase in magic or mental prowess.
 
(Entomocuculi Equulidae: Insect-cuckoo equine-form. A current living species in the genus Entomocuculi. Named because of their superficial resemblance to ponies.)
 
More on the common changelings’ biology and social structure will be found in the next part of this headcanon series.