Mostly for my story on how changelings hive work and the social structure.

I have some ideas but I need more to flesh out the setting of which Thorax and Pharynx grew up with.

7376402 Changelings hate each other. The show seems to support this theory. Hate is the opposite of love, and if love = food and they are starving to the point of attempting an all-or-nothing war, then they must hate each other. Otherwise they'd all starve. That's why their social structure - if you could call it that - is so foreign.

It seems likely to me that they are, or were, all very independent (not by choice), and basically all just served their queen for the simple reason that there was no other choice. Nevermind that dissent was punished severely, but there was no reason to dissent. Serving the queen was just what you did, because she provided for them what little they had. Not even directly, necessarily. It's more likely she was simply the mastermind who orchestrated invasion and abductions, etc, etc.

Though to be perfectly honest, I kind of don't like that notion. In the beginning I liked to think that changelings did have a social structure, and actually loved each other quite a lot, and families were big and loving. My previous headcanon being that they shared what little love they had to go around. Love-communism, basically. And they only hated ponies, because they were the source of love. You don't give back something that you need to survive. But now that's not show canon. The reason I liked that a little better is because changelings being hateful mostly-mindless drones very rapidly became an overused trope around these parts. It just seemed like the obvious thing to do with them. The easy answer. Well, the show went and took the easy approach. But, hey, the show creators still did some interesting things with changelings. So I shouldn't complain too much.

My newer headcanon as to why the 'reformed' changelings are all super hyper love-and-tolerate and basically a big hippie commune, is because they'd been deprived of even a basic social structure for basically since the dawn of time (as far as they are concerned). Things that ponies take for granted - family, friends, being able to talk about your feelings, or even talk about anything at all - were something they (mostly) all wanted, and were all secretly envious of the ponies for having. So their natural response to being stuck at one extreme was, of course, to go to the opposite extreme.

7376402
Whenever I encounter something that I don't immediately have a headcanon for, I just steal from bees. Internal anatomy? Bees. Social structures? Bees. Similarly, when I need an incidental character, I use bug species names.

I have two fairly significant headcanons though: First, changeling kings/queens need a member of another species to lay eggs which will hatch into the Monarch caste. All the changelings serve seen have been from Chrysalis's Hive and thus all kinda resemble ponies in base form. As a side effect, this makes Kings much more vulnerable than Queens since Queens can lay (essentially unfertilized) eggs which will hatch into the Worker caste.

Secondly, I have a headcanon that Queens and Kings can use their fangs to permanently change members of other species into changelings. Though, that may be admittedly less helpful in your story. Ultimately, both of those headcanons serve the story they came from, and I think that's where headcanons work best.

7376402
I don't really have headcanon because that changes from story to story.

I did have a story with Equestrian changelings.
For that story, I made them more like people/ponies, and kinda reduced the insect stuff.
Changelings had:

Different factions, Royalty, nobility and others.
Their own language.
Their own religion.

Youngling Chr’Aya looked up at her nurse. “Tell me about the UnderHive again, please Nursey.”

Nursey grimaced. “You shouldn’t be so curious about the UnderHive. There is a place for those that look for knowledge beyond what the Hive teaches. Fanged ch’kals with snapping jaws roam the dark halls for blind changelings with milky white eyes. When you are judged by Bykriss the Just and sent there your eyes turn white. Then you’re stumbling and fumbling through the darkness until a ch’kal finds you. Little one, you don’t want to know what it does to you then.”

Youngling Chr’Aya, just shrugged. “What’s a suicide?”

Nursey just sucked her fangs. “Tchi tchi, little one. So many questions. Suicides are changelings who kill themselves. They go straight to the UnderHive without judgement. There they go to the Floor of Flailing so razor taloned Ekreet can walk on them forever. Can you recite the hells for those who hurt and betray the hive?”

Youngling Chr’Aya stood up on her hind hooves and closed her eyes. “The black sun of madness, the rain of malice, bugbringer winds, the rot of flowers...” When youngling Chr’Aya was done, Nursey gave her a bit of larval honey.

Their naming convention, clan name first, personal name second.
Chrysalis->Chr'Ysalis. Chr’Aya is related to Chrysalis.

Their own funerary customs.

But the story wasn't focused on changelings, so I didn't go in that much detail.
Just enough when needed.

And yeah changelings did feed off of emotions, and love was the best.
But I could imagine some changelings that liked other emotions.

I did write another story, but it had a world that was a mix of Equestria and Earth.
There changelings were accepted members of society.
They still fed off of emotions, but since almost every creature basically radiated them like body heat,
most changelings would be well fed. Some changelings became performers because they could get even more emotions.
Others could work in brothels if they wanted to feast on other emotions.