Anyone read/watch Attack on Titan? Spoilers alert if nobody saw the whole thing.
 

 

 
Bertholdt is the one transform into the Colossal Titan and yet so far he never seen stayed in that form for too long and he can’t turn anytime he want without recharging for a long time than most Human Titan-Shifters. Common theory: energy consumption; larger the form, the more energy used.

I wonder where Ocellus got her giant bug form from.  
If this is a creature ponies never seen before, does that means Changelings seen other creatures they came across ponies never have?
 
Okay, for example. Beast Boy from Teen Titans, he can transform into any animal he seen before, he can also transform into alien animals not native to Earth and never seen before by Humans.

@Ryodraco  
It seems to require specific spells to undo the form (twilight and Chrysalis performed one, though twilight’s was brute force and incapacitated the changeling outright). The stamina drain seems the most likely, though I’d assume the love they gain would be enough to keep them charged while in a pony disguise for casual day-in-day-out interactions.
 
That said, this would further show how powerful Pharynx is and how well trained as a soldier he is when he could take the form of the battle bug when he was very young.
 
It also would explain why Chrysalis undid her disguise at the Canterlot wedding; so that she could use 100% of her power in combat.

@Daneasaur  
That is a good idea, my theory had been that a strong hit would force them to change back within a few seconds, but what we saw Ocellus do does suggest fatigue or a time limit may be the real limitation.

God, I hate insectoids from Xenoblade. DX

@Blissey1  
Right, hence why Pharynx couldn’t keep up his bug monster form for long against the Dread Malwurf. Heck, Thorax’s starvation prevented him from keeping his Crystal Hoof disguise.

@Daneasaur  
which has always been my headcanon for it. they can do larger forms, but its exponentially more energy intensive to do so.

@Poison Trail  
Apparently Changelings suffer from fatigue in keeping UP the alternate form, so the larger/more powerful it is, the shorter a time span they can be in it.

I like that they made a new “monster” form for Ocellus rather than just recoloring Pharynx’s. Not sure why. I just do.
 
@Lord Seraph  
Why bother? They were already winning. And once the tide turned they all got blasted away before they had a chance to respond.

@Ryodraco  
No wonder the guards were no match.

-So, chrysalis, can you also transform into a giant bug?  
-No, because I’m not a freak.  
-Ok…

@Lord Seraph  
One possibility is that most changelings can’t take on such large forms. Perhaps there were ones in the invasion who used these forms but we didn’t see them.
 
Most likely real world reason though is that the writers hadn’t come up with this ability for them yet.

Why didn’t they use this form during the Canterlot invasion?

One weakness that seems to exist for these bigger forms is that the changeling turns back after it takes any kind of hard impact.

@Background Pony Number 17
 
Where would have Pharynx gotten the idea, for that matter?
 

 
This makes me wonder how common being able to turn into a giant tank insect is among changelings. Is it something anybug can do with enough training or can only a few talented ‘lings do it? If it’s not based on a real creature, does each changeling have an “innate” form they take when they transform or is it based on personal aesthetic preference?

@Background Pony Number 17  
She could get the idea from a more appropriately sized insect.
 
Maybe she could turn into a giant Flyder.

@PonyPon  
Actually, what worries me more is that creatures like this apparently DO exist in Equestria. Otherwise where would Ocellus get the idea?

@Poison Trail  
Ignorance of his existence.

Rule of Conservation of Mass! At that rate what’s stopping them from turning into Godzilla?

I wish turning into giant bugs that (hopefully) don’t exist was always the changeling’s best trick.

Ocellus OP. Pls nerf. XD