Yeerk controlling a morpher; they are killed. The Yeerk?

[Dogman15]

Sorry. That was the only way I could think to summarize this question:

What happens when a Yeerk controlling a morph-capable host morphs into something, and then the host is killed? The Yeerk is still somewhere in Z-Space, controlling the body remotely! How do they die too? I don't get that.

It becomes more infuriating at the very end, when [spoiler]Tom's Yeerk has morphed them into a snake, and Rachel kills Tom (and his Yeerk?) as snake. First of all, this means that the Berensons do not have their son's body to mourn over or bury - just a snake (reminds me of Abron dying as a Taxxon and being buried or cremated on the Andalite homeworld). While Tom dies as a snake, what happened to his Yeerk in Z-Space?[/spoiler] This is what I can't figure out. 

[Chad32]

I don't know. Maybe the Yeerk mind just fades away into nothing. I wouldn't like to think the Yeerk presence would just be there for...how long? Who knows? Seems it could be a fate worse than death.

[DinosaurNothlit]

It might be a little like how the Animorphs got stuck in Z-space in #18.  Most of the time, the Yeerk is unaware of its own presence in Z-space, since it is still connected to the morpher, much like how the Animorphs' minds are connected to their morphs despite also existing in Z-space.  But then when the host dies, the Yeerk loses its connection to normal space, and suffocates (again, like what almost happened to the Animorphs in #18 when their consciousnesses were awakened by a passing ship).

A sucky way to die, for sure.

[TobiasMasonPark]

     He became the Crayak and bent space and time; where he met the Ellimist.

     Seriously though, I was wondering about Yeerks when they die. From what we see in the Capture, once a Yeerk is starved its body sort of...falls out of the ear. But you would think that, once a Yeerk died, the body would just rot away in the hosts head...What, does the Yeerk just give up and leave the head willingly or is it sort of automatic?

[EvilPinkDragon]

If I remember correctly, there was a former controller who went crazy when his yeerk died because it didn't fully leave his brain or something to that effect. So I think it has to leave willingly? Or maybe something went wrong that time? I wish I could remember the book, I think it was one Rachel narrated.

As for the original question, I just always assumed the yeerk would just sort of black out and die because it's still connected to the host's brain. But I think Dinosaur's answer works really well too.

[DinosaurNothlit]

If I remember correctly, there was a former controller who went crazy when his yeerk died because it didn't fully leave his brain or something to that effect.

I believe that was Essam/Hildy Gervais, from Visser.

As for the question of why a Yeerk leaves its host when the Yeerk dies, it's probably an evolved instinct from when they were still infesting Gedds on their home planet.  As is seen in Visser, when a Yeerk dies before leaving the host, a small part of the Yeerk stays behind and drives the host insane.  I'd be willing to bet that the leftover pieces of Yeerk would probably interfere with future infestations, as well, possibly making it impossible for such a host to be fully controlled ever again.  Therefore, it makes evolutionary sense for Yeerks to try and avoid that outcome if they can, as a Yeerk that died while still inside a Gedd host would essentially make that Gedd immune to future infestations, which would be a detriment to the Yeerk species as a whole.  Does that make any sense?

[TobiasMasonPark]

     It makes a lot of sense, actually.

[Gafrash]

The whole fact that a Yeerk morphs WITH the morphing-powered host is a contradiction, to me. I remember upon my first reads it took me some time to question this. For some reason I never really pondered about it when Visser Three morphed, but I think, by the time Jake got infested, I was wondering how it all worked.

It's not like a piece of meat stuck between the teeth like Cassie. It's not like a bullet popping out of the flesh during the morph either. But the Yeerk inside the skull should be treated as a foreign matter in the morphing process. In this process, nothing that belongs to the DNA, say, a bullet, pops out of a wound or, a poison, is purged from the system.

The only way I can see it explaining this is if the Yeerks become literal DNA-extensions to the host via the neuro-connections. It's in tune with the Yeerks assuming the host 100% and a dead-host-is-a-dead-Yeerk thing. In the last moments of death, the Yeerk must break these extensions and Yeerk physionomy automatically works to push itself out.