Peraion Graufalke
First Post
They yugoloths reimagined for 4e so far haven't been named "yugoloths" or "daemons", but at least once they have been hinted at as being a semi-separate subgroup of fiends with more mercenary behavior and slightly less chaotic behavior. Don't remember which 4e book I read that in . . . .
Mezzoloths have become mezzodemons in MM1 and are described as being very mercenary, which is unusual for demons. No mention of demonic subgroups, though, unless you view the mezzodemons as a subgroup.
Arcanaloths were demons that have been driven out of the Abyss; they (or just their descendants?) have become raavastas in MotP. They lack the "demon" keyword; also no mention of related demons except for a possible kinship with rakshasas.