(hope i'm posting this in the right place)

I understand that if an encounter card says something like "a monster appears", that it typically disappears at the end of the turn. 

Does the same rule apply to monsters that are placed as a result of mythos card? It seems like an awful lot of headlines deposit 2 monsters in different street sections.  I have no idea whether they pop at the end of the turn, or remain on the board.

Any help can be appreciated!

 FuriousG,

You are correct when you say that monsters who appear during encounters do not stay on the board (provided they don't spawn along with a gate; in which case they DO stay on the board  Page #22 Main Rule book).  However, when a mythos card is executed the monsters released into the streets by such cards leave the monsters on the board permanently!  You might be thinking, "that's an awful lot of monsters to deal with!"  This is true, often times investigators find themselves outmatched and outgunned from an early stage in the game.  The fact is that those monsters stay on the board and bother you until you kill them, close a gate with their symbol or have some other event which removes them.

There isn't a FAQ answer (that I know of in regards to this question), but the Mythos process in the main rule book talks about Headlines in the "Activate Mythos Ability" section (pg 12).

"The first player immediately resolves the special text of a headline mythos card.  He then discards the mythos card face down at the bottom of the mythos deck."

FuriousG said:

That's not correct. If an encounter instructs you to have a monster (but not a gate) appearing, the monster appears, then the investigator has to deal with it (fight or flee) and then, in case the monster is evaded or it knocks out the investigator, it's immediately removed from the board, not at the end of the turn. This is quite important in case you have two investigators at the same location and the first one draws the encounter "a monster appears"

As for the Mythos, as FDT has said, monsters spawned via special text of the Mythos card remain on the board.

Hope this helps :-) And feel free to post these questions on the main board, here you should post questions like "how many cards" / "which monster from which set" and so on