Tiny Creatures in Opponents Square

[Felnar]

once a tiny creature moves into the square of a PC, what combat modifiers are used?
like, does the tiny creature get a cover bonus (or some AC bonus) while in another creatures square?
additionaly, how is Stirge combat (tiny grappler) different from combat with other tiny creatures?

i thought there were some kind of modifiers, but didnt find any in the PHB
thanks

 

[robberbaron]

A stirge, when grappling, loses its Dex bonus to AC.

I would have thought that a tiny monster occupying the same square as a PC might get some cover, but I don't know of any written rule about it.

 

[TheGogmagog]

They do not get cover. In the movement section they point out moving through occupied spaces does not grant cover. Also the grapple section does not mention gaining cover for being in a grapple (or pinned). There are also many creatures that use the tactic and there is no mention of cover there.