More tiny flying annoyances!
Stirges get a single magical beast HD, which comes with a rather poor set of ability scores (unless you really like dexterity and don't mind -10 intelligence). They have no natural attacks except for 'attach', which is a touch attack ineffective against tiny or smaller beings that causes them to begin grappling their target with a +12 bonus (for a net grapple check equal to a human fighter).
In addition, every turn they begin attached to someone causes them to deal 1d4 points of constitution damage. However, RAW you're basically forced to end the grapple after four points, meaning that you may very well be wasting half your turns on starting grapples.
Last of all is Weapon Finesse as a bonus feat. It's nice if you somehow get real attacks, I guess.
Between the horrible intelligence, the lack of true natural attacks or opposable thumbs, and the feat tax that will inevitably accompany any caster role, I just can't justify anything but -0 here. Play at your own risk.