EDIT: Okay, I left it. But I'm still not seeing summon signs. I'm at the the Scorpioness Boss Fight, there's no summon signs outside of her boss door.
There is one summon for this fight but its one of the hidden ones:
Second, You need the Ring of Whispers, sold by Sweet Shalquoir in Majula (aka the Cat). Putting it on will allow you to understand what the Manscorpion is saying.
Thrid, exhaust all dialogue with him.
Fourth, his summoning sign should appear in the antechamber of the bossfight.
Fifth, return to him after you defeated the boss. (If he died during the fight, you may have to rest on a bonefire for him to respawn)
EDIT: Checking the wiki for the correct names, I also found there is a second one in Scholar. But unlocking that is a real hassle (remember the foggy patch of the Woods with the nearly invisible enemies? You would have to clear that out)