Mm, and in that picture you can see the giant swarm of mosquitoes he was letting out? You have better eyes than me.
See also this. At most it was one. Just opening an empty jar while you have another jar with bugs in it can be an effective stunt.
My boss was at his talk. He did not release the mosquitos. He did have a vial of them there and threatened to, as a joke (boss-man actually said his whole talk was pretty entertaining). So all of you yammering about suing and crap can calm down.