Beneficial Wasp?

[babice]

Around noon today, I noticed a wasp just hanging out on a leaf of a tomato plant. I had also noticed one doing this yesterday afternoon on a leaf of a plant out front. They were on leaves in a shady spot of the plant but I can't imagine they were just sitting there trying to get relief from the sun? I left them alone and they paid me no mind. Are these what are called "beneficial wasps"? I'm wondering if they're one of the reasons I haven't seen any tomato hornworms yet (knock on a huge block of wood). I don't believe I've seen wasps just hanging out like that before. I've always seen the ones that make the paper nests in the eaves under overhangs of my house. I saw one the other day that was just milling about the roof of my front porch. Wasn't doing anything in particular like building a nest or anything. Didn't show any aggression toward me. Just seemed to be checking out the roof in an up and down motion...kinda looked like it was looking for nectar but it couldn't have been doing that of course.