My green house pest management workers, paper wasps.

Understand these are not Yellow Jackets or hornets which make paper nests that are enclosed in a paper shroud.  These male am open nest of paper cells on a stalk hanging from a sheltered surface usually horizontal but sometimes vertical to accommodate a narrow space.  

Like many wasps they are insectivores. They gather the soft body parts of aphids, thrips, insect eggs and maggots to feed there larva. They are very tolerant of human activity and prefer to use man made structures to shelter their nests.  I have been stung a few times because of putting my hand on a concealed nest or hammering on its location; but they only sting once to warn you. I have successfully moved their nests that were on movable material to more appropriate positions without being stung.

They will not tolerate other wasps in the area therefore I have had no problem with yellow  jackets for the last three years. They apparently steal the eggs and larva from the other wasp nests when the queen has no workers to guard it. Yet they are very tolerant of their own kind. I have five or more nests in a 30 x 20 foot green house with no conflict.  During the first rains this fall some exposed nests melted but the bees from those nests were able to join a larger colony in a sheltered nest.

I have obtained some of those portable garage frames to cover my spring and fall raspberries to protect them from rain spoilage. The paper wasps have now almost completely eliminated the drosaphilia maggot damage and I have only slug and snail damage in my green house.  Need to get the garter snakes interested in moving in.