I believe they are good pollinators.
Emerson White wrote:
I believe that most of them are carnivores, only landing on flowers by chance to rest in between flights.
i think you're right - the benefit of having wasps in your garden is not for pollination but for biodiversity and pest control. Some varieties of Wasps target specific pests that will try to wreck your veggies, often in gruesomely effective ways [like laying eggs in the host that in turn hatch and eat it from the inside, out!]
Wasps look like bees, but are generally not covered with fuzzy hairs. As a result, they are much less efficient in pollinating flowers, because pollen is less likely to stick to their bodies and to be moved from flower to flower.
Although the wasp larvae eat insects, the adult wasps feed on nectar from flowers. They are constantly found on flowers, and play a role in the pollination of plants.
Paper wasps are beneficial predators. They do not scavenge on non-living foods as do nuisance yellowjackets but instead prey on caterpillars and other soft-bodied, leaf-feeding insects. Adult paper wasps also feed on nectar, so can be seen foraging on flowers. During summer you'll often find them around your yard's water puddles and ponds.
Dominulus or European Paper Wasp
Polistes dominulus, Vespidae
Before 1981, the dominulus paper wasp was not recorded in North America. In its native region, P. dominulus is the most abundant paper wasp in those countries around the Mediterranean. It is also found in southern Europe, northern Africa, the Middle East, and eastward into China.
A highly successful colonizer, this wasp has rapidly increased its distribution in the United States during the past 20 years. Before the introduction of this new species, the northern paper wasp, Polistes fuscatus , was the most frequently encountered species in and around structures in Pennsylvania.
Casie Becker wrote:t's an old farmhouse trick that I thought was just superstition when my mother suggested it. However, we painted the undersides of all our eaves a sky blue. Sure enough, despite a very high population of many species of wasp we don't have any building nests on our eaves. It's going on four years now, and they try to start them on trim and furniture and garden plants, but none on the eaves. Apparently they think sky blue means it's not solid enough to attach a nest.