Speaking in very general terms, wasps do a lot of good, actually. The term "wasp" is used to describe thousands of species within the order Hymenoptera. These include: the parasitic wasps, like ichneumonids and braconids; hunting wasps, like mud daubers, digger wasps, and spiders wasps; and pollinators like the fig wasps. As a group, wasps provide extraordinarily important ecological services, including pollination, predation, and parasitism. Put simply, without wasps we would be overrun with insect pests, and we would have no Fig Newtons.
I suspect, however, that you weren't thinking about things like fig wasps when you started wondering why we need wasps. You were probably aggravated by the yellowjackets hanging around your garbage cans, or terrified by the huge hornets' nest you just discovered in the shrub near your pool. We take notice of the social wasps because they build visible nests, often close to our own homes, and because they will defend these nests aggressively. How about these stinging social wasps? Do they serve any good purpose?
Paper wasps, hornets, and yellowjackets
all belong to the same family, the Vespidae. These social wasps share the ability to construct their nests of wood fibers
, which are carefully chewed into pulp by the wasps and molded into paper.
Hornets and paper wasps prey on other insects, and help keep pest insect populations under control. Paper wasps carry caterpillars and leaf beetle larvae back to their nests to feed their growing young. Hornets provision their nests with all manner of live insects to sate the appetites of their developing larvae. It takes a lot of bugs to feed a hungry brood. Both hornets and paper wasps provide vital pest control services.
Researchers at the University of Florence recently discovered another important role of both hornets and paper wasps – they carry yeast cells in their guts! Yeast is used to make bread, beer, and wine, but we know very little about how yeast lives in the wild. The University of Florence researchers found that wasps and hornets feed on late season grapes, which are rich in wild yeast. The yeast survives the winter in the stomachs of hibernating queen wasps, and is passed on to their offspring when the mother wasps regurgitate food for their young. The new generation of wasps carries the yeast back to the next season's grapes. So raise your glass to the wasps and hornets!
Yellowjackets don't get quite as much credit for being beneficial, although they should. Yellowjackets mostly scavenge dead insects to feed their offspring. We do need these services, too, of course. What would the world be like if all the dead bugs just piled up? Unfortunately, their scavenging habits and their love of sugar puts them in close proximity to people, which almost never ends well for the yellowjacket or the person.