Many people are familiar with the large nests of certain communal wasp species, like the paper wasp, sometimes encountered in the rafters of old barns or porches. Some types take their shelter aerially, but others frequent burrows, tunnels, rotting bark and other terrestrial hideaways. While it may be difficult to identify a ground-nesting specimen to its species, close inspection of anatomy and behaviour--and a good insect guide--can sometimes point you toward a specific family of wasps.
Look at the wasp's colouration. Many species of yellowjacket -- a collection of wasps in two genera -- nest underground, and may be distinguished by their bold pattern of black and yellow or white stripes, according to the University of California Statewide Integrated Pest Management Program. By contrast, the great golden digger wasp, another ground-nester, is coloured black and orange and in a less-intricate fashion. Other wasps may be not be so strikingly painted, like the predominantly black tiphiid wasps.
Consider the wasp's size. Some scoliid wasps -- commonly seen on lawns in parts of the United States -- are 3/4-inch long. Compare that with the cicada killer, one of the most impressive of the ground-nesting wasps; this solitary hunter may be 2 inches long. Cicada killers, as their name suggests, are formidable predators of cicadas. They will incapacitate their victims -- which are often larger than themselves -- and drag them into their subterranean burrows.
Define the wasp's body shape. Cicada killers and yellowjackets are robust, with thick abdomens and thoraxes. Scoliid and tiphiid wasps are more slender. The burrowing wasp is even more so, with an antlike head and thorax, long legs and a narrow, elongate and bulbous-tipped abdomen.
Watch the wasp's behaviour. Do you see several of the same kind, and do they appear to be regularly interacting? If so, you may be dealing with a communally nesting ground wasp, like a yellowjacket. These familiar wasps may nest in the thousands, and react in coordinated aggression if their home is disturbed. Roughly resembling a honeybee (at least at a distance), yellowjackets are the most likely candidates for beelike insects roving socially over a lawn in late summer or autumn. They remain active well into the fall, and, because some species seek out meat and decaying food at this time of year, this is when they most frequently interact with human beings. Many ground-nesting species, however, are solitary. The great golden digger wasp, for example, will not be seen massing in groups.
While most wasps are not aggressive, many can sting painfully. You should always keep a respectful distance and avoid disturbing the insects or their shelters.