Spider wasps, family Pompilidae, are common on flowering plants in landscapes. Common species are long-legged, elongate but not slender; and they have dark blue to black transparent wings. Some species have white, orange, red, or blue markings, but the most common in Illinois are all black or bluish black. They range in size from 1 to almost 2 inches long.
These adults feed on flower nectar, making them common on blooming flowers and shrubs. They are unlikely to sting but probably would if handled roughly. On numerous occasions, I have been in their midst engaged in close-up photography and insect collecting without being stung or even seriously bothered.
They are called spider wasps because the adult females collect spiders, sting them, and provision their nests with them. Nests are usually underground but can be in rotten wood or made of mud. Larvae are white and legless. They feed on the paralyzed spiders.
Although intimidating, these wasps are not dangerous. Do not spray blooming plants, to avoid killing important pollinators. If a plant is attracting spider wasps and intimidating people nearby, removing the blooms should cause the spider wasps to leave. Spider wasp burrows are not noticeable and dug in public areas like those of the cicada killer, so burrow treatment is rarely needed.