Ground-nesting wasps either dig a burrow in the ground or use a burrow left behind by another animal. Some of these wasps are docile, solitary species; the female digs a burrow on her own so that she can lay an egg and leave food behind for her future larvae. Other species are social insects that colonise in the ground and cause trouble for anyone who stumbles upon their nest.
Digger wasps (Scolia dubia) are less than three-quarters of an inch long and have dark blue wings. These wasps are considered beneficial because they parasitise the grubs of the green June beetle, which are considered a pest. The female wasps flies low over the soil looking for grubs. When it catches one, the wasp paralyses the grub, digs a burrow, and then lays an egg inside the grub. When the egg hatches, it feeds off the grub while developing. The adult digger wasp feeds on nectar and pollen.
Sphecius speciousus is a burrowing species of wasp better known as the cicada killer. They look like yellowjackets, being black with yellow markings, and are about 2 inches. A female cicada killer surrounds her burrow with a soil mound, and groups of burrows are common. After the wasp spends a few weeks digging burrows, which can be 6 to 10 inches deep, she hunts cicadas and brings at least one to each burrow before laying an egg and sealing the burrow. Despite their size and their name, cicada killers are not aggressive and typically do not bother people; the adults eat flower nectar and only kill cicadas for their larvae.
The western yellowjacket, Vespula pennsylvanica, is a social ground-nesting species that commonly nests in rodent burrows. They can also build nests in hollow logs, attics and the space inside a house's wall. Unlike cicada killers, western yellowjackets are a social ground-nesting species; their nests contain 500 to 5,000 workers. They aggressively defend their nest if disturbed and can sting multiple times. Western yellowjackets can be a nuisance, especially in the late summer when food supplies are low and more people tend to be outside.
The tarantula hawk (genus Pepsis) is a blue-black wasp with wings that are either blue-black or bright orange. A female tarantula hawk will seek out a tarantula burrow at night and draw the spider out, then give the spider a paralysing sting. The wasp then drags the spider back to a burrow she's already dug or uses the tarantula's own burrow as a nest. She lays an egg and then seals off the burrow. The tarantula remains paralysed and alive for several months as the eggs hatch and the wasp larvae feed off of it.