As a rule, hornets make overground nests, while wasps make theirs underground. However, there is an exception to this rule; the giant ground hornet (Sphecius speciosus), or cicada killer, burrows in the ground to make her nest. These hornets are found across almost all of North America, but are most populous east of the Rocky Mountains.
About the Giant Ground Hornet
Measuring roughly 1 1/2 inches long, giant ground hornets are a fearsome sight to behold. However, they're relatively docile and don't pose much of a threat to humans. Only females are able to sting, but rarely do. Males may get territorial and fly around you, but don't have the capability to sting. They have rust colored heads and thoraxes, and large yellow and black striped abdomens. They're usually seen during early summer, in gardens, forests, fields and parks.
Giant ground hornets only dig burrows to lay their eggs, so before they begin construction they need to mate. Their exact mating ritual is unknown, but males start by attempting to lure females into their territory. If the females are receptive, the males grab them from behind and mating occurs. Males may fertilize several different females during one breeding season.
Once females are fertilized, they'll begin to dig their burrows so they'll have a place to lay their eggs. These burrows can be anywhere between 12 and 50 inches long and are dug by the females alone. They prefer to nest in areas of loose, sandy soil, where they use their front legs to rake out the dirt and their hind legs to it push out behind them. This results in a large mound of soil, making these burrows fairly easy to spot.
Once the burrows are completed, it's time for the females to lay their eggs. They create individual cells for each egg, which are carefully sealed up to provide a safe place for the egg to hatch and the larvae to develop. However, these larvae will need some sustenance if they hope to survive. These hornets aren't called cicada killers for nothing -- they capture between one and four cicadas, depending on their size, and seal them into the cells with the eggs.