Invertebrates
Cicada Killer
Sphecius speciosus · also called eastern cicada killer, cicada hawk, sand hornet
In July, patches of sunny lawn across the eastern United States fill with wasps the size of a thumb, cruising low and fast, sometimes flying straight at anyone who walks past. They look like the most dangerous thing in the garden. They are close to the least.
Overview
Sphecius speciosus is one of the largest wasps in North America, the female about 4 cm long, rusty and black with yellow bands. Adults drink nectar; the larvae eat cicadas. It is a solitary wasp — each female digs her own burrow in sandy soil, with no colony to defend.
Paralysed groceries
The female catches a cicada in a tree, stings it to paralyse but not kill it, and hauls the heavy, still-living insect back to her burrow, stocking each chamber with one to three cicadas and an egg. The larva eats the fresh, immobile prey over about two weeks.
All bluff
The males cannot sting at all but aggressively buzz anything entering their territory, including people. The females can sting but almost never do unless grabbed or stepped on. It also sets its offspring’s sex by how much prey a chamber gets.
Status
Not Evaluated but common across the eastern and central US, and usually treated as a minor lawn nuisance rather than a threat.
Cicada Killer: common questions
Is a cicada killer dangerous to people?
Very little. The males, which are the ones that dart aggressively at people walking near a nesting area, have no sting and cannot hurt you at all; the behaviour is pure bluff. The females do have a sting, which they use to paralyse cicadas, but they are focused on hunting and digging, not on defence, and they will not sting unless they are stepped on with bare feet or squeezed in a hand. Stings to humans are rare and, by wasp standards, mild. There is no nest of hundreds of workers to set off, because each female works alone.
Why are there so many big wasps flying low over my lawn in summer?
You almost certainly have a cicada killer nesting aggregation. The wasps favour sunny spots with sparse grass and loose, well-drained soil, such as the edge of a driveway, a slope, a flower bed, or a poorly grassed lawn, and many females may dig their separate burrows in the same good patch of ground. The low, patrolling, hovering flight is mostly males holding territories and watching for females. It looks and sounds threatening, especially with insects this size, but the aggregation is not a colony and poses almost no risk. Growing thicker turf or mulching bare soil usually persuades them to nest elsewhere the following year.
Do cicada killers actually kill cicadas, or just carry them?
The sting paralyses the cicada rather than killing it outright, which is the point. A dead cicada would rot before the wasp larva could eat it, but a paralysed one stays alive and fresh, unable to move or resist, for the week or two the larva needs to consume it. The female stings the cicada on a tree or in flight, then has to transport an insect that often outweighs her back to the burrow, sometimes climbing a tree to launch and glide with it because it is too heavy to lift from the ground. Each larva is given one to three cicadas depending on whether it will become a small male or a large female.
How is a cicada killer different from the Asian giant hornet people worry about?
They are very different insects that get confused because both are large. The eastern cicada killer is a native, solitary, ground-nesting wasp that hunts cicadas, has no colony, and is essentially harmless to people. The Asian giant hornet, sometimes sensationally called the murder hornet, is a social hornet from Asia that builds colonies, attacks honeybee hives, and can deliver a serious sting; a small number were found in the Pacific Northwest around 2019 and 2020 and then eradicated. A big wasp seen over a sunny lawn in the eastern United States in July, carrying or hunting cicadas, is a cicada killer, not a giant hornet.