Several types of wasps build their nests underground, but the two you’re most likely to encounter in your yard are yellowjackets and cicada killers. These ground-nesting wasps look and behave very differently from each other, and knowing which one you’re dealing with determines whether you need to worry. Yellowjackets are aggressive social insects that build large colonies underground, while cicada killers are solitary giants that rarely sting people despite their intimidating size.
Yellowjackets: The Most Common Ground Nesters
Yellowjackets are the ground-nesting wasps most people run into, often literally. They’re half an inch to one inch long with jagged bright yellow and black stripes and a very narrow “waist” that’s barely visible. They typically move into abandoned rodent burrows, and if the hole isn’t big enough, they’ll moisten the surrounding soil and dig it out to expand the space.
Inside that burrow, yellowjackets construct a surprisingly complex nest out of paper, made from wood fibers mixed with saliva. The nest has multiple tiers of vertical cells enclosed by a paper envelope with a single entrance hole. A colony starts each spring with one queen and can grow to between 1,500 and 15,000 individuals by late summer, depending on the species. Nine species of ground-nesting yellowjackets live in Pennsylvania alone, and they’re common across most of the United States.
This is the ground wasp you need to respect. Yellowjackets defend their nests vigorously, and that defensive behavior gets worse as summer progresses, colonies grow larger, and food becomes scarcer. August and September are peak conflict months. The most common scenario reported to university insect labs every year: someone runs a lawnmower over a ground nest and gets swarmed. Unlike honeybees, yellowjackets can sting repeatedly. They’ll also sting away from the nest if you swat at them while they’re scavenging food at a picnic or crawling into soda cans.
Cicada Killers: Big but Mostly Harmless
Cicada killers are the wasps that make people panic based on size alone. Females range from 1.5 to nearly 2 inches long, making them one of the largest wasps in North America. Males are slightly smaller, topping out at about 1.5 inches. Despite their size, these wasps pose very little threat to people.
Males are the ones you’ll see hovering aggressively near burrow sites, but they don’t have a real stinger. What looks like a stinger is actually a non-functional pseudostinger. Females do have a working stinger, but they use it to paralyze cicadas, not to defend territory. You’d essentially have to grab one or step on it barefoot to get stung.
Female cicada killers dig burrows in dry, sandy, loose soil. These tunnels can reach 12 to 15 inches deep and extend up to 36 inches long. They have specialized spurs on their back legs built for digging, and the excavation produces noticeable piles of soil on your lawn. Inside each tunnel, the female constructs multiple cells (similar to a mason bee). She hunts annual cicadas in July and August, catches them mid-flight, stings them into paralysis, and drags or glides them back to the nest. She deposits a cicada into each cell, lays an egg on it, and the larva feeds on the cicada over about two weeks before pupating for the winter.
Adults start emerging in late June and July. Males come out first and wait for females. After mating, females spend several weeks feeding, digging, and hunting before the cycle ends. The larvae overwinter in their cocoons underground and pupate the following spring.
Other Ground-Nesting Wasps
Beyond yellowjackets and cicada killers, you may encounter other solitary wasps that nest in the ground. Scoliid wasps, sand wasps, and various digger wasps all create individual burrows in soil. Like cicada killers, these solitary species are generally docile. They don’t have large colonies to defend, so they have little reason to sting you. If you see individual wasps entering and exiting separate small holes in bare or sandy patches of your lawn, you’re almost certainly looking at solitary ground nesters rather than a yellowjacket colony.
The key distinction is social versus solitary. A yellowjacket colony has hundreds or thousands of workers using a single entrance hole, and they’ll defend it collectively. A solitary wasp has one female per burrow, no worker caste, and minimal interest in you.
Why Ground Wasps Are Worth Keeping Around
Ground-nesting wasps play a significant role in controlling pest populations. Adult female wasps of many species hunt insects and spiders to feed their developing larvae, and without them, leaf-eating and seed-eating insect populations would go largely unchecked. Yellowjacket colonies consume enormous quantities of caterpillars, flies, and other garden pests throughout the summer.
Once wasps reach adulthood, their diet shifts from protein to carbohydrates, and they become incidental pollinators as they visit flowers for nectar. Their bodies are smoother than bees, so they carry less pollen, but they still transfer enough to matter. Wasps account for roughly 15% of total flower-visiting insects. They tend to visit shallow flowers where their relatively short tongues can reach the nectar.
When Ground Wasps Are Active
Ground wasp activity follows a predictable seasonal pattern in temperate climates. Yellowjacket queens emerge in spring and start colonies from scratch. These colonies build steadily through the summer and hit their maximum size in August and September, which is when encounters spike. The entire colony dies off after the first few hard frosts in fall. Only a small group of newly mated queens survives the winter, tucked into sheltered spots like rotting logs, to start the cycle again the following spring.
This natural die-off is important to know about. If you find a yellowjacket nest in a low-traffic corner of your yard in September, simply waiting a few weeks for freezing temperatures will eliminate the colony without any intervention. That nest will not be reused the following year.
Cicada killers follow a tighter schedule. Adults are active from late June through August, coinciding with the emergence of annual cicadas. By early fall, the adults are gone and the larvae are sealed underground for the winter.
How to Handle a Ground Nest Safely
For solitary wasps like cicada killers, the honest answer is that you probably don’t need to do anything. The burrows are temporary, the wasps are not aggressive, and they’re actively reducing your local cicada population. The main nuisance is the soil piles on your lawn, which are cosmetic.
Yellowjacket nests are a different story, especially near high-traffic areas. If you decide to treat a ground nest yourself, the single most important rule is timing. Treat at night, when nearly all the wasps are inside the nest and far less active. During the day, locate the entrance hole and note exactly where it is so you can find it in the dark.
A single application of insecticidal dust directed into the nest opening is the most effective DIY approach for ground nests. The wasps track the dust into the nest on their bodies, contaminating the entire colony. Most nests die off within one to two days. You can apply the dust using a bulb duster or even a dry, empty liquid detergent bottle filled with a few inches of dust (add a couple of pebbles to prevent caking, and shake before use). Quickly dispense several puffs into the opening, then move away fast.
After treatment, leave the nest entrance open. Don’t block it with soil or a rock. You want the remaining wasps to move freely through the treated opening so they pick up more dust. If you shine a flashlight, aim the beam to the side of the entrance rather than directly into it, since light can startle the wasps and send them flying toward you. Wearing protective clothing sealed at the wrists, ankles, and collar is strongly recommended.
For large nests, nests inside wall voids, or any situation where you’re not confident in the approach, calling a professional pest control company is the safer choice. A botched treatment on a yellowjacket colony with thousands of workers is one of the more dangerous pest control situations a homeowner can face.
Keeping Wasps From Nesting in Your Yard
Yellowjackets favor sheltered, undisturbed ground with existing holes, particularly old rodent burrows. Filling in rodent holes as you find them removes potential nesting sites. Keeping your lawn thick and well-maintained reduces the bare or thin patches where both yellowjackets and solitary wasps prefer to dig. Regular foot traffic and mowing in an area also make it less attractive as a nest site, since wasps prefer spots that aren’t frequently disturbed.
Cicada killers specifically seek out dry, sandy, loose soil in sunny areas. Increasing soil moisture through regular watering and improving ground cover with dense grass or mulch makes those areas less suitable for burrowing. If cicada killers return to the same patch of your yard year after year, changing the soil conditions in that spot is the most reliable long-term fix.