Dime-sized holes in the ground, roughly 18 millimeters across, are most often created by solitary ground-nesting bees or wasps. These insects are the leading cause of small, clean, round holes that seem to appear overnight in lawns, gardens, and bare patches of soil. Depending on where you live and the time of year, a few other creatures could also be responsible.
Solitary Ground-Nesting Bees
The most common culprit behind dime-sized holes is a solitary bee. Unlike honeybees, these species don’t live in hives. Each female digs her own individual tunnel in the soil, provisions it with pollen, lays an egg, and moves on. The most widespread groups in North America are mining bees (Andrena) and cellophane bees (Colletes), both active in early spring.
Their tunnels go six or more inches deep and are typically surrounded by a small mound of excavated soil, like a tiny volcano. Females dig during the evening hours, so you may notice new holes appearing by morning. One key giveaway: solitary bees tend to nest in large congregations. If you see dozens or even hundreds of small holes clustered together in a patch of yard, ground-nesting bees are almost certainly the answer.
These bees strongly prefer dry, sandy, well-drained soil with sparse vegetation. Research on one common species found nesting sites had an average sand content of about 77% and significantly more bare ground than surrounding areas. Dense root networks and thick grass obstruct nest digging, so thin or patchy lawn areas, south-facing slopes, and garden edges are prime real estate. If your yard has a bare, sunny spot with sandy or loamy soil, it’s exactly the habitat they seek out.
Solitary bees are not aggressive. They rarely sting, and even when they do, the sting is mild. The nesting activity is temporary, typically lasting just four to six weeks in spring.
Solitary Wasps
Several species of solitary wasps also dig holes in the ground, though their holes tend to be slightly larger than a dime. Cicada killer wasps, the most conspicuous example, create openings about 1.5 inches in diameter with oblique tunnels running 12 to 18 inches long and 6 to 10 inches deep. These are active in mid to late summer, when cicadas are available as prey. A large nesting group can leave behind noticeable mounds of loose soil.
Smaller solitary wasps, like sand wasps and thread-waisted wasps, dig holes closer to dime-sized. Their tunnels are typically found in the same sandy, well-drained soil that ground bees prefer. Like solitary bees, these wasps are not defensive of their nests and pose very little sting risk to people walking nearby.
Wolf Spiders
Burrowing wolf spiders dig holes roughly half an inch across, which is close to dime-sized, in sandy or loose soil. Their burrows have a few distinguishing features. The upper walls are reinforced with layers of silk, and some species build small turrets or raised lips made of debris, sand, and silk around the entrance. Others leave the opening completely flush with the ground.
Wolf spider burrows tend to be solitary rather than clustered. You’ll typically find one hole, not fifty. The spider lives inside the burrow and ambushes prey from the entrance, so you might spot it sitting just inside the hole during warm evenings. These spiders are not dangerous, though they can bite if handled.
Chipmunks, Voles, and Small Rodents
Small mammals sometimes create holes that look similar at first glance, but there are reliable ways to tell them apart. Chipmunk and vole holes are usually 1 to 2 inches in diameter, slightly larger than a dime, and often lack the neat dirt mound that insect holes have. Chipmunks are particularly tidy: they carry excavated soil away from the entrance in their cheek pouches, leaving a clean, inconspicuous opening. Vole holes are often found along runways, which are worn pathways through grass that connect burrow entrances.
Norway rats also dig small ground holes, though these tend to be closer to 2 to 3 inches across and are usually found near foundations, woodpiles, or food sources. If the hole has greasy smudge marks around the rim, a rodent is the likely occupant.
What Earthworm Holes Look Like
Earthworms leave holes, but they’re much smaller than a dime. Nightcrawler burrows measure just 2 to 4 millimeters across, roughly the width of a pencil lead. The telltale sign is a midden: a small pile of dark, smooth, globular cast material about 2 to 5 centimeters wide, often topped with a mat of leaf stems and fragments the worm has dragged into the burrow. If your holes are truly dime-sized, earthworms aren’t the cause.
How to Identify What Made Your Holes
A few quick observations can narrow it down:
- Number of holes: Dozens or hundreds of holes clustered together point to solitary bees or wasps. A single hole, or just two or three, suggests a spider or small mammal.
- Dirt mound shape: A small, symmetrical cone of fine soil around the hole is typical of ground-nesting bees. A large, U-shaped pile of coarser soil suggests a bigger wasp like a cicada killer. No visible dirt mound at all could mean a chipmunk (they clean up after themselves) or a spider.
- Silk at the entrance: Any visible webbing, silk lining, or a raised collar of silk and debris around the rim means a spider made it.
- Edge quality: Insect and spider holes tend to be perfectly round with clean edges. Mammal holes are often slightly irregular or oval-shaped.
- Soil type: Sandy, dry, bare patches of ground strongly favor ground-nesting bees and wasps. Holes in dense, moist clay soil are more likely from rodents.
- Season: Holes appearing in early to mid spring are most likely solitary bees. Holes appearing in July and August are more likely wasps. Holes present year-round suggest a mammal or spider.
Should You Fill the Holes?
If solitary bees are responsible, the best approach is to leave them alone. They’re important pollinators, they won’t damage your lawn long-term, and they’ll be gone within weeks. The holes naturally collapse and fill in once nesting season ends. If you want to discourage them from returning next year, increasing irrigation or thickening your grass cover in that area makes the soil less attractive. Solitary bees avoid damp soils and dense vegetation.
For wolf spider burrows, there’s no practical reason to intervene. The spiders help control pest insects and keep to themselves. If small rodents are the cause, filling holes without addressing the animals just results in new holes. Removing nearby food sources, brush piles, and ground cover is more effective than repeatedly filling entrances.