The appearance of a hole in the soil often prompts concern, but many insects, including bees, wasps, and ants, use the ground for shelter, reproduction, and food storage. Identifying the insect responsible requires recognizing its size, behavior, and the characteristics of the entrance hole. Understanding which insect is digging helps determine if the hole is a nuisance or a natural, beneficial part of the local environment.
The Large Hole Makers Solitary Wasps
The most conspicuous holes in lawns and gardens are often made by large, solitary wasps, such as the Cicada Killer wasp (Sphecius speciosus) and various Sand Wasps. Female Cicada Killers, measuring up to 1.5 inches long, excavate substantial tunnels in loose, well-drained soil. These openings are typically about 1.5 inches in diameter and are used to store paralyzed cicadas as food for their developing larvae.
Excavation results in a distinct, U-shaped or crescent-shaped mound of soil piled around the entrance. Despite their intimidating size, Cicada Killers are not aggressive toward people or pets because they are solitary hunters and do not defend a social nest. Females reserve their powerful sting exclusively for their cicada prey.
Sand Wasps (family Crabronidae) are slightly smaller, usually measuring three-quarters of an inch to one inch long, and prefer sandy or bare, exposed areas. They create short, individual tunnels for their eggs, provisioning them with paralyzed flies. Although each female digs her own nest, hundreds of Sand Wasps may nest in close proximity, which can give the false impression of a communal colony.
This aggregation of nests, often found on sandy playgrounds or sunny patches of lawn, indicates suitable habitat, not a unified defense. Like the Cicada Killers, Sand Wasps are non-aggressive and will only sting if they are directly handled or accidentally stepped on. Their presence is beneficial as they are effective natural predators of pest flies.
Small and Numerous Ground Bees and Ants
Numerous, smaller holes are commonly made by ground-nesting solitary bees and various ant species. Solitary ground bees, often called mining bees (Andrena or Colletes species), account for nearly 70% of all bee species. They build individual, unbranched tunnels in the soil, typically measuring less than half an inch in diameter, and are usually found in areas of sparse vegetation or thin grass.
The entrance to a ground bee burrow is frequently marked by a small, volcano-shaped pile of fine, circular soil particles, known as a tumulus. These bees do not form colonies and are exceptionally docile, rarely stinging unless they are physically trapped against the skin. They are active for only a few weeks in the spring or early summer, making them important, but temporary, pollinators.
Ants also create ground holes, but their activity results in structures built to house a large, social colony. The most recognizable ant nesting site is a mound of finely textured soil or sand, which can be small and simple or large and complex with a central entrance hole. This material is displaced soil from the extensive network of subterranean galleries and chambers that form the colony.
The size of the entrance hole is small, usually only a fraction of an inch, corresponding to the size of the worker ants. Unlike the single-purpose burrows of solitary bees and wasps, ant nests often extend deep underground to maintain stable temperature and humidity for the queen and brood.
Reading the Signs Hole Characteristics and Location
Identifying the insect responsible for a hole relies on careful observation of the physical trace left behind. The diameter of the opening is a primary clue, with holes exceeding one inch generally pointing toward the largest digger wasps. Openings that are less than half an inch, but are numerous and concentrated in one area, often indicate the presence of ground-nesting bees.
The shape of the soil mound around the entrance can also provide a clear distinction between the major groups of excavators. A crescent or U-shaped pile of coarse dirt is characteristic of a large digger wasp, as the female pushes the soil out behind her as she backs out of the tunnel. Conversely, a volcano-shaped or circular mound of finely pulverized soil often belongs to a ground bee, or a simple, irregular pile of fine grains points to ant activity.
Location and soil type are also significant diagnostic factors in determining the inhabitant. Insects that prefer loose, sandy, or bare soil in sunny, well-drained areas are typically solitary wasps or bees, who require easy digging and warm temperatures for larval development. Holes found in high-traffic areas, near paved surfaces, or in fine-grained, structured mounds are more likely to be the work of social insects like ants.
When to Intervene Management and Coexistence
The appropriate response to ground holes often involves a strategy of coexistence, since most solitary insects are beneficial pollinators and pest controllers. Solitary ground bees and wasps are non-aggressive and their presence is temporary, lasting only a few weeks of the year. Tolerating their temporary nesting activity is the most environmentally sound approach.
Intervention becomes a consideration when the insects pose a safety risk or cause structural damage to lawns and patios. For instance, the aggressive, social Yellow Jacket wasp, which sometimes nests in abandoned rodent burrows, is a genuine threat that may require professional removal. Similarly, ant colonies that undermine walkways, patios, or home foundations may warrant management due to the risk of structural instability.
Before resorting to chemical treatments, non-toxic cultural practices should be employed. Maintaining a dense, healthy turf with regular watering can discourage many ground nesters, as they prefer dry, bare, or sparsely vegetated soil for digging. Filling in bare patches of soil with mulch or plants can also eliminate suitable nesting sites.
If non-toxic methods are insufficient and the insect is confirmed to be a social pest, physical exclusion or targeted, non-residual organic treatments are better options. Diatomaceous earth, a fine powder that dehydrates insects, can be dusted around the entrance hole of a nuisance nest, but it must be applied carefully to avoid affecting beneficial species. For persistent or high-risk infestations of social wasps, consulting a professional who practices integrated pest management is the safest course of action.