Ground Hornets

Facts about Ground Hornets & Getting Rid of Them

General Information

Particularly widespread in Southern New England and other areas east of the Continental Divide, the ground hornet is a predatory insect scientifically named Sphecius speciosus. The common name of ground hornets is a bit of a misnomer, as the insects are actually a species of digger wasp belonging to the family Crabronidae. Also known as cicada killers, ground hornets rank among the largest digger wasps found in the United States. Unlike social varieties of stinging insects that form large colonies in nests or hives, the ground hornet is categorized as a solitary wasp and digs burrows individually. The insects naturally control the local cicada population and typically exhibit docile behavior unless threatened. Nevertheless, the ground hornet sometimes becomes a pest when large numbers of the digger wasp construct burrows and nest beside each other in the yards of New England homeowners.

Appearance & Identification

What does a ground hornet look like?
One of the largest wasp species found in the New England region, ground hornets measure up to two inches in length as adults, with females growing slightly larger than males. The ground hornet has a black body featuring yellow markings on the thorax and resembles a yellow jacket in appearance (only larger in size). Three pairs of yellowish legs extend from the sides of the body, while the wings are reddish-orange or brownish. Female ground hornets boast a stinger at the rear of their abdomen.

Habits/Habitat

Classified as both solitary and digger wasps, ground hornets work individually to construct subterranean burrows used as nesting sites. The burrows generally measure up to an inch and a half in diameter, 10 inches in depth, and 18 inches in length beneath the surface of the ground. Typically situated in loose or sandy soil, each burrow features a mound of dirt that surrounds the entrance hole in the shape of a horseshoe. Ground hornets dig burrows in a variety of settings, including forests, grasslands, urban parks, and residential areas. Golf courses, planters and flower beds, and the dirt bordering driveways, sidewalks, and patios serve as popular nesting sites for ground hornets in urbanized areas of New England. Females dig the burrows and lay the eggs, while males guard the nest. Despite lacking the ability to sting, male ground hornets defend the nest vigorously and drive intruders away by buzzing loudly and flying aggressively. While female ground hornets possess stingers, the insects rarely use their stinging capabilities to protect the underground nest.

Diet

What does a ground hornet eat?
The female ground hornet employs her stinger primarily to paralyze cicadas, which the stinging insect carries back to the nest to use as a food source for newly hatched larvae. Ground hornets capture cicadas prior to laying eggs to ensure the availability of food as soon as the larvae hatch. While ground hornet larvae feed on cicadas, adults consume the nectar of flowering plants.

Reproduction

Male ground hornets, while aggressively territorial toward each other, try to attract and mate with passing females during late summer. After mating, females begin digging burrows and catching cicadas in preparation for the laying of eggs. Ground hornets construct a row of cells or chambers at the end of the burrow, place a cicada inside each cell, and lay an egg directly on the paralyzed animal. Larvae hatch from the eggs in about three or four days and feed on the live cicada. Newly hatched ground hornets remain in the nest for at least 10 months, as the newborn larvae overwinter in the underground burrow, complete the pupal stage of the life cycle the following spring, and become sexually mature adults about a year after hatching. At 10 to 12 months of age, ground hornets emerge from the nest to mate and begin the life cycle for a new generation. The lifespan of ground hornets is 13 months, as adults die soon after mating and laying eggs.

Problems Caused by Ground Hornets

Normally docile and unthreatening, ground hornets help control the local cicada population and rarely sting humans. The ground hornet causes problems, however, when large numbers of the insects converge on the same nesting site and dig burrows in close proximity to one another. Ground hornet burrows create unsightly piles of displaced soil and unwelcome holes around yards as well as areas like parks and golf courses, where the attractiveness of the lawn is an important feature. Due to their large size relative to other wasps, ground hornets also incite fear in people frightened of other stinging insects. Male ground hornets in particular prove frightening when the insects fly aggressively at humans trespassing near a nest site.

Signs of Infestation

The presence of burrows serves as the primary sign of a ground hornet infestation. Ground hornets tend to dig burrows in loose or sandy soil and construct entrance holes measuring about an inch and half in diameter. While sometimes constructed under the cover of shrubs or other low-lying vegetation, ground hornet burrows are often conspicuously positioned in sunny areas. Ground hornets leave a telltale, horseshoe-shaped pile of excavated dirt at the opening of each burrow.

Prevention

Because ground hornets prefer to nest in loose soil, New England homeowners should keep lawns properly watered and drained. Planting additional vegetation or placing a layer of mulch over areas of exposed soil may also help deter ground hornets from digging burrows. Residents may want to insert a woven ground cover just beneath the sandy topsoil to prevent ground hornets from burrowing into the ground. If a ground hornet infestation poses a legitimate threat to people or property, homeowners should seek professional assistance from a pest control service in the New England area. Though typically docile and harmless, ground hornets will sting when grabbed or threatened, making the handling of the insects best suited for an experienced pest control professional.