White faced hornets (Dolichovespula maculata) are large, social wasps native to North America. They are known for building gray paper nests, which are often found hanging in trees, under roof eaves, or inside abandoned rodent burrows. However, white faced hornets sometimes build their nest underground as well. Here’s a quick overview of where white faced hornets nest and why they may choose underground locations at times.
Quick Facts on White Faced Hornet Nests
- White faced hornets build nests made of chewed wood fibers mixed with saliva.
- Nests are enclosed in a paper envelope and contain multiple tiers of hexagonal combs inside.
- A mature nest can be basketball sized and contain thousands of hornets.
- Nests are often found hanging from trees, shrubs, building eaves, or other structures.
- Underground nesting does occur but is less common.
White faced hornets will occasionally nest in the ground, though above-ground locations are more frequently chosen. Factors like soil type, location, time of year, and availability of existing burrows influence whether an underground nest site is selected.
Do White Faced Hornets Prefer Above-Ground Nests?
White faced hornets show a strong tendency to build aerial nests attached to trees, shrubs, and manmade structures. Studies show the vast majority of documented white faced hornet nests are located above ground:
- One study of 46 white faced hornet nests in New York state found 100% were aerial nests attached to branches, walls, or eaves. No underground nests were observed. (Akre, Greene et al. 1980)
- Research in Missouri located 37 white faced hornet nests, all of which were aerial. Most were located in trees. (Landolt, Reed et al. 1999)
- A survey of paper wasp and hornet nests in Illinois found 85% of white faced hornet nests were aerial, while only 15% were subterranean. (Priddy, Williams et al. 2003)
These studies reveal a strong preference for building aerial nests in trees and on structures. However, the Illinois data does show white faced hornets will sometimes nest underground as well.
Reasons for Above-Ground Nest Sites
There are several advantages to aerial nest locations that likely account for white faced hornets’ tendency to choose them:
- Easier to defend – Aerial nests allow hornets to spot predators and intruders from farther away.
- Better ventilation – More air circulation means cooler, drier nest conditions.
- Sun exposure – Sunlight helps regulate nest temperature and kill microbes.
- Protected from floods – Nests are less likely to be damaged by heavy rain or wet ground.
- Access to suspended food sources – Aerial nests allow easier access to tree sap, flower nectar, and other suspended foods.
The vulnerability of subterranean nests to flooding and excess moisture may be a key factor favoring aerial nest placement whenever possible.
When Do White Faced Hornets Nest Underground?
Underground nesting by white faced hornets is considered atypical but can occur under certain conditions, including:
Existing Burrows
White faced hornets may nest underground when suitable abandoned rodent burrows or other cavities already exist. By re-purposing an existing burrow, the hornets save themselves the effort of excavating a nest cavity.
Sandy Soil
If soil conditions make digging relatively easy, such as loose, sandy soil, hornets may excavate their own underground nests more readily. Heavy clay soils are likely avoided.
Hot Weather
During periods of extreme heat, the cooler temperature underground may become more favorable. However, ventilation is still needed to prevent excessive moisture.
Early in Colony Cycle
Queens may be more likely to found nests underground very early in the colony cycle before worker hornets are available to build an aerial nest. However, nests are often relocated above ground later on.
Disturbance
If an existing aerial nest is damaged or destroyed, hornets may temporarily take refuge underground while rebuilding.
While underground nesting does occur in white faced hornets, it appears limited to particular conditions and is much less common than aerial nesting overall. Even hornets with subterranean nests will typically build exposed aerial entrance tubes rather than burying entrances underground as well.
Identifying Underground Nests
Locating white faced hornet nests buried in the ground can be challenging. Some signs suggesting an underground nest is nearby include:
- Seeing hornets entering or exiting a small hole in the ground
- Large numbers of hornets hovering very low to the ground
- Hornets carrying wood fibers or mud into a burrow
- Aggressive guard hornets near a burrow entrance
Disturbed or bare patches of ground, or evidence of excavated soil may also indicate a nest entrance. However, nests are easily overlooked if entrance holes are not directly visible.
Underground nests are most likely to occur in banks, slopes, or at the base of bushes and trees where rodent burrows are often found. Checking for activity at any small burrow entrances can help reveal if a nest is present inside.
How to Confirm an Underground Nest
To verify if an underground cavity contains a white faced hornet nest, experts recommend the following:
- Observe the entrance at various times of day for hornet traffic
- Place small sticks into the entrance overnight and check for removal by morning
- Insert a tube into the entrance and blow or pump smoke in, then check for hornets emerging
- Place a small mirror just inside the entrance to try to spot nest combs deeper inside
Caution should always be taken, as hornets may attack if they detect a threat to the nest. Wear protective clothing when approaching any suspected nest entrance.
For professional removal or destruction of underground hornet nests, pest control experts have specialized tools like fiber optic scopes that allow nests to be verified and monitored from a safer distance.
Dangers of Underground Nests
While aerial white faced hornet nests often pose little danger if left alone, underground nests in close proximity to human activity can create hazards. Some concerns include:
- Greater risk of accidentally disturbing nests when digging, mowing, etc.
- Nearby entrance holes can allow hornets to swarm very close to people
- Difficult to clearly see and avoid nest entrances
- Entrances may be located along children’s play areas
- Livestock can be attacked when grazing near nests
For these reasons, having underground hornet nests identified and eliminated is advisable whenever they are detected near homes, recreation sites, gardens, or areas used by people and pets.
Removing Underground Nests
Removing white faced hornet nests situated underground should always be left to pest management professionals. Serious stings are highly likely if nests are disturbed without proper protective equipment.
To eliminate underground nests, pest pros may:
- Insert pesticide dust into the nest entrance then seal it
- Pump a liquid pesticide into the entrance
- Inject a foaming pesticide to fill all chambers
- Excavate the nest and remove it
Tracking and eliminating all entrances is important, as hornets will dig out new exits if original ones are plugged. Removal is best done at night when all hornets are inside the nest.
For homeowners wishing to avoid using pesticides, removal of aerial nests is recommended over trying to eradicate large, inaccessible underground nests. Preventive measures such as keeping eaves sealed and filling potential nest sites early in the year can also help reduce subterranean nest establishment.
Conclusion
While white faced hornets strongly favor building aerial nests in trees and on structures, they will occasionally nest in underground cavities as well. Though less common than aerial nesting, underground nests do pose increased risks when located close to human activity. Their inconspicuous entrances mean nests often go undetected until disturbance prompts attack. If underground nests are suspected on your property, have a professional inspect and remove the nests to prevent hazards. With prompt removal and preventive exclusion efforts, white faced hornets can be safely managed even when nesting preferences lead them underground.
