Yellowjackets, paper wasps, and bald-faced hornets are three distinct insects that homeowners regularly lump together under “wasps.” They look different, nest differently, and vary in how aggressively they defend their colonies. What they share is the ability to sting repeatedly and colonies that grow through summer and peak in late summer and fall.
One important note before getting into these species: honey bees are not wasps. If you have a cluster or colony of bees, contact a local beekeeper before calling a pest company. Honey bee populations are under significant ecological pressure and can often be relocated alive at no cost to you. Exterminating a honey bee colony when relocation is an option is the wrong call.
Identification
Yellowjackets are the ones most people mean when they say wasps. They are stocky, about a half inch long, with crisp yellow and black banded abdomens and a short, narrow waist. They fly quickly and directly, without the dangling legs paper wasps show in flight. In late summer they investigate food at outdoor gatherings, which paper wasps typically do not.
Paper wasps are longer and more slender, three-quarters of an inch to one inch, with a distinct pinched waist. Many species are orange-brown with yellow markings. In flight, the hind legs hang visibly below the body. The open, umbrella-shaped comb hanging from eaves is the clearest indicator. Paper wasps are less aggressive than yellowjackets but will sting if the nest is disturbed.
Bald-faced hornets are technically a yellowjacket species, not a true hornet. They are larger, about three-quarters of an inch, with a black body and distinctive ivory-white markings on the face and abdomen. The nest is a large, gray, papery ball, often football-shaped, built in trees or on building eaves. They defend aggressively with little provocation when you are near the nest.
The European hornet (Vespa crabro) is also present in this region. It is larger still, up to one and a quarter inches, brownish-orange rather than pure black and yellow, and nests inside hollow trees and wall voids.
Behavior and Habitat
All three species are social wasps that build annual colonies. A fertilized queen overwinters, emerges in spring, and begins a small nest alone. Workers, all female offspring, take over as the colony grows. By late summer a yellowjacket colony may contain several thousand workers. Bald-faced hornet colonies are similar in scale. Paper wasp colonies are smaller, typically a few dozen to a few hundred individuals.
In fall, new queens and males are produced. The original colony dies off as temperatures drop. The nest is not reused the following year.
Yellowjackets nest primarily in the ground, in abandoned rodent burrows, or in enclosed voids like wall interiors and attic spaces. Ground nests can be hard to spot until you are close to the entrance, which is when stings typically happen. Wall void nests can grow large enough to push through drywall by fall.
Paper wasps nest in open, exposed locations: eaves, porch ceilings, door frames, and window frames. They are more visible and easier to catch early. Bald-faced hornet nests are usually visible once the colony has grown, though they can be obscured by foliage early in the season.
Signs of an Infestation
For ground-nesting yellowjackets, the first sign is worker traffic: wasps going in and out of a hole in the ground or a crack in a foundation. Do not investigate closely. The nest below may be much larger than the entrance suggests.
For paper wasps, visible nests under eaves and on door frames are the main indicator. Check the undersides of decks, fence rails, and outdoor furniture.
For bald-faced hornets, the nest is visible once the colony has grown. In early spring it may be the size of a golf ball. By midsummer it can exceed a basketball in size.
Inside a wall, look for workers entering and exiting through a small gap in siding or a soffit vent. A faint buzzing or chewing sound from inside a wall during peak season is another indicator.
Health and Property Risks
Unlike honey bees, social wasps retain their stingers and can sting repeatedly. A disturbed colony can mobilize many workers at once. For most people, a sting causes sharp pain, local swelling, and redness that subsides over several hours. Multiple stings can cause systemic symptoms even without a venom allergy, simply from the volume of venom.
For people with venom allergy, a single sting can trigger anaphylaxis, which requires immediate epinephrine and emergency care. Anyone with a history of systemic reactions to stings should carry prescribed epinephrine and should not approach a nest.
Ground-nesting yellowjackets cause most serious stinging incidents. A lawn mower or foot traffic near a concealed ground nest can trigger a mass defensive response. Late summer and fall are the most dangerous period, when colonies are largest and workers are most aggressive.
Treatment Options
Paper wasp nests are the most manageable for a homeowner. A small nest found early in spring can be knocked down at night when workers are inactive. Apply a fast-acting aerosol wasp spray directly at the nest, wait, then remove and bag the nest. Repeat if a new queen restarts at the same location.
Yellowjacket ground nests are dangerous for a homeowner to treat. Professional treatment is the better call. If you treat yourself, do it at night using a dust formulation applied into the entrance. Do not use a liquid spray that can flush workers outward. Wear protective clothing, work fast, and have an exit route. Do not treat during the day or dig up the nest.
Bald-faced hornet nests should generally not be treated by a homeowner. The colony is large and the wasps are aggressive, with little warning before mass stinging. A professional with pressurized insecticide and protective equipment is the right approach.
Wall void nests require a professional. Dust or liquid insecticide is applied through the entry point into the void. The entry is sealed after the colony dies. Wall opening is occasionally needed to remove nest material and prevent stored-product beetle problems in the debris.
A professional treatment uses fast-knockdown insecticide followed by a residual application. For aerial nests, physical removal is standard after treatment. Ground nest material is usually not excavated unless there is a specific reason.
Prevention
There is no way to fully prevent social wasps from establishing near a structure. The best approach is early detection and removal before a colony grows large.
Walk the perimeter in May and June and look under eaves, porch ceilings, and deck undersides for new nests. A paper wasp nest at golf-ball size is a quick job. The same nest in August is a different problem.
Seal gaps in siding, soffit, and around utility penetrations that yellowjackets could use to enter a wall void. Check soffits and attic vents with damaged screening.
Keep outdoor garbage in sealed containers. Yellowjackets are attracted to protein and sweet food and will persist near accessible food waste.
If you have had a ground nest in a particular spot before, monitor that area early in the season. Queens establishing new colonies often return to the same type of location.
What It Costs
Paper wasp nest removal typically runs $75 to $150 for a single accessible exterior nest. Yellowjacket ground nest treatment runs $150 to $300. Bald-faced hornet removal runs $200 to $400. Wall void treatments range from $200 to $500 depending on nest size and whether wall access is needed. Most companies charge a flat fee per nest and some offer a short warranty period.
When to Call a Professional
Call a professional for any yellowjacket ground nest near a structure or in a lawn with regular foot traffic. Do the same for any bald-faced hornet nest accessible to people or larger than a softball. Wall void nests are always a professional job.
For paper wasps, use your judgment based on nest size and location. A small nest under an eave away from foot traffic is manageable at night. A nest over a frequently used door or near where children play is worth a call.
Do not wait until fall. By September, a colony that should have been treated in July is many times larger and proportionally more dangerous.
See also: Cicada Killer Wasp, Mosquito, Asian Lady Beetle.