Field plate · Vespula spp.
Yellowjacket
Glossy yellow-and-black wasps that nest in walls and lawns and turn defensive by August. The late-summer picnic pest is the same insect.
Plate 12 of 28. Drawn in profile to the identification marks named below; the scale rule is a drawing convention — sizes are given in the text.
Identification marks
Workers 10–13 mm, smooth and glossy with bold yellow and black bands, a pinched waist, and no visible hair. In flight the legs dangle less than a paper wasp's. Queens are noticeably larger in spring.
Look-alikes it is confused with
Paper wasps (longer, browner, dangling legs, umbrella nests), honey bees (hairy, amber, and a protected call to a beekeeper, not an exterminator), and bald-faced hornets — which are, in fact, a large yellowjacket.
Where it hides in a house
Abandoned rodent burrows, lawn voids, retaining walls, and — the costly case — wall and soffit voids entered through a single small hole, with a steady two-way stream of traffic on warm days.
Health & property risk, stated plainly
Stings, repeatedly: a disturbed ground or wall nest can produce many stings, and yellowjackets sting without losing the stinger. For people with venom allergy this is an emergency risk, and nests in walls can chew through drywall and fill rooms with wasps if sprayed badly.
What actually works
Never seal an active entrance. Dust treatment into the nest entry by a pro, after dark in cool weather for ground nests, and removal of the nest material from wall voids so it does not feed other pests. Keep sweet drinks covered in August and September.
What doesn't
Spraying a can into a wall void and sealing the hole — the classic route to wasps emerging through a bedroom ceiling, and a fire risk if flammable propellants meet wiring. Boiling water, petrol, and fire on ground nests are dangerous and do not work.
When to call a licensed pro
Yes for wall voids, ground nests near doors and play areas, any nest you cannot see whole, and always where a household member has a sting allergy.