Wasps become more defensive in late summer because the colony is raising its last brood, which includes males and next year's queens. Nests are built in the ground, in trees, under eaves and inside wall voids and attics. Give any nest a wide berth, and note where it is before anything else is done.
Key takeaways
- The last brood of the season contains males and next year's queens, which is why workers turn protective in late summer.
- Nests can be built in the ground, in trees, under eaves and inside wall voids and attics.
- A bald-faced hornet nest is oval and can be larger than a basketball.
- In a bald-faced hornet colony, workers and males die off at the end of summer and only young queens overwinter.
- Paper wasps are less aggressive than hornets or yellowjackets.
- An August advisory from Michigan State University Extension noted ground-nesting yellowjackets and bald-faced hornets driving many calls that season.
Why do wasps get so defensive in late summer?
Late in the season the colony is raising its last brood, and that brood contains males and next year's queens. The workers guarding the nest are at their most protective.
The change is tied to the calendar rather than to any one nest. The last brood carries the colony's future, so the workers guarding it respond more strongly to anything that comes close. A nest that was quiet in June can behave very differently in late August, even though nothing about the nest itself has been disturbed. A homeowner who has noticed a change in how wasps behave around the house is noticing the calendar at work.
This is why late-summer calls tend to rise. Michigan State University Extension's August advisory noted ground-nesting yellowjackets and bald-faced hornets driving many calls that season. A nest that did not bother anyone earlier in the summer can become a problem as the season turns, and it is worth treating late-summer sightings with more care than early ones.
Where are wasp and hornet nests usually built?
Nests are built in the ground, in trees, under eaves and inside wall voids and attics. Each of those places keeps the nest out of sight until someone is close to it.
Ground nests are the ones people step on, often along a field margin or a mown edge. Nests in trees are easier to see from a distance, but a nest under an eave sits close to doors, porches and windows, where people pass often. The location tells you how much traffic a nest is likely to meet. Checking the trees that overhang a path or seating area is worth the time, since a nest there is close to where people sit.
Inside wall voids and attics, a nest may be entirely hidden. The first sign is often wasps coming and going from a gap at the eave or a loose piece of siding. Those gaps are the points to note before any work is planned, because the entry point is frequently the clearest clue to where the nest sits.
How big can a bald-faced hornet nest get?
A bald-faced hornet nest is oval and can be larger than a basketball. A nest that size is a reason to keep a wide distance from it.
The shape is the first clue. A bald-faced hornet nest is oval rather than flat or open, and at its largest it can be bigger than a basketball. A nest of that size holds a large colony, and the sensible reading is to keep well back and to mark where it is before going anywhere near it.
The colony does not carry on in its present form. Workers and males die off at the end of summer, and only young queens overwinter. A nest seen in late summer is therefore a snapshot of a colony at its largest, and it is the late-summer behavior that makes it worth caution. The size of a nest also suggests how many workers may respond when it is disturbed, so the distance should be wider for a larger one.
Are hornets and yellowjackets the same as paper wasps?
Paper wasps are less aggressive than hornets or yellowjackets. Knowing which kind you have helps you judge how much distance to keep.
The main sourced difference is in temperament. Paper wasps are less aggressive than hornets or yellowjackets, so the species matters when judging how close is reasonable to work. A paper wasp nest under an eave calls for a different level of care than a ground nest with a busy colony in it.
The ground-nesting yellowjackets and bald-faced hornets in the August advisory were the ones driving many calls. A ground nest is the harder case, because it sits closest to foot traffic and can be hard to see until someone is nearly on top of it. Treat every nest with distance, and let the species guide how close you are willing to go. Yellowjackets that nest in the ground can be met in a lawn, which makes a ground nest the more pressing question near a play area.
Why are nests in wall voids and attics harder to deal with?
A nest inside a wall void or attic is out of sight, so the first sign is often wasps entering and leaving through a gap. The nest itself can sit in a space the homeowner cannot easily reach.
Wall voids and attics keep the nest hidden until traffic reveals it. Wasps moving in and out of a gap at an eave or under a soffit are the clue, and the entry point can be the best indication of where the nest is. Watching that traffic for a few minutes, from a safe distance, tells you more than a guess from the outside.
Because the nest is inside the structure, the work is less about the wasps you can see and more about locating the nest. That is why a technician may ask where the traffic is coming from before anything else. An entry point left as it is will keep being used, so noting its position is useful even if the nest cannot be reached right away. Noting the gap's position on the outside of the building, relative to windows and doors, is useful when describing the nest.
Where on a farm do late-summer wasps tend to show up?
Around a farmyard, nests can sit under the eaves of sheds and barns, in outbuildings, in trees near the house and in the ground along field margins. The ground is the place most people walk past.
Farm outbuildings, machinery sheds and barn eaves offer the sheltered overhangs and hidden voids that nests can use. Trees at the edge of a yard and the ground beside a mown margin add to the list. Each of those is a place a person works or walks, which is when a defensive colony becomes a problem. Machinery and stored equipment in an open shed can offer the same sort of hidden spot, and a nest there is easy to overlook until it is close.
Walking a field edge in late summer is a good example. A ground nest that sits quietly in June may be guarded in late August, and the first warning can be a wasp in the grass near the foot. A slow, deliberate walk along the edge, with an eye on the ground, is the habit that keeps that first warning from becoming a sting.
What should I do if I find a nest?
Keep your distance, note the nest's location and type if you can see it safely, and leave the removal to a technician. Describe where it is when you call.
From a distance, note where the nest is: in the ground, in a tree, under an eave or in a wall. Note whether wasps are going in and out of a gap, and how many are moving around it. Mark the spot so that the same place is not walked through by mistake later in the season.
Keep children, animals and yourself away from the area until the nest has been dealt with. Late-summer workers respond to movement near the nest, so a slow, wide detour is the safer habit. Once the location is noted, the next step is the call, and the call is easier to make when the description is already written down. Avoid swatting at wasps or stirring the area, which makes the workers more likely to respond.
When should I call a technician about a nest?
Call when a nest is near a door, a sleeping area, a play area or a path you use often, or when a nest is hidden in a wall or attic. Phones are answered 24/7, and a visit the same day only when a technician is free.
A nest close to where people spend time is a reason to call, because late-summer workers are most defensive near the nest. A nest in a wall void or attic is also worth calling about, since the entry point is what tells a technician where it is. Waiting until the colony is at its largest makes the job harder to plan, so an early call is the better choice.
Describe the location and type of nest, the entry point you have seen and any calls you have already made. The technician will not promise an arrival time, and the visit can be scheduled for when a technician is free. Ask how the nest will be approached before any work starts, so you know what to expect on the day.
Frequently asked questions
Why are wasps suddenly so aggressive in late summer?
The colony is raising its last brood, which includes males and next year's queens. The workers guarding that brood are more protective, so the same nest can behave differently from one month to the next. Late-summer defensiveness is a seasonal pattern rather than a sign of one unusually dangerous nest. Knowing the calendar makes the change easier to plan around.
Where do wasps usually build nests?
Nests are built in the ground, in trees, under eaves, and inside wall voids and attics. Nests in the ground and inside wall voids are hidden, so the first sign is often wasps moving in and out of a gap. Checking the eaves and the entry points of a shed or barn is a simple way to see what is nearby. A quick walk around the outside of the house can show the most likely spots.
How big is a bald-faced hornet nest?
A bald-faced hornet nest is oval and can be larger than a basketball. A nest that large is a reason to keep a wide distance and to mark its location. Only young queens overwinter, so the colony does not carry on in its present form.
Are paper wasps as dangerous as hornets?
Paper wasps are less aggressive than hornets or yellowjackets. That is a statement about temperament, not a guarantee about any single nest. Treat every nest with distance, and let the species guide how close you are willing to work.
Does a ground nest in August need a call?
A ground nest close to foot traffic is a reason to call, especially in late summer. Michigan State University Extension's August advisory noted ground-nesting yellowjackets and bald-faced hornets driving many calls in its season. A nest in a path or lawn that people cross often is the one to report first.
What should I tell the technician?
Describe where the nest is, whether it is in the ground, a tree, under an eave or in a wall or attic, and how much wasp traffic you see. Note which buildings or paths are closest to it. The more exact the location, the easier it is to plan the visit. A photograph of the nest taken from a safe distance is useful if you can take one.
Sources
This guide is general information for Montcalm County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.