Which wasps you will actually run into in Montana
Start with where the nest is, because location narrows the species faster than color does. A hole in the ground with steady two-way traffic is almost always a western yellowjacket, the wasp UC integrated pest management researchers name as the dominant scavenger of the western states. A gray envelope the size of a football, closed except for one hole near the bottom, is a bald-faced hornet. Penn State reports the species across most of the contiguous states, and Montana sits well inside that range. They are large, striking, black and white, and they defend the envelope hard, but they do not scavenge at your plate. An open comb with visible cells, hanging from a short stalk under a porch ceiling or a shed rafter, means paper wasps. Native Polistes species build these in the open. The introduced European paper wasp builds the same comb but hides it inside cavities: hollow rail ends, post caps, gas grill frames, downspouts. That habit is why people in Bozeman and Missoula keep finding nests in objects rather than on buildings, and why capping cavities matters more than spraying eaves.
Month by month, from spring queen to hard freeze
April and May belong to single queens. Each one that survived the Montana winter finds a spot, builds a comb of a few dozen cells, and raises the first batch of workers alone. There is no colony to defend yet, and a nest found now comes off with a garden hose. June and July are the build. The first workers take over foraging and construction, the queen does nothing but lay eggs, and the nest doubles and doubles again. Most people do not notice anything at this stage because the wasps are hunting caterpillars and flies, not visiting the deck. August, September, and October are the problem months. Worker numbers peak, the colony starts raising next year's queens and males, and the sugary secretions the larvae fed to adults dry up. That is the switch that turns yellowjackets into scavengers at trash barrels and grills. With summer highs near 85 degrees, activity in this window runs from mid-morning through evening. The first hard freezes end it. Workers die, the queens scatter to overwinter, and the empty nest stays where it is.
What a first visit should look like
Expect the first several minutes to be watching, not spraying. A technician stands back and follows the flight lines to find the real entrance, which on a ground nest can be several feet from where somebody got stung, and on a wall nest is frequently not the gap you assumed. Most of the actual work happens at dusk or after dark. That is not for atmosphere. Foragers are back inside then, the colony is less responsive, and a dust or aerosol placed at the entrance gets carried through the whole nest by wasps walking over it. Daytime treatment of a big August colony mostly kills the ones that happen to be home. The visit should end with a plain explanation of what happens next: how long traffic will continue, when the entrance can be sealed, whether the nest itself will be removed, and what to do if wasps are still flying in three days. On an acreage, ask the applicator to walk the shed and barn eaves while there, since a place with outbuildings rarely has just one nest.
Why one nest costs more than another
Three things move the number more than anything else: where the nest is, how high it is, and how far the truck has to drive. A paper wasp comb on a front porch at six feet is a short stop. A yellowjacket colony in a second-story soffit needs a ladder, a longer application wand, and someone comfortable working at height. Ground nests sit in the middle. The treatment is straightforward but the entrance has to be found in daylight and worked in the dark, and lawns often hide more than one opening. Wall void jobs cost the most predictably, because they usually take a treatment visit plus a return trip to confirm the colony is dead and close the gap. Distance is a genuine Montana factor. Places outside Billings, Great Falls, or Kalispell carry drive time that a subdivision call does not, and some companies price a rural trip charge separately. Ask about that directly. Ask too whether removal of the nest and sealing of the entry are in the quoted figure or billed as extras, since that single question explains most of the gap between two bids on the same nest.
Nests around outbuildings, shops, and equipment
Sheds, shops, and barns are where Montana wasp problems hide until fall. These buildings are open at the eaves, quiet for weeks at a time, and full of the sheltered rafter corners a spring queen is looking for. Nobody is inside to notice the comb in June, so the first contact is often somebody reaching for a tool in September and putting a hand next to a full-sized colony. Stored equipment is its own category. European paper wasps in particular treat any enclosed tube as a nest cavity: trailer frames, mower decks, gas grill bodies, irrigation pipe stacked against a wall. Starting a machine that has a comb inside it is a genuinely dangerous surprise. The fix is a routine rather than a treatment. Walk the outbuildings once in late May and again in early July with a flashlight, look at every rafter bay and the underside of every shelf, and knock down anything small. Cap or plug open pipe ends. If you find something the size of a grapefruit or larger in an active shop, stop and get an applicator instead of trying to knock it down between chores.
When a wasp nest counts as an emergency
Most nests are a scheduling question. A handful are not, and the difference is about who is exposed rather than how big the colony looks. It is urgent if anyone on the property has reacted badly to a sting before. Allergists at the American College of Allergy, Asthma and Immunology report that a prior systemic reaction carries roughly a 60 percent chance of a similar or worse response next time, and they put potentially life-threatening venom reactions at 0.4 to 0.8 percent of children and 3 percent of adults. Adults are the larger risk group, so a household with no kids is not automatically in the clear. It is urgent if the nest sits at a door, on a stair rail, at the mailbox, or anywhere someone brushes past without looking. It is urgent if wasps are appearing inside the house, because that means the colony has found a path through the wall. Everything else can wait for an appointment. A hornet envelope in a tree at the back of a Montana lot, with nobody underneath it, will be empty after the first hard freeze and never used again.