Yellowjacket Season: When Wasp Colonies Peak in Your State

Late summer into autumn, and it is a colony cycle rather than a weather event. A single overwintered queen founds a nest in spring, the colony grows all summer, and it reaches maximum size in the weeks before the first hard freeze. In the northern tier that peak is August and September; across the middle of the country it is September and October; along the Gulf and in California it runs into November. A hard freeze kills every worker.

Two things happen at once. The colony is at its largest of the year, so there are more wasps than at any other time. And the queen stops laying, which ends the exchange that kept workers busy: they had been hunting insects to feed the larvae, and the larvae had been secreting a sugary liquid back in return. With no larvae there is no work and no sugar, so thousands of workers switch to scavenging anything sweet, which is when they arrive at your drink. They are not angrier. They are unemployed.

No, and telling them apart takes one glance at the nest rather than the wasp. Enclosed paper nest, almost always underground in an old rodent burrow, or hidden in a wall void or compost heap. The only sign is a steady stream of wasps in and out of one small hole. The grey, layered paper football hanging in a tree, shrub, or under an eave, with one entrance near the bottom. An open umbrella of bare hexagonal cells with no paper envelope, hung under an eave, a rail, a mailbox, or a grill lid. Only yellowjackets scavenge at food; the other two ignore picnics entirely.

Usually nothing. A nest in a far corner of the yard dies at the first hard freeze and is never reused, so leaving it costs one season. Treat one only when it is somewhere people cannot avoid: a doorway, a play area, a lawn that has to be mown, or a wall void. If it must go, do it after dark when the foragers are home, from as far away as the label allows, with an exit route planned. Wall voids, nests above head height, and any household with a sting allergy are a professional job.

You went over a ground nest. Most yellowjacket colonies live underground in an abandoned rodent burrow with one coin-sized entrance hole and no visible mound. Mower vibration reads as an attack on the nest, which is why these stings arrive in bursts rather than singly. In late summer, stand and watch the lawn for a minute before starting: a colony at peak runs a steady stream of wasps in and out of one spot.

For most people, painful and then over. Swelling well beyond the sting site, even across a whole forearm, is a large local reaction rather than an allergy and settles in a few days. The serious case is anaphylaxis: trouble breathing, swelling of the throat or tongue, dizziness, spreading hives, or vomiting all mean call emergency services immediately. Stinging insects send far more people to hospital each year than snakes do, and this is why.

Yes. A single colony removes a very large quantity of caterpillars, flies, and other insects over a summer, which is free pest control for any garden, and the adults visit flowers for nectar and do a share of pollination. The behaviour everyone objects to is confined to a few weeks at the end of the colony cycle, and it ends on its own with the first freeze.

No. This is about Vespula wasps, the black and yellow insects that nest in the ground and turn up at barbecues in September. If you are looking for the Showtime series, or for Georgia Tech, you want a different site. The search term is genuinely ambiguous, which is why every heading here says wasp.