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Bald-faced hornet nests: paper globes in the trees, seen from afar

July to October

That gray, teardrop-shaped paper globe hanging in a tree has been growing all summer and now holds 100 to 400 hornets; it is a marvel of chewed-wood architecture, and the viewing distance is generous.

Why this time of year

Nests often go unnoticed until mid-to-late summer, when they peak at basketball size or larger, so August and September are when families suddenly discover one that has been overhead all along.

How to notice it

  1. Scan high branches, eaves, and big shrubs for a gray papery globe with a single entrance hole at the bottom.
  2. From well back, watch the traffic: workers streaming in and out of the bottom door.
  3. The paper is chewed wood fiber; binoculars show the swirled bands of different trees they harvested.
  4. The whole colony dies with the cold except next year's queens, and the nest is never used twice, so a winter nest is a safe museum piece once truly abandoned.

Try this with kids: From a safe distance, can you spot the front door at the bottom of the nest?

a bald-faced hornet is a large black-and-white wasp; the nest paper is wood they chewed to pulp

Safety

  • They defend the nest and will usually attack within about 3 feet of it, and each hornet can sting repeatedly; watch from well back and never shake the branch.
  • They can turn especially aggressive around the first frosts, so fall is for distance, not dares.
  • If a nest hangs somewhere avoidable, the extension advice is simply to mark it and stay away; anyone with sting allergies should give it the widest berth.

Sources

  • yardandgarden.extension.iastate.eduThe nest is composed of tiers of combs within a thick multilayered outer shell of paper-like chewed wood fiber, with a single opening at the bottom, usually attached to a tree branch; the peak worker population is 100 to 400 hornets by the end of summer; each nest is built from scratch each year and the previous year's nest cannot be reused; queens are the only colony members able to survive the winter; hornets will usually attack if someone approaches within 3 feet of the nest.
  • yardandgarden.extension.iastate.eduNests can be remarkably large, sometimes the size of a basketball or larger; by mid-to-late summer nests peak in size and can include several hundred adult hornets; if a nest is found, do not try to get close or touch it; elevated nests can usually be safely ignored.
  • apps.extension.umn.eduActive from spring through fall, although the presence of nests may not be detected until mid to late summer; occupants of nests do not survive freezing temperatures and nests are not reused.
  • extension.unh.eduBald-faced hornets prefer eaves, horizontal branches, or similar rain-protected sites; the colony gets larger as the season progresses, and once the first frosts come the wasps may become especially aggressive, with colony size at its largest; mated females disperse to individual overwintering spots and none survive the winter in the nest; if a colony is somewhere you can simply avoid, mark the spot and stay away; large teardrop-shaped nests are made by bald-faced hornets.

In the guide for July, August, September, October

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