Wasp Nest Question

My son just found a giant gray, papery nest (I think it’s a nest) on the ground in our backyard. I told him not to touch it. Is that a wasp’s nest and are there still wasps in it?—A. C., Georgetown, MA

Answer

It does sound like it could be a wasp’s nest, probably the nest of baldfaced hornets. If the nest is laying on top of the ground, it probably fell out of a tree. You might even see the twig where it was attached built into the nest. Or, an animal, like a raccoon, could have knocked it out of the tree in order to feed on the wasp larvae inside.

Baldfaced hornets are wasps that are black and white in color. Although they are technically yellowjackets, they are less aggressive than our yellow and black yellowjackets. They attach their papery nests to branches in trees or bushes, or under roof overhangs, or less often in attics or sheds.

Wasp Nests Are Not Re-used From Year to Year 

A baldfaced hornet’s nest is made up of chewed wood and saliva and looks like thin layers of gray and brown paper (see What Makes Those Big, Paper Nests in Trees?). The nest is shaped somewhat like a bloated pear with the opening hole at the narrower, bottom end. The nest fully covers layers of combs that contain larval cells. A fully mature baldfaced hornet’s nest can be bigger than a basketball.

As to whether or not the nest is still active, that would be hard to say without observing it. That depends on whether you see wasps entering or leaving the nest, and also on the size of the nest. Baldfaced hornets (and other yellowjackets) don’t re-use their nests. If it was left from last summer, it should be quite large. If it’s a current nest, it will still be in the growing stage since the colony (and the nest) won’t be fully grown until late summer.

Even if it’s an active nest that fell out of a tree, the wasps will probably abandon it shortly. But be forewarned that any larvae in the nest could continue to develop and wasps may emerge later. I’ve known more than one person who hung a large, abandoned wasp nest indoors for display only to have wasps emerge days later!

Photo: Joangray, mehamaOR (Own work) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons