What Is That Mud Nest On Your House?

A hard tube of dried mud under an eave, on siding, inside a garage or on the ceiling of a shed is almost always a mud dauber nest. Mud daubers are solitary wasps that hunt spiders. University of Minnesota Extension says they do not defend their nests, so there is little to no risk of stings, and that the nests can be left alone or taken off with a putty knife.

People usually find one in the fall, when the leaves are down and somebody is up a ladder at the gutters. The first instinct is to treat it like a hornet nest and keep well back. That instinct is wrong here, and knowing which nest you are looking at decides whether this is a two minute job or a reason to call about stinging insect control.

Mud Nest Or Hornet Nest?

The building material answers it before you get close enough to see the wasp. Mud daubers carry wet mud in their jaws and plaster it into tubes and cells. Social wasps chew wood fiber into paper, which is why a bald faced hornet nest is gray and papery and a paper wasp comb looks like an upside down umbrella. Clemson Cooperative Extension describes mud daubers as not social insects, although many females may use the same general area for nesting, which is how a garage wall ends up with a dozen nests on it and still has no colony behind any of them.

That last row is the one worth taking seriously in Ohio. Ohio State University Extension's yellowjacket fact sheet notes that the German yellowjacket first appeared in the state in 1975 and is now the dominant species here, and that the right response to one in the air is to walk away rather than swat. We went through the three paper nest builders and where each of them sets up in bee, wasp and hornet nests in Ohio.

What Is Inside It In November?

Not an adult wasp, and not nothing either. Texas A&M's field guide describes the cycle: each female builds and stocks her own nest, lays eggs singly in the mud cells, and the cream colored, legless larvae pupate in cocoons inside those cells and spend the winter there. The Missouri Department of Conservation says the same thing for all of its mud dauber species, which pass the winter as immature insects inside the nests.

So a mud nest in late autumn is a nursery rather than a ruin. The cells tell you which ones are still in use. A neat round hole chewed through the mud is an exit, and that cell is empty. A sealed, unbroken cell still has something in it. The adults that did the building are gone either way: University of Minnesota Extension notes that solitary wasps live only one season and do not reuse nests year after year.

Why The Nest Is On Your House At All

Spiders. A female mud dauber stings spiders into paralysis, packs them into a mud cell, lays a single egg on the pile and seals it up, so the larva has fresh food through its whole development. The University of Michigan's catalogue of sphecid wasps describes the blue mud dauber mass provisioning each cell with spiders, mostly from the cobweb family Theridiidae and the orb weavers of Araneidae, with crab spiders, lynx spiders and jumping spiders turning up less often.

That species has a reputation attached to it. The University of Michigan notes the blue mud dauber is known for preying on black widow spiders, and Texas A&M adds that it takes over the nests of the black and yellow mud dauber rather than building its own, provisioning the stolen cells mostly with widows. Before anyone reads too much into a mud nest on an Ohio garage, the cobweb family those records point to also contains the ordinary common house spider, and we went through which Ohio spiders are actually worth a second look in house spiders in Ohio. The useful signal is simpler: a wall covered in mud nests is a wall where the hunting was good.

Should You Take It Down?

That is a preference, not a safety decision. University of Minnesota Extension puts both options on the table without hedging: when mud dauber nests are found on a home, ignore them or remove them with a putty knife, because the wasps do not defend their nests. Clemson adds that taking nests off by hand may discourage mud daubers from the spot and reduce later generations.

• Scrape rather than spray. The nest is dried mud on a surface, and nothing in the published guidance calls for a pesticide to get it off.
• Work when the adults are not flying. By the time Ohio reaches November, that part is usually settled for you.
• Put something under it. The cells break up into crumbs and whatever was stored inside comes down with them.
• Close the opening behind it if the nest was in a gap. Clemson's advice is that screening or caulking openings that let insects into a building prevents nesting in those spaces.
• Consider leaving the ones nobody touches. Ohio State University Extension's guide to solitary bees and wasps argues against wiping out most of them, since they are pollinators or predators of pest insects, and notes they sting mainly when captured or restrained.

When A Mud Nest Is Not The Real Question

A few situations change the answer. If wasps are moving steadily in and out of one point in the siding, a gap at the soffit or a hole in the ground, there is a social nest in a void and the putty knife is the wrong tool. If the mud keeps reappearing in a dryer vent, an attic louvre or a bathroom exhaust, the opening is the problem rather than the nest. And if the holes are round, drilled into bare deck or trim wood with coarse sawdust underneath, that is a different insect again, which we covered in carpenter bee holes in the fall.

Any of those is worth a look from somebody who does this for a living, which is what wasp and hornet removal is for. The work is the same either way: find what is actually nesting, take the nest out, then close the way back in so the next one has nowhere to start.

If You Would Rather Not Guess

Most mud nests need nothing from us, and we would rather say so than sell a visit. When the nest is somewhere awkward, when there are a lot of them, or when you are not sure the thing going in and out is a mud dauber at all, that is worth a call. State Termite has worked Stark, Summit, Portage, Wayne and Tuscarawas counties since 1933, and the office answers around the clock. Get a free estimate or call 330-494-6199, and if pests come back between treatments, so do we, at no cost.