Pipe Organ Wasp Nest

Most people have seen mud nests of the Pipe Organ Wasp, AKA Mud Dauber.  Around the home, the nests are most commonly constructed on a vertical wall or beam.  A location favored by female wasps at my house is on the front porch.  The porch provides plenty of wall surface for nest construction and a roof to keep the nests dry.

Nests are constructed by the female wasp, a shiny steel-blue creature with a long thin waist.  She makes hundreds of trips to haul in balls of mud to form into the tube shaped nests.  Once a tube is completed, the female carries in paralyzed spiders and stuffs them into the tube.  Periodically she’ll lay one egg among the spiders and seal that section of the tube shut with additional mud.  Inside each of these sealed chambers, a single wasp larva will feed on spiders until it is time to pupate.  They will overwinter in this fashion and emerge as adults next spring.

The tube is constructed as a long arched structure, similar to the design of a Quonset hut.  The house forms the flat floor and the nest walls are built by adding mud fingers running from the central line of the tube to the house.  Placement of the fingers progresses in an alternating fashion from side to side.  Color differences in the fingers show that the wasp may visit several different mud sources during the period of nest construction.

While doing some work to the barn roof, I dislodged several mud nests from the barn rafters.  I checked out the debris later to see if anything of interest could be found in the debris.  Most of the fallen nests were old.  The few fresh nests all contained the lozenge shaped cocoons in which the larvae will eventually pupate.  I set undamaged cocoons in a safe place where they have a chance of surviving the winter and hatching new wasps next spring.

This cocoon was damaged in the fall.  Inside was a wasp larva.  The larvae eat just about every bit of the spiders in their cells.  Debris left in the cell is just a bit of dust.

Some cocoons were very light weight, so I cracked them open to see what was inside.  Most were filled with debris with no signs of the larva.

Several were full of the shed skins of Carpet Beetle larvae.  Judging by the number of skins in each cocoon, the beetles must have flourished here.

There are always a few old mud nests on the porch, usually in the corners.  I’ll remove them when they reach the stage where they begin to crumble on their own, but it usually takes them a couple of years to reach that stage.  I think they’re kind of neat to look at.  They remind me of the Mesa Verde Cliff Dwellings.  They’re just smaller and easier to access.