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Mud Daubers

Probably the most familiar of solitary wasps are the mud daubers, which (OK, it's obvious) build their homes with mud. Chances are you've seen the lumpy, dried-mud nests of the black-and-yellow mud dauber (scientifically and appropriately named Sceliphron caementarium ) or the tidier, parallel-tube architecture of the organ pipe wasp ( Trypoxylon politum ). Both species gather mud from the banks of puddles and pools by rolling the clay into pea-size pellets and flying it, one pellet at a time, to a suitable homesite—usually a house or barn wall, a rafter or the eave of a roof. There, spreading mud in overlapping semicircles and buzzing heartily as she works (only females build nests), the wasp plasters together a hollow, tubular cell. As soon as she completes a cell she flies off in search of a spider, paralyzes it with a sting (wasps never use their stingers to kill prey except in self-defense), then grasps it between her jaws and forelegs and flies home. The mud dauber then shoves the stunned insect (or sometimes several of them) into the cell, lays a single egg in the compartment, closes it off and proceeds to build and stock other cells beside or on top of the first. Most dauber nests contain from six to 20 cells, although much larger nests have been recorded.

Once all the cells have been stocked and an egg laid in each, the wasp covers the nest with an outer layer of clay and leaves for good. Soon white, grublike larvae hatch from the eggs and feast on the paralyzed spiders. A few days later, the well-fed larvae spin cocoons in which they pupate, or develop into adult insects. The transformation takes about three weeks, after which each mature wasp chews a small hole in the wall of its cell and flies away to mate. All wasps go through this four-stage process—egg, larva, pupa and adult. As you may remember from biology class (or from Invasion of the Body Snatchers ), this is called complete metamorphosis .

The mud dauber's tendency to build nests on manmade structures and its peculiar habit of buzzing loudly as it works are unfortunate. For those reasons alone, countless nests end up crushed under the butt end of a broomstick or soaked in insecticide. Too bad, because mud daubers are among the meekest of wasps—you virtually have to pick one up and squeeze it to make it sting—and are effective predators of household spiders. One species, in fact—the blue mud dauber ( Chal-byion califomicum )— specializes in capturing black widow spiders. (This dauber is also known as the blue burglar for its habit of breaking into other dauber nests, tossing out all the larvae and spiders.) Other types of daubers prey on cabbage loopers and other garden pests. In short, mud daubers are good wasps to have around.

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