Summer World_ A Season of Bounty - Bernd Heinrich [34]
The next year the organ-pipe mud daubers were gone from our house. The remaining nests on our house had all been pecked open, probably by woodpeckers or chickadees. I checked in a neighbor’s barn, and deep inside, above the horse stable in the ceiling of the haymow, I found numerous mud nests of another species, the blue mud dauber, Chalybion californicum, plastered onto the wooden beams. This species attaches successive cells laterally, next to each other, rather than underneath each other as the organ-pipe dauber does. These nests were also packed with paralyzed spiders, although any one cell contained a variety of species. There were white and yellow crab spiders, brown orb web spiders, and still others. In the western United States this species of mud dauber is renowned for preying on the infamous black widow spider.
Fig. 15. A three-celled nest (detached from a barn beam) of the blue mud dauber, and the spiders out of one of these cells along with the wasp grub found with them.
The summer work of the insects was, as it turned out, not totally benign; one managed to “bug” our heating system. When I went to check out and prepare our outdoor wood-burning furnace, which pipes the heat into our house through a water system, I found it faulty. The water gauge, a vertical tube, stayed empty rather than filling up as it was supposed to when I turned on a valve, so I could not risk making a fire. Luckily I noticed some debris in the bottom of the tube and thought of leaf-cutter bees. These solitary bees make their nests in the galleries in wood excavated by long-horned beetle larvae, or substitutes thereof, and line them with green leaf pieces that they cut from whole leaves. The green leaf then wraps their egg and the pollen for the larva that they add next before sealing the tube nest with mud. I sent some of the remains that I could fish out of the furnace water gauge to Kevin O’Neil, an expert on bees, and he confirmed that a leaf-cutter bee had indeed bugged our furnace.
Fig. 16. The four wasps (not to scale). Center, enlarged: Blue mud dauber carrying a paralyzed spider. Right: Grass-carrying wasp and organ-pipe mud dauber. Left: Nest parasite of the organ-pipe mud dauber.
These four species of “house-barn” wasps, three of which are anatomically similar, plus the bee, have behaviors that are strikingly different. Their behaviors are, like their anatomy, presumably encoded on their DNA but expressed only in response to specific cues. Like most adult insects’ lives, theirs are short—a matter of weeks. Since there is little time for experimenting and learning, such animals must necessarily get everything right almost from the moment that they emerge from their pupa. The newly emerged mud dauber flies off soon after its wings harden, and it finds mud! The dauber “knows” how to pick up and carry mud, where to go with it, and—more amazingly—how to make a nest out of it, of a very specific shape. Of the hundreds of thousands of potential things the wasp could search out, it then looks for specific kinds of prey (or it looks in specific ways so that it finds only those kinds). It responds to very specific, minute details out of thousands that it encounters. Just as we pick out what vegetables to buy at a market, it makes an incredible number of choices every second. Its choices are predetermined by genetic instructions. There is little flexibility. And the next species has entirely different instructions. If I wanted someone to exactly duplicate any wasp’s behavior, I would have to write an encyclopedia of instructions, and even so, he or she would almost invariably make innumerable mistakes. But wasps, with a brain that is smaller than a pinhead, accomplish their specific tasks perfectly and without