Summer World_ A Season of Bounty - Bernd Heinrich [33]
Using a sharp knife, I cut into the first nest and was surprised by how hard the walls were. This first nest I examined was divided vertically into only two cells. There were no spider remains in either one; the prey had already been eaten by the wasp larvae, down to the last leg. I cut into an adjacent nest, and here the lowest compartment contained eight fully intact spiders; these were of different sizes but were all similar and probably belonged to the same species. As I pulled them out, one by one, they wiggled only slightly. Each raised its front legs briefly in a defensive gesture, then quickly let them droop. However, as long as I didn’t touch them they remained motionless. The largest of the eight spiders had a yellow oblong egg attached to its side. The compartment above this one (sealed off from the one below) also contained eight live spiders of the same type. Only one was dead—it had a collapsed, flaccid abdomen with fluid leaking out, a sign that the wasp larva was eating it. One compartment, the upper one, contained a pill-like pupa; the lower compartment had a dead larva that was as flaccid as the spider being eaten, so I assumed it was diseased and dead.
The following summer, however, I learned that the flaccid, seemingly dead larva probably hadn’t been “diseased” at all. I had saved several nests to rear out the wasps. Three wasps emerged, and to my great surprise they were not organ-pipe mud daubers. Instead, they were scoliid wasps. Scoliids are well-known parasites of scarab beetle larvae, such as those of June beetles that live in the ground; apparently here was a species of wasp that parasitizes a mud-nest-dwelling larva of another wasp.
Although only the females build and provision the nest, the male organ-pipe mud dauber is one of a very few that stay around during the nesting. He is thought to help guard the nest against potential intruders while the female is away hunting prey for feeding the young (when the nest is left open). Apparently males had been absent at the parasitized nests I had found, or else they had been negligent. In this case the male’s apparent negligence resulted in the death of his and the female’s offspring. However, in other instances, when flies enter the nest to lay eggs that feed on the wasp’s prey, the larva’s food, the offspring are not necessary killed. Instead, they grow into miniatures because of food deprivation (O’Neil et al. 2007).
My observations of nature from our front porch soon led to other, even more startling surprises. You may have guessed it—a few days later, as we were again sitting on the front porch drinking our usual after-supper glass of red wine in the gathering dusk, I thought I saw a light-colored piece of straw about half a foot long “flying” horizontally and then hovering in midair. That caught my attention—I looked closer and saw a black wasp that seemed identical in form to a mud dauber, and it was carrying an object. I jumped up in my excitement, and the wasp was spooked and flew off. The proof eluded me, but it dropped its “prey” onto the porch. I picked it up—definitely a long piece of dry grass!
Expecting the wasp to return, I waited. After about twenty minutes it did return, carrying another piece of grass. This time I was ready with an insect catcher net, and I snagged the wasp along with the grass it carried. The wasp was about 0.6 inch long, and the blade it was carrying was about 2.4 inches long. The wasp looked superficially almost identical to the mud dauber, but its body was black rather than black-blue and its wings were smoky-colored instead of blue-black