Summer World_ A Season of Bounty - Bernd Heinrich [28]
The hornet nest contained three horizontal combs that were hung one below the other, and this nursery was enclosed with multiple layers of insulating paper. The cells of the combs gave clues to the minimum wasp population the nest had produced. The oldest (topmost) comb had the smallest cells, which would have been the “cribs” of worker larvae (and their pupae). There were 240 of these, showing the silk tops of the cocoons where the young wasps had chewed their way out. The second two tiers of combs had larger cells; the first of these tiers had 212 cells that probably each produced a drone, and the lowest comb with the largest cells contained 257 large (queen) cells. The twenty-eight comatose queens still in the nest would have come from them, as well as the 220 additional queen cells. This comb had grown from a central point outward to the periphery, since the empty cells from which sixty-eight adults had emerged were in the center, surrounded by a ring of fifty-four now dead pupae (still in capped cocoons), in turn surrounded by 135 cells, also with dead larvae. The largest larvae were located toward the inside of the ring. There had been many casualties in this wasp colony—a loss of 46 percent of the total production of reproductives attempted; the summer had been too short for many wasps. However, since at least 212 drones and 40 new queens had successfully left the nest, it was probably not too short for the life of the colony.
A colony that faces a short summer, as in the arctic, has little option but to start making the drones and queens soon after the colony is founded and without building up a large worker force. However, in New England a colony could invest more time and energy in workers, the infrastructure of what Edward O. Wilson has called the “fortress factory,” if there is assurance that it can reap the benefits of making good on the investment later on. Rearing many workers before switching over to the desired “product” is gambling that the weather will hold out. But a hornet (wasp) queen cannot be overambitious and push her luck too far in the summer, so that she ends up with a nest full of hundreds of larval young that will then all die when the cold sets in and the summer food runs out.
Of five other nests that I examined, four had switched over to make drones and queens in time to get all of them out of the nest to adulthood, but although they had many fewer casualties than the high producer, they also had less output of “product.” On the other hand, the colony that waited the longest to build up its strength before switching to make its product lost 20 percent of its offspring, but it had the largest overall output—about 900 drones and queens—and this is what ultimately matters to wasps. Thus, its more modest “gambling” for a long summer season had paid off despite the loss of some offspring.
My interest in hornet nests is probably matched only by that of a bird, the red-eyed vireo. This bird uses the paper from hornet (wasp) nests to decorate its own nests. I have examined many dozens of vireo nests over the years and have seldom failed to find at least a patch or two of hornet paper conspicuously attached to the outside surface of each nest. Given what hornets can do, I felt that this bird has a strange taste for nest decoration, because the wasp paper was not serving as insulation on the birds’ nests. Furthermore, the apparently obsessive behavior of putting one or more patches of flimsy wasp nest onto the outside of the birds’ nest involves costs. Hornet paper is hard to come by. One can search for a hornet nest for many days and not find one, even in winter when such a nest is conspicuous from as much as 100 feet away.