The French Pelopæi differ from ours at nearly every point. Ours kill only about two thirds of their victims, many of the others being paralyzed so perfectly that they live for two or three weeks. Again, ours, instead of placing the egg upon the first spider, almost invariably lay it upon the last one brought in. Another point of difference is that our larvæ frequently start in by eating up the soft abdomens, like children who first devour the plums in their pudding, returning later to the tough parts that are left, a rash and reprehensible course of action of which their better-taught French cousins are never guilty. When one comes to compare the two sets of facts furnished by the two groups of species, the deductions which Fabre has drawn as to the importance of the instincts of the French group are seen to be unfounded. The American species violate nearly every principle which he considers necessary to their existence, and yet they flourish and multiply. For our part we find nothing in the actions of Pelopæus that needs to be explained—nothing that is not well adapted to the conditions under which each species works. The measure of praise or blame which we mete out to these depredators is merely a way of saying whether we would or would not follow their methods in provisioning our houses and rearing our children. Perhaps we would always use large spiders and would always have them fresh; but it is evident that tastes differ, and the matter is so purely a subjective affair that it will have to go unsettled. In any event, whether her victims be strong or feeble, old or young, big or little, fresh or dry, they certainly serve admirably in enabling Pelopæus to rear brood after brood, and to people the different parts of the earth with abundant representatives of her kind.
Chapter XII
SENSE OF DIRECTION
WE once made a number of experiments to discover in what way the social wasps came back to the nest on returning from their hunting expeditions. Were they endowed with some innate power which made memory of places unnecessary, and enabled them to fly in a straight line to any point they wished to reach, or did their return depend upon the more commonplace method of remembering the appearance of the country-side?
One morning at half past eight, we placed a wasp cage over the opening of a yellow-jacket hole that had been closed since the night before, and caught fifty-five workers, after which the nest was again closed, one of us taking the cage out on to the lake, while the other remained to watch for their return.
At seven minutes before nine, twenty of the wasps were liberated an eighth of a mile from shore near the end of the island. All, without exception, flew toward the island and away from the nest. Whether they settled could not be determined. The boat was then moved an eighth of a mile beyond the island to the north, where, at ten minutes after nine, the remaining wasps were set free. They seemed a good deal confused, and flew in all directions. Many returned to the boat and alighted, but soon flew away again. Two that settled on the boat were knocked into the water; but they instantly rose and circled up into the air until out of sight.
Of the fifty-five wasps that we set free, thirty-nine returned to the nest by ten o’clock, five of them belonging to the lot that flew to the island, since they soon found their bearings and came directly home, reaching the nest before the wasps of the second lot were liberated.
Of the thirty-five wasps that were set free at the second point, at least twenty started in wrong directions. Adding these to the first twenty, we have left only fifteen that appeared to know where to look for their home, and yet thirty-nine reached the nest in a little more than an hour from the time the first wasps were set free.