But Mary was growing excited. "See, she has put the worm down and is prying up the top of the hole. She has got it off. She is—"
"Ss-h," say I, for wasps can hear. Or, wait; that's quite dogmatic. Wasps fly away when you talk too loud. That's better. That's not judging wasp doing by what we can do. That is just telling an observed fact.
Mary "ssh"-ed, but she pointed a plump little finger; a finger trembling with excitement. The wasp had gone down into the uncovered hole with the worm. Then she backed out, found the lid, covered up the hole and flew away into the pickle-weed again!
In twenty minutes she came back, with another limp measuring-worm, straight to the covered hole; worm dropped on the ground; lid taken off; worm dragged in; wasp backed out; lid carefully replaced; flight to the distant jungle of pickle-weed again!
O, this was exciting. Mary fairly exploded into exclamations and questions after the wasp was well away. What are the worms for? Are they dead? The second one seemed to wriggle feebly a little on the ground by the nest while the wasp was getting off the lid. Will she bring more? Will she fill the hole full of worms? Now I knew the answers to some of these questions, for I had been in this happy place before, but I wanted Mary to find out, to discover—exquisite and prideful pleasure—for herself. So I remained dumb.
Three more times the wasp brought worms. Three more times went through all the performance. But the last time she didn't come up for a long time; that is, for several minutes, and when she did come, instead of putting the salt crust on the hole, she got a little pellet of soil and dropped it in; and then another, and many others. Sometimes she scraped them in with her front feet, but there weren't many bits of soil close enough for that, for she had carried them all a foot or so away as she brought them out of the hole. She worked very industriously: jumping and running about, making little buzzing leaps and flights, until she had quite filled up the hole with the five dead worms in the bottom.
Then she did the most wonderful thing. With her fore feet she pawed and raked the surface until it was quite smooth, and with her jaws and horny head she pressed down and tamped the fine bits of soil until they were a little below the surface of the salt crust around the hole, and then she brought again the little circular lid or top of salt crust and carefully put it in the little depression on the top of the filled-in burrow, so that it fitted perfectly with the hard uncut salt crust around the hole's edge!
This is true. Does it seem wonderful to you? Why? Because we think that other animals cannot do what would be a very simple thing indeed for us? Our wasp was evidently concealing the whereabouts of her worm-stored burrow. I don't say that she wanted to conceal it; or decided to conceal it; or even intended to conceal it. She was simply, I say, concealing it. That seems quite certain, doesn't it? Well, this action of cutting out and replacing the bit of salt crust over the burrow was about the simplest and most effective way of concealing the hole that could be reasoned out, if we ourselves were to undertake it. The wasp, and all the other wasps of the same kind in our marshes, concealed their holes in the way that our reason would suggest to us as the best way. But I do not say anything about the wasp's mental processes toward getting at this behavior. One thing is pretty sure. Among a score or hundred of us doing this work, there would be pretty sure to be some to do it in a different sort of way from the others. The wasps of the same kind all do it alike. Perhaps that is the chief difference between reason and instinct.
But if our digger-wasp—whose name is Ammophila, the sand-lover—made Mary's and my eyes bulge out by her cleverness, what shall we think of that other Ammophila that Dr. Williston watched on the plains of Kansas, or that other one still which the Peckhams studied in Wisconsin? These other Ammophilas, instead of using their hard heads to tamp down the soil in the hole, hunted about until they found a suitable little stone which, held tightly in the jaws, was used as a tool to pack and smooth the dirt! And the Kansas wasp did another odd thing. Instead of making its hole of the same caliber or width all the way down, the upper half-inch or so was made of greater diameter than the rest of the burrow so that a little circular shelf ran around the inside of the hole half an inch below the top. Now when the clever Kansas wasp closed the burrow each time it went away to hunt for measuring-worms, it did it in a curious way. I quote the exact words of Professor Williston, the observer: "When the excavation had been carried to the required depth"—this is our professional way of saying, when the hole had been dug deep enough—"the wasp, after surveying the premises, flying away, soon returned with a large pebble in its mandibles, which it carefully deposited within the opening; then, standing over the entrance upon her four posterior feet, she rapidly and most amusingly scraped the dust, 'hand over hand' back beneath her till she had filled the hole above the stone to the top. [The stone of course was resting on the little circular shelf half an inch down in the hole.] ... When she had heaped up the dirt to her satisfaction, she again flew away and immediately returned with a smaller pebble, perhaps an eighth of an inch in diameter, and then standing more nearly erect, with the front feet folded beneath her, she pressed down the dust all over and about the opening, smoothing off the surface and accompanying the action with a peculiar rasping sound."
Is this not a creature of wits, this Kansas wasp? And an undaunted worker? For each time she went away to get a nice fat looper, she covered up her hole in this elaborate way, and each time she came back, she had to remove the half-inch of tamped-down soil and the little covering stone resting on the shelf in the hole.