We had been lying quietly on the white salt sand in one of the unroofed marsh rooms for some time this September day before we saw the first wasp begin to work. She was standing on her head, apparently, and biting most energetically with her jaws, cutting a little circle in the salt crust. When she got the circle all cut, she tugged and buzzed until she dug up, unbroken, the little circular piece (perhaps one-third of an inch across) of crust. She dragged this about three inches away. Then she returned to the spot thus cleaned and dug out with her sharp jaws a bit or pellet of soil. Holding this in her mouth, she flew away about a foot and dropped it. Then came back. Then dug out another pellet of soil and carried and dropped it a foot or so away. Then back again and so on until it was plain that she was digging out a little cylindrical vertical hole or burrow. As the hole got deeper, the wasp had to crawl down into it, first with head and fore legs, then with head and half her body; finally her whole body, long legs, wings and all, was hidden as she dug deeper and deeper. She had to come out of the hole of course to carry away each bit of dug up soil. She always backed upward out of the burrow, and all the while she was digging she kept up a low humming sound. It was this humming sound that attracted our attention to other narrow-waisted wasps like the first one. By moving about cautiously and listening and looking carefully, we found more than a dozen others digging holes, each one going about the work just like every other one. When our first wasp had made its hole deep enough--this took a pretty long time; we found out later that it was about three inches deep--she brought back the first little circular piece of salt crust and carefully put it over the top of the burrow, thus covering it up entirely and making it look as if no hole were there. Then she flew away, out of the little bare room and off into the pickle-weed somewhere. We waited several minutes but she didn't come back, so we turned our eyes to another wasp near by which had its hole only just begun. It was interesting to see how closely like the first wasp this second one worked. Prying and pulling with the jaws, the same fluttering of the wings and humming, the same backing out of the hole and the swift little flight for a foot or two feet away from the hole to drop the pellet of soil. I tried to point out to Mary that this was the way animals do which work by instinct and not by reason. That all the animals of the same kind do things in the same way, and that they do them without any teaching or imitating or reasoning out. They are born with the knowledge and skill and the impulse to do the things in the particular way they do. But Mary found this very tiresome and let her eyes rove, and it is well she did or we might not have made our great discovery: a really thrilling discovery it was for us, too.