When we found that quinquenotatus was a very common species, and that nearly every day brought us a fresh example, we thought that we had the question of its stinging habits in our own hands. What could be easier than to carry a strix about with us and to exchange it, when opportunity offered, for the paralyzed spider of the wasp? The good results obtained by Fabre and Marchal from this manœuvre made us confident of success. We did not doubt that when the wasp came for her spider and found it livelier than it ought to be, she would repeat the stinging operation before our eyes. Accordingly, the next time that we saw quinquenotatus digging we made a diligent search for her spider, and soon found it on a bean plant five feet away. Just as we discovered it, however, the wasp swooped down and carried it to some purslain, close to the hole, where she hung it up again, while she went to make her final preparations at the nest. We seized our chance, and quickly substituted a fresh strix for the one that had been paralyzed. According to the habit of its species when danger threatens, it kept perfectly quiet, and when the wasp returned it was hanging there as motionless as a piece of dead matter. How she knew the difference was a mystery, but she would not touch it. She seemed to think that she had made a mistake in the locality and that her own spider must be hanging somewhere close by, for she hunted all over that plant and then over several others near to it, returning continually to look again in the right spot. After five minutes she gave it up, circled about three or four times, and flew off in the direction of the woods to catch another spider. Why did she go to the woods? When she realized that the strix she had stung was gone and that she must have another, why did she not take the one that hung there in plain view? Our failure could not have been due to the fact that we had handled the spider, since, when on other occasions we took one that had been paralyzed, examined it and then returned it to the wasp, she accepted it without hesitation. Disappointed though we were at the irrational conduct of our wasp, we resolved to await her return and to try again. In forty minutes she came back with another spider, but instead of taking it into the nest she hung it upon a bean plant near by and then proceeded to dig a new hole a few inches distant from the first. Foolish little wasp, what a waste of labor! Truly, if you are endowed with energy beyond your fellows you are but meagrely furnished with reason.