It was a fatal day for the crickets. Between nine o’clock and one, sixteen had been packed away, enough to provision three cells, as we knew from former observations. Her manner was brisk and energetic, as she ran about poking her head into every likely hole. At one time we saw her dislodge a cricket which tried to escape by hiding under some brush. She pursued, there was a lively scrimmage, and it was pulled out quite limp and was then held in the mandibles, back up, while she gave it a prolonged sting under the neck, after which it was carried home without further manipulation. At another time she paused in her homecoming to give the victim one long squeeze at the neck. The crickets were placed in pockets, neatly arranged on their backs with their heads inward and their long legs projecting into the main tunnel. They were alive when taken, but died from day to day in the laboratory, the larvæ eating them in this state without criticism. While we were watching we noticed a much smaller wasp hovering about, and presently she slipped into the nest. When the owner returned and found her, there was a slight commotion in the passage–way, and then the inquiline appeared, shaking her wings in a flippant manner, as though she cared nothing for an encounter with the Big Blue. Instead of coming out immediately as usual, cœruleum stayed inside for twenty–five minutes. We should like to think that she was occupied in finding and destroying the egg of the parasite, but we have no reason to suppose that she could recognize that menace to her fortunes. Cœruleum lives in her nest and enlarges it from day to day to fit her necessities. On going over to the island one morning we found a cricket sleeping calmly in the entrance way, little guessing how dangerous was its position. It did not budge until the wasp came creeping up from below, when it jumped away to a place of safety. Before the day’s hunting began, a long study of the locality was made on foot, tufts of grass, weeds and stones being carefully noted, and this accounts for the ease with which the nest is afterward found.