Macauley, U. S. Army, relates that, in a mosquito-infested region of Montana, he was told how the mosquitoes had disappeared, as if by magic, on the sudden appearance of a brood of devil's-darning-needles or dragon-flies of rather large size. The agency of this insect in the matter was corroborated by the evidence of squaw-men and Indian traders, who said that the flies did not appear every mosquito year, but, when they did, they came in droves and cleared the mosquitoes out. They were called "mosquito-hawks." The captain himself afterward had an opportunity of observing them at work, and to determine that they were dragonflies. "I noticed," he says, "that they flew in an irregular kind of skirmish-line, moved slowly, and every now and then made what he described as short 'dabs' at apparently nothing. Mr. Heistand said that 'each one of these dabs means a mosquito.' I was curious to see how deliberate they were about it, and how fairly aligned the skirmish-line was. They appeared somewhere about 11 a. m., and when I went into the post later I crossed the parade-ground and saw detachments of about half a dozen flying slowly about. They stayed at about an average of three feet from the ground. I do not know how late they kept it up or how early they began. They stayed until all the mosquitoes appeared to be gone." Dr. Lamborn also tells how his own attention was drawn to the subject. It was while he was in the forests of Lake Superior, railroad-building. "Sitting in camp while supper was being prepared, I often, with a sentiment of gratitude, looked through my mosquito-veil at the dragon-flies that collected in the open spaces among the pine-trees. They darted from side to side like swallows in a meadow, but with amazing rapidity, and at every turn, the natives assured me, 'a mosquito ceased from troubling.' Afterward I happened to observe an entomologist feeding a dragon-fly that had eaten thirty house-flies in rapid succession without lessening his voracity. What thought could be more natural than the one that came to me, that an artificial multiplication of dragon-flies might accomplish a mitigation of the mosquito pest?"
Mr. Beutenmuller, of the Museum of Natural History, New York, avers that "the dragon-flies (Odonata), especially the Æschinus, Gomphina, and Libellulina, are the natural enemies of the mosquitoes; they are voracious—they sometimes appear in great numbers, and, as a matter of fact, the mosquito disappears before them, while their breeding-grounds are, in many respects, similar, so far as fresh and brackish water habitats are concerned; and, finally, in the metamorphosis of the dragon-fly we meet conditions which introduce it in antagonism to the mosquito at the same stages of development." The dragon-fly, however, prefers sunlit areas, and will not live in the woods.