Holder, in his work on phosphorescent animals, either quotes or refers to Prescott as saying that “when the Spaniards visited the country”—that is, Mexico, “the air was filled with the _cucujo_, a species of large beetle which emits an intense phosphoric light from its body strong enough to enable one to read by. These wandering flies, seen in the darkness of the night, were converted by the excited imagination of the besieged into an army of matchlocks.” Surely, from such a foundation, something as superior to it as are our cultivated fruits, or domestic breeds, to the wild stocks from which they sprung, might in no long time be produced, since it is not to be supposed but that some individuals of the _Pyrophorus_ give a stronger light than others. The above passage, by the way, if it be from the _Conquest of Mexico_, as one might suppose it to be, is most carefully concealed in the index, which, however, it might very well be, and yet exist, as I know from much teasing experience. As to the matchlocks, would to Heaven the old Mexicans, as well as the Peruvians, had had them, or, still better, 11-inch Howitzers. I might then have something more to say about these wonderful beetles. All I can add now is that the light appears to be used by the insect as a guide to its own movements, since when the celebrated Dr. Dubois covered one of the side ones with wax, this caused the individual so treated to walk in a curve, and when “both spots were covered it soon stopped, and then moved in an uncertain manner, carefully feeling the ground with its antennæ.”[151] But I do not know if “both” here means all three of the lamps, or only the two upper ones. If there be any luminous insect that eclipses the _Pyrophorus_ it must be the great lantern-fly—also of South America—provided only that the great lantern-fly _is_ luminous. That is a most essential point, and it does not appear yet to have been satisfactorily made out. The principal evidence on the affirmative side is that of Madame Merian, who was right about the _Mygale_—the great bird-killing spider—and who here speaks as an actual eye-witness. Her account is as follows: “The Indians,” she says, “once brought me, before I knew that they shone at night, a large number of these lantern-flies, which I shut up in a large wooden box. In the night they made such a noise that I awoke in a fright, and ordered a light to be brought, not knowing from whence the noise proceeded. As soon as we found that it came from the box we opened it, but were still more alarmed, and let it fall to the ground in a fright at seeing a flame of fire come out of it; and as many animals as came out, so many flames of fire appeared. When we found this to be the case we recovered from our fright, and again collected the insects, highly admiring their splendid appearance.”[151]