It is in the genus _Pyrophorus_ that we find the most remarkable light-givers; the different species being found principally in tropical America. In Plate XI. _Pyrophorus noctilucus_, a form common in the West Indies and Brazil, is shown. It ranges from 1.50 to 1.75 inches in length; is a black or rusty-brown color; and, if observed during the daylight, two conspicuous oval spots of a yellowish white hue are seen on each side of the prothorax. These are the lanterns of the Elaters, and in the dark glow with a brilliancy far exceeding that of the lightning-bugs. These lights shine from above, while between the part known as the metathorax and the first abdominal segment gleams another, or lower light, even more brilliant than the other: so the _Pyrophorus_, turn which way it will in its flight, emits a flash of light. The light appears to be dependent upon the will, as when feeding or asleep it is not seen; attaining its greatest brilliancy during activity and flight. The color of the light, as seen by the author, is a rich green; but the eggs emit a light of a bluish tint, according to Dubois. This naturalist has made some extremely interesting experiments with this beetle. The eggs which he dried retained their luminosity for a week, the light re-appearing when they were placed in water. He ground the luminous organs in a mortar, after having dried them in vacuum, and then mixed them in boiled water; the latter immediately becoming luminous. Dr. Dubois concludes that the light of the _Pyrophorus_ is intended as an illuminator for itself alone. To prove this, he covered one of the upper lights with wax, and the animal moved in a curve; when both spots were covered, the beetle soon stopped, and then moved in an uncertain manner, carefully feeling the ground with its _antennæ_. The spectrum of the light was extremely beautiful, being continuous, without dark or brilliant rays; and, what appears most remarkable, the composition of the light was found to change with its intensity. As to the exact cause of the light, how it is produced, the secret yet rests with Nature. Dr. Kidder thus refers to the brilliancy of one of these wondrous light-givers: “Before retracing my steps, I stood for a few moments looking down into the Cimmerian blackness of the gulf before me; and, while thus gazing, a luminous mass seemed to start from the very centre. I watched it as it floated up, revealing in its slow flight the long leaves of the palm _Euterpe edulis_, and the minuter foliage of other trees. It came directly towards me, lighting up the gloom around with its three luminosities, which I could now distinctly see.”