_Photuris versicolor_ is noticeable by its frequent resting on a twig or leaf in the woods, when it will gradually increase the intensity of its light till it glows like a torch; then it gradually fades to a spark, and becomes quite extinct. It thus remains unseen for some time; but in about a minute, or it may be two, it will begin to appear, and gradually increase to its former blaze; then fade again,--strongly reminding the beholder of the revolving light at sea. The light of this species is of a brilliant green hue. Gosse says he has seen a passing _Pyg. xanthophotis_, attracted by the glow of a stationary _Phot. versicolor_, fly upward and play around it; when the intermingling of the green and orange rays had a charming effect. The smaller species have, some a yellow, and some a green, light. _Pyg. xanthophotis_, when held in the fingers, will frequently illuminate a segment of the abdomen, over which the light plays fitfully, sometimes momentarily clouded, more or less, but generally saturated, as it were, with most brilliant effulgence. This species occasionally comes in at open windows at night, but much more rarely than the _Photuris versicolor_ and the smaller kinds, a dozen or more of which may be seen almost every night, crawling up the walls, or flitting around the room and beneath the ceiling, of these Jamaica homes. One of our commonest forms in the eastern United States is _Photuris pennsylvanicus_. It is about one-half of an inch in length, has a general yellowish color, with a few stripes or lines of brown or black. Both sexes have wings and quite long _elytra_. [Illustration: PLATE X. 1. _Scopelus humboldtii_, showing luminous spots. 2. Mother o’pearl organ from side of same. 3. _Argyropelecus._ 4. Longitudinal section of organs from abdominal region of same. 5. Luminous organ from nasal region of _Ichthyococcus_. 6. Luminous Crustacean. 7. Lampyris. 8. Light cells of same, and trachea (magnified).] In the diurnal _Lucidota_, often seen flying in shady places, and to be remembered by the peculiar, disagreeable, milky fluid they exude when caught, the luminous organs are feebly developed. In the female they are indicated by yellow spots found on the last ventral segment, and on the last two in the male. In the genus _Pyropyga_ the light organs are inconspicuous, except in one species,--_luteicollis_. In _Pyractomena_, an attractive genus, this peculiar feature is well developed in both sexes, and the light vivid at times. The phosphorescent organs are larger in the male, and situated on the fifth and sixth ventral segments. Close examination will show in the male a large, stigma-like pore on each side, midway between the middle and the side, whose office is not perfectly understood. In the female the lanterns are at the sides of the segments. _P. lucifera_, found from Massachusetts to Texas, has extremely small luminous organs.