The common lightning-bugs of Europe are _Lampyris noctiluca_ (Plate IX., Fig. _d_) and _L. splendidula_ (Fig. _a_). Their life history is an interesting study, and a brief description will apply to all. In early spring we find the little yellow eggs, perhaps gleaming with the wonderful phosphorescence, and thus finding protection, attached to blades of grass or other objects just above ground. The _larva_ (Plate IX., Fig. _c_), a long, narrow, flat creature, soon appears and begins a predatory life; even being provided with an apparatus for removing the mucus of its victim. About the month of April it attains its full vigor, and during the summer changes to the pupa form, or hibernates all winter, entering a deep sleep, and assuming its new shape the following spring. We see the light from the very first in the eggs of some; then in the _larva_, there appearing like little sacs on the under surface, one on each side of the middle line, so arranged that the insect can hide them by retracting the body, and causing them to blaze out when the abdomen is extended. Nothing in all nature is more wonderful than the changes through which these and other insects pass before attaining adult growth. The _larva_ is a busy little creature, full of life; but, when about to change, it becomes lethargic and quiet, as if impressed with the importance of the coming metamorphosis. Finally it wriggles out of its old skin, and becomes a _pupa_, also luminous; exceedingly lively, yet with its motions restricted. It moves its _antennæ_ and legs, and pushes itself along by movements of the abdomen. Finally the perfect insect appears, with its wondrous array of lights, so little understood, and which, if accompanied with the ordinary amount of heat attendant upon such a display, would soon roast or fry its possessor. As to the use of the lights, we can only conjecture. It has been shown that one insect recognized the other by it, and thus it may be a sign language; while, according to others, it is a warning to birds and other enemies.