junction of the head and thorax; the older larva has also numerous luminous points along the sides of the body near the spiracles. It is remarkable that there should be three successive seats of luminescence in the life of the same individual. The eggs too are said to be luminous. The light given off by these Insects is extremely pleasing, and is used by the natives on nocturnal excursions, and by the women for ornament. The structure of the light-organs is essentially similar to that of the Lampyridae. The light is said to be the most economical known; all the energy that is used being converted into light, without any waste by the formation of heat or chemical rays. The subject has been investigated by Dubois,[134] who comes, however, to conclusions as to the physiology of the luminous processes different from those that have been reached by Wielowiejski and others in their investigations on Glow-worms. He considers that the light is produced by the reactions of two special substances, luciferase and luciferine. Luciferase is of the nature of an enzyme, and exists only in the luminous organs, in the form, it is supposed, of extremely minute granules. Luciferine exists in the blood; and the light is actually evoked by the entry of blood into the luminous organ. We have given to this family the extension assigned to it by {260}Schiödte. Leconte and Horn also adopt this view, except that they treat Throscides as a distinct family. By most authors Eucnemides, Throscides, and Cebrionides are all considered distinct families, but at present it is almost impossible to separate them on satisfactory lines. The following table from Leconte and Horn exhibits the characters of the divisions so far as the imago is concerned:— Posterior coxae laminate; trochanters small. Labrum concealed; antennae somewhat distant from the eyes, their insertion narrowing the front Eucnemides. Labrum visible, free; antennae arising near the eyes under the frontal margin Elaterides. Labrum transverse, connate with the front. Ventral segments six; claws simple; tibial spurs well developed. Cebrionides. Ventral segments five; claws serrate; tibial spurs moderate. Perothopides. Posterior coxae not laminate; trochanters of middle and posterior legs very long Cerophytides. [Illustration: Fig. 135—Larva of _Fornax_ n. sp. Hawaii. A, Upper side; B, under side: _s_ _s_, position of spiracles; C, head more enlarged; D, under side of terminal segment; _a_, anus.]