Research Reveals Secret of the Firefly's Glow, and Experts Now Seek Better Illumination Through It about the twen- ty-sixth day of incubation. They require about (wenty-twe months to reach maturity, at which time they pupate (emerge as adults.) "In mature larvae, about a half day before pupation, the cells of the fat spheres, which lie near the hypodermis (under skin) in the lower part of the sixth and seventh segments, are liberated Left, Abdomen of Adult Development or Malc; Right, Abdomen of Firefly's Light Adult Female, Showing Organs in Abdomen Further Development of of Larva. Light Organs. tist has never lost the curiosity which all human beings have when they are children. You lost interest in fireflies and "cold light" when you grew up. The scien- This "Automobile Bug" or Pyrophorus Noctilucus, tist, on the other nand, kept right on Common in the Southwest, Has Its Light Organs in a re ut oa the Upper Part of Its Body, Instead of in Its Tail. hii ne expert They Shine Through Two "Headlights" menting with the On Its "Shoulders." ever saw a firefly? It was probably when you were a toddling child. And. most likely it was a quiet Summer night, just after. a shower. You saw it flitting across the lawn or higher among the dark tree branches-- flashing its little tail-light off and on in a way that was fairy-like, mysterious and altogether entrancing. Presently, perhaps, you saw a thousand of them, and you thought it was the most wonderful sight you had ever seen. And then--if you were a normal child with a child's destructive curiosity--you started chasing fireflies. If you lived in these United States you probably called them "lightning bugs." And if your parents didn't stop you, you put them in a bottle and hid the botila under your pillow in the nursery, and after the other lights had been put out yon brought the bottle from its hiding place and found you had a substitute for a mar --with the advantage that lightning bu couldn't burn your fingers or set fire to the sheets. In short--you "discovered" and made use of the principle of "cold light." But it was a feeble light at best--not much good for practical purposes. And as you grew older you lost your interest in fireflies--unless you happened to become a scientist. ~~ The chief difference--perhaps the only fundamental difference--between a sclen- tist and an ordinary man is that your scien- C'- you remember the first time you light they gave. He put them in his lab- oratory instead of under the nursery pil- low, but he was actuated by the child's idea. He thought they might be made to yield a light that wouldn't burn his fingers or "set fire to tife sheets." Such a light, obviously, would be of great value for scientific and commercial pur- poses if it could be perfected. Every method of lighting now known produces a great quantity of heat. The sole object of a candle, lamp or electric bulb, when used for illumination purposes, is to produca light. Yet 92 per cent of the energy goes off in heat and only" 8 per cent is trans- formed into light. The process that goes on in a firefly's tail, apparently, produces 99 per cent light and only a fraction of 1 per cent heat, if any heat at all. If science, patterning after the firefly, invents a method by which all the combustion energy is used in light, without heat waste, arti- ficial light would be infinitely less expen- sive than it now is. "We'll try to find out what causes the light in the firefly," argued the scientists, "and then maybe we can produce the same kind of light on a larger scale." And science at last has solved the mystery, though it hasn't yet been able to adapt its discoveries to practical commercial uses. The latest and most interesting discoveries in this field have been made by Professor Walter N. Hess, of Cornell University. Professor Hess decided to experiment with the common firefly that he saw on Summer nights on the university campus* at Ithaca, New York. It is called the Photorus Penn- sylvanica. Instead of Large Drawing Shows Another View of the "Auto- mobile Bug." The Arrangement of the Internal Organs Is Not Correct in Anatomical Detail, but Is Simplified to Indicate the Manner in Which Scientists Believe the Light Organs Operate: a Layers of "Cold Fat" or Luceferin. b Windpipe. ¢ Breathing apparatus. d Tubes Through Which Oxygen Is Conveyed to Luminary Organs. ¢ Transparent Tissue Through Which Light Is Projected. Above, Cross Section of Adult Male's Organs of Light; Right, Cross Section of Larval Light Organs Showing Reflectors. and become distributed along the lower skin. They cgntain numer ous fat globules, which appear dark after treatment with osmic acid. "The fat cells which are liberated from the fat spheres during the last day of larval life and the first onc or two days followl pupation, compose a layer about three cells deep above the hypodermis. Some of these cells are shown in the light organs. "The undifferentiated cells of the light organs, at this stage, are all of the same --- \, > Trap-Mouthéd Fish, Thaumatichthys Pagydostomus, Dredged Up From Depth of 3,000 Feet. Light Organs in Roof of Mouth Attract Small Sea Creatures, and Mouth Closes With a Snap on Its Prey. beginning with the firefly itself he began with its eggs. An insect goes through three stages before it becomes mature. First it is an egg. Then it becomes a larva or worm. Then if enters the pupa stage (the stage during which it under goes final transformation). And, last of all, it becomes the full-fledged insect. When Professor Hess had collected two complete sets of eggs, larvae and pupae, he was ready to begin the study of the development of the light-producing organs in the firefly. He discoveréd that the substance with which fireflies produced light was neither phosphorescent nor electrical. He discov- ered that it was "cold fat." Here is his own language: "The first indication of the formation of light organs in the embryo is noticeable at the age of fifteen days, just as the em- bryo revolves from its backward turned position and starts to coil up. "At this time groups of fat cells, with their large globules, which are colored dark by osmic acid, migrate ventrally in the segments and come to lie in the region of the future light organs. The undiffer- entiated light organ cells are now contin- uous with the groups of fat cells above them. "As soon as the fat cells become local {ged in the region of the future light organs. their dark-colored globules of fat becomo smaller in size and fewer in number. In fact, in the fifteen-@ay embryos there ap- pears to be a gradual gradation from the cells lying next the skin, contain- ing smaller and fewer globules, to the fat cells near the central part of the body, which contain more and larger globules. "In the sixteen-and seventeen-day embryos the light organs are regu- lar in outline and they have be- come separated from the other fat cells. The fat globules are now smaller and fewer in number than on the fifteenth day. All cells that compose the light organs are ap- parently new of the same histo logical (animal tissue) structure. "At the age of twenty days there begins to take place a differentia tion of the cells of the organs into the photogenic (paraffin) and re flector areas. "At the age of twenty-two days the light organs of the embryos be- me functional and appear as twd- ute histological or animal tissue appearsncd, which suggests a common origin. "The cells In the photogenic (or paraffin) and reflector layers, in the five-day pupae, are clearly differentiated. At this time the cells of both layers still contain some dark colored fat globules. The rapid division of the cells affects the trachea or air tubes of the body of the insect, so that later these alr tub8s invest the light organs. "Shortly before the light organs become mature in both embryo and pupa the fat globules disappear and the organ takes on its characteristic adult structure. The light organs of both larva and adult are formed from fat cells which become dif ferentiated into photogenic and reflector layers of the mature light organs. Hence the light organs are entirely mesodermal (or of middle of the body origin)." It will be seen that Professor Hess finds that the light organs of animals originate within the animal itself, and that cold light is manufactured from fat, the same as heat-bearing light. ¢ The lightning bug 1s by no means the only living creature that emits cold light. There are other Insects on land, including the amazing Pyrophorus Noctilucus of "automobile bug," familiar in the Southe west, which has two "headlights" on the front part of its body. In the sea there are hundreds of light-producing creatures, one of which is reproduced on this Some of them have "headlights" stuck oa antennae that project like long eyes from the front of their foreheads; others have luminous organs inside the roofs of mouths; others hive luminous tails, ous spots, and some glow all over at cer tain periods. Experiments at Princeton by Dr. Ulrle Dahlgren, who has published more finpore tant monographs on luminous creatures than any other scientist, have been con ducted with materials obtained from & crustacean in Japanese waters. He obtained notable results, but the m as yet are too expensive for commercial use. The Germans are also at work on the same problem. v Dr. Dahlgren affirms that the light produced by a substance he terms ferin. It is the same thing Dr. Hess "cold fat." Dr. Dahlgren believes becomes luminous by a process tion. To what extent the animals trol the light and by what exact the oxidization takes place--if it zatipn--is still undetermined, strides are being made, and you prepared to hear at any time scientist has perfected a method "cold light" ful to the world, : E i Eg ge % Re sbicathibieit