National Geographic : 1951 May
The National Geographic Magazine by many Occidental observers in Thailand, Burma, Malaya, India, and other countries and islands of Southeast Asia. "I saw such a sight on the river near Bang kok," Dr. Henry R. O'Brien, of the United States Public Health Service, told me recently. "A shrub about 8 or 10 feet high was full of fireflies going on and off together. Except that the lights, of course, were not as bright, it reminded me of one of those Christmas trees with lights that turn on and off automati cally." Other reports tell of the same phenomenon on a much larger scale, thousands of fireflies in riverbank trees for a hundred yards or more flashing on and off in regular rhythm. What invisible cheerleader, if any, they fol low, is still the fireflies' secret. "Look for the woman," the French say. This has been advanced as a possible solu tion in the case of our common Photinus pyra lis, males of which sometimes flash in unison over a half-acre area. What happens may be this, according to a study by Dr. Buck: A male gets a response from a female, and several other males near by wink back simul taneously, taking their cue from her or from the one that found her first. Their lights together are bright enough to stimulate an other female several yards away. Males near her answer with one accord, and their flash ignites a third female who in turn gathers her coterie of males. This chain reaction goes on till many flying males are flashing on and off as one. Fire Beetles Worn for Adornment Ordinary firefly light, that of P. pyralis, was found by Dr. William W. Coblentz, of the National Bureau of Standards. to have a usual strength of one 400th candlepower. Less bright, but often sustained for minutes at a time, is that of the big "fire beetle," Pyro phorus, family Elateridae, of the American Tropics. Four or five together make a light strong enough so newspaper type can be read. People keep these fire beetles in little sugar cane cages and wear them by night as living jewels. In religious processions in Panama, for example, beetle brooches and hairpins gleam with eerie greenish light in the dark ness.* Often more than an inch long, the beetles have twin "headlights" that glow with green light; on their underside a yellow light shines intermittently in flight. Girls attach them unharmed to dress or hair by passing a pin under a natural hook of chitin at the joint of the beetle's body (page 703). Like our common firefly, the big fire beetle can be attracted by a flashlight mistaken for a female's glow. Collecting specimens this way in Jamaica, Dr. E. A. Chapin, Curator of the Division of Insects at the Smithsonian In stitution, felt like the target of tracer bullets. "I never got so I didn't flinch when the male came in, he flew so fast," Dr. Chapin told me. One Looks Like a Lighted Train With a red headlight and eleven pairs of green lights glowing along the sides, the wormlike wingless female of a large South American beetle, Phrixothrix, related to the firefly, looks so much like a lighted train that the creature is called the railroad worm. Similar, but lacking the red headlight, are North American species of the genus Phengodes. In Cuba Dr. Harvey of Princeton found what appeared to be a luminous frog. The mystery was solved when it proved that the frog had been dining on fireflies. Birds seem to be more fastidious. Smith sonian and U. S. Department of Agriculture studies indicate that fireflies rarely if ever are eaten by birds. Fireflies as well as small boys appear to react excitedly to Fourth of July firecrackers. Dr. Rudolf Ruedemann, of the New York State Museum at Albany, reported in Science that on the evening of the Fourth he "was startled by the sudden flashing up of the entire grass plot in front of him when some boys fired cannon crackers . . . about 80 feet away." In the grass or within a foot above it, scores of firefly lights flared on and flashed at a faster pace than usual until the cannon ading died. One possible explanation might be that the little creatures were shell-shocked. The in sect's sensitivity is shown by the common observation that the impact of near-by human footsteps will cause the larvae of Photuris and other species to glow. When injured, a firefly seems to go into a frenzy of flashing. One has been caught in the screen door and hurt. It blinks rapidly, throbbing with light, as if its luminosity is pouring out with life itself. Outside in the fragrant night the dance of light and life goes on, the insect constellations rising higher as dusk fades into dark. Myriad mating flashes foretell that a new generation will carry the torch when spring comes round again. * See "Panama, Bridge of the World." by Luis Marden, NATIONAL GEOGRAPHIC MAGAZINE, November, 1941.