Mangroves Full of Fireflies Blinking in Unison
MATHEMATICIANS are embroiled in a new round of debate as they try to explain one of the leading mysteries in nature: why do trees full of Southeast Asian fireflies flash in unison?
The unusual insects, beetles of the family Lampyridae, have long fascinated scientists. Experts hope greater understanding of the insects' strange ways will help explain a number of analogous phenomena, including the synchronous firing of cells in the human heart's natural "pacemaker," the brain cells that emit electric signals in rhythm and the cells in the pancreas that control the release of insulin. A recent study of such pancreas cells has shown that they produce coordinated signals only when working in a group of 50 or more.
A number of mathematicians are now arguing that synchrony comes naturally to a variety of oscillating systems. These include not only fireflies but a number of other organisms and body cells that have a preferred rate of natural oscillation. Blinking Causes Debate.
The fireflies live on mangroves and other trees found on riverbanks throughout Southeast Asia. The insects gained scientific prominence in 1935, when Hugh M. Smith, a biologist in Washington, described them in the journal Science. His report was greeted with widespread disbelief; some scientists called the blinking an illusion, others called it a fleeting coincidence. But his description has since been confirmed by the careful observations of many scientists.
Imagine,a tree 35 to 40 feet high thickly covered with small ovate leaves, apparently with a firefly on every leaf, and all the fireflies flashing in perfect unison at the rate of about three times in two seconds. Between flashes the tree was in complete darkness,
Imagine,a tenth of a mile of river front with an unbroken line of Sonnerati trees with fireflies on every leaf flashing in synchronism, the trees at the ends of the line acting in perfect union with those between.
In the early part of this century, it was proposed that the males of the species evolved to blink in unison so that the light would penetrate the dense vegetation along tropical rivers and attract females. Other specialists have been sceptical. The existence of a "maestro" who sets the pace like a band leader seems to be ruled out because each fly can see only about 100 others.