Firefly MangroveENRO

Every firefly keeps its own time.

Together

0%each on their own

BlindWatching closely
How it works ↓

A night river

Firefly Mangrove

On some rivers in Southeast Asia, thousands of fireflies settle in one tree at dusk and begin to flash in step. None of them leads.

Here they start out of time. Watch them find each other.

What is real here#

Along some tidal rivers in Southeast Asia, fireflies of the genus Pteroptyx gather in mangrove trees at night and flash together, so that a whole tree seems to switch on and off. In 1690 the German physician Engelbert Kaempfer travelled down the Chao Phraya and described a tree whose fireflies lit and went dark in unison; his account was published in 1727. Hugh M. Smith published a note on the synchronous flashing of fireflies in Science in 1935. John and Elisabeth Buck studied it in Thailand in October 1965 and published their findings in 1966; their 1968 paper documented the synchrony in Pteroptyx malaccae with photometer readings and film.

Fireflies can be pulled into the rhythm of a flashing light. In separate experiments, a New Guinea firefly and Pteroptyx malaccae adjusted the timing of their flashes in response to artificial flashes. In this simulation, the fireflies near the lantern you hold try to match it.

What the model does#

Each of the 380 fireflies has its own clock, a little faster or slower than the others: about one flash every 1.7 seconds, give or take about 7%. Each follows one rule: adjust your timing to the flashes of the fireflies near you. Most of the pull comes from neighbours in the same tree; a smaller share comes from the whole river at once. The slider sets how strongly they respond. It climbs by itself over about a minute, and you can take it over at any time.

“Together” is a single number for how aligned the clocks are. Picture each firefly as an arrow on a circle, pointing to where it is in its cycle. The number is the length of the average arrow: 0% when the arrows point every way, 100% when they all point the same way.

The rule is a version of the Kuramoto model of coupled oscillators that mixes local and river-wide coupling. It is a simplified picture, not a recording and not a model of any one species. Buck and Buck reported a flash period of 560 milliseconds for Pteroptyx malaccae at 28 °C, about 1.8 flashes a second and three times faster than here. Models built for the insects, such as Ermentrout’s of Pteroptyx malaccae, let each firefly adjust its own rhythm as well as its timing. Here the flashes are slower so the eye can follow, and the sound is invented: a soft bell for each flash, and a low hum that grows with the order.

Sources#

  • Kaempfer, E. (1727). The History of Japan, translated by J. G. Scheuchzer. London. Vol. I, Book I, ch. III, pp. 42–45 (Siam, 1690; fireflies on p. 45). en.wikisource.org
  • Smith, H. M. (1935). Synchronous flashing of fireflies. Science 82(2120): 151–152. doi.org
  • Buck, J. & Buck, E. (1966). Biology of synchronous flashing of fireflies. Nature 211: 562–564. www.nature.com
  • Buck, J. & Buck, E. (1968). Mechanism of rhythmic synchronous flashing of fireflies. Science 159(3821): 1319–1327. doi.org
  • Hanson, F. E., Case, J. F., Buck, E. & Buck, J. (1971). Synchrony and flash entrainment in a New Guinea firefly. Science 174(4005): 161–164. pubmed.ncbi.nlm.nih.gov
  • Moiseff, A. & Copeland, J. (1997). The effect of flash duration and flash shape on entrainment in Pteroptyx malaccae, a synchronic Southeast Asian firefly. Journal of Insect Physiology 43(10): 965–971. doi.org
  • Ermentrout, B. (1991). An adaptive model for synchrony in the firefly Pteroptyx malaccae. Journal of Mathematical Biology 29: 571–585. doi.org
  • Kuramoto, Y. (1975). Self-entrainment of a population of coupled non-linear oscillators. Lecture Notes in Physics 39: 420–422. doi.org