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Firefly Nature Notes

Fireflies and glow-worms are beatles which belong to the family Lampyridae. In fact there are more then 2000 lampyrid species which occur thought the temperate and tropical zones, except in deserts and high mountains. Synchronised, rythmic flashing is only seen in the region stretching from India east and south-east to the Philippines and New Guinea.

It is the folded-wing fireflies (Pteroptyx sp.) which have developed this striking synchronous flash pattern. The species Pteroptyx tener occurs along tidal reaches of the Selangor river. They may be found singly or in groups ranging in size from a dozen or so, to tree-loads of thousands in estuarine mangrove swamps. Synchronous flashing may not always develop, especially if numbers are low.

Display trees are chosen from species with open foliage (Sonneratia caseolaris or locally known as "Berembang") by the Selangor river. Only certain of these trees are selected. Sonneratia sp. grows on tidal streams or coastal area within the influence of a river. The fruits are edible, but astringent. Commonly, associated with Acicennia alba ("Api-api hitam"). The same display trees may be used over a long period (recorded up to 5 years), and riverman in Malaysia are said to use firefly trees as navigation marks.

Fireflies develop from eggs and larvae living in the soil or in water. The larvae are carnivorous, probably feeding on nematodes (small round worms), copepods (small shell-less and shrimplike) and midge larvae. Adult live for about one month in captivity given sugar and water. Male and female are easily distinguished by their light organs.

Light organ of the female- and male firefly.

A few fireflies remain in the display tree by day, but at the Selangor river, most leave the tree at dawn and are found in grass blades and other foliage until one hour before dusk. Flashing begins one hour after sunset at the rate of 3 flashes per second. It takes 15-20 minutes for flashing to build up from onset to peak. Only the male flash in synchrony. The display is most briliant during a period of 2-3 hours after onset, but flashing continues at low levels until half hour after sunrise. Individuals synchronise by adjusting to previously observed flashing of neighbours, and newcomers quickly develop the synchrony of the tree. Trees which are close together may flash in time.

Males take up flashing stations on leaf edges or leaf points within trees and probably defend the surrounding leaf area. Because the males are spread out, they give the impression of artificial tree lights. They aim their lanterns (to attract females and repel male?) by bending the abdomen downwards; and with the tip nearly touching the leaf, their light is directed forward and laterally. Males may enter into a brief flash dialogue with flying and glowing females. or they may chase after females, both sexes twinkling in flight. Long distance unidirectional flights are made by females possibly seeking sites to lay eggs. On these flights, the fireflies flash about once every 3 seconds.

Why synchrony?

The flash rhythm is species specific and probably attracts females to males from long distances. Further explanation is still controversial. One authority suggests that synchrony within small groups is groups is important, as it attracts more females to the group and therefore to each of the component males. The problem with this explaination is that there is no evidence to suggest that fireflies in display trees make up small groups. The theory also fails to explain why distant groups within the same tree flash together.

Another authority points out that male fireflies probably compete for females by increasing the brightness of their flashes. They suggest that males must flash together in order to let females compare the different flash intensities. Just after a flash, females are less responsive, so a late flash is seen as a dim flash. The problem with this theory is that a clever male firefly which flashed just before everyone else would be seen as brighter by a passing female, and should therefore be chosen.

Scientist are clearly having headaches trying to explain why fireflies flash together. See what ideas you come with after viewing this mysterious and beautiful light show.

Directions to Fireflies Watching

From Kuala Lumpur to Petaling Jaya, go along the Kuala Selangor road for approx. 56 km or 35 miles till you reach Bukit Rotan which is at a T-junction. There is a Hindu temple on the left - take the right fork signposted to Kampung Kuantan approx. 3.5 miles away and follow the signposts to the fireflies watch jetty by the Selangor river.

Make advance reservation for a boat which will take a maximum of 4 passengers. Fees include boat fee (boatman cum guide and insurance), entrance fee (into the park?) and a fee for parking at the designated carpark. Be there at about 7.30pm ~ proper shoes (sneakers) with adequate protection against mosquitoes are advisable. There is a refectory where you can have your refreshment after the boat ride up and down the Selangor river.

The trip is not recommended for rainy nights as less fireflies are out or during full moon as they are not so bright or spectacular. The best time to watch is 1-4 hours after sunset.

This article (revised slightly) is distributed free as a pamphlet to visitors.
Author annonymous

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