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Thu 17 Jun 2004

Cicada showers at Labrador Park

Category : nature

Labrador has been well known for its cicadas for many, many years and sometimes they make their presence felt beyond the perpetual chorus of their high-pitch calls.

On 8th June 2004, when I left Labrador rocky shore for Car Park B, I noticed a light wet spray floating down from the cliff's canopy. The adult cicadas had emerged again at Labrador Park! Though certainly not in the scale of Brood X in the US!

The tree on which the numerous adult cicadas (the young are underground) were perched is a Purple Milletia (Millettia atropurpurea), a legume - thanks for confirming the identity, Angie. This tree has been a host to cicadas for many years. I remember DH Murphy being lifted up by a tree-pruner to get a closer look a decade ago in the mid-90's. Parks & Recreation (now NParks) had asked him for help after receiving curious calls from the public. It was quite the event and even made the evening news!

Cicadas belong to the group of insects called homopterans. These are true bugs with piercing and sucking mouthparts and feed on plant juices.

Strangely enough, cicadas feed off the water-carrying xylem vessels of a tree. In order to extract enough nutrients, the insects have to extract several hundred times their body weight in fluid, resulting in the cicada shower! Furthermore, xylem vessels are under negative pressure and extracting fluid thus requires even more effort. Nutrient carrying plant sap flowing through the phloem, on the other hand, oozes out of a plant when tapped upon. Aphids for example, are sap suckers. It is believed this is why sap suckers are smaller than xylem-feeders.

While cicadas in Singapore are not as seasonal as their temperate cousins, I often wonder if this adult emergence and feeding is seasonal. Certainly they seem to be excreting liquid during the warmer part of the year - it is always an odd scene seeing a puddle beneath a tree in very hot weather! Well, at least the cicadas are keeping cool!

Left - Angie Ng and Ng Hua Qin watching the cicada shower from the Purple Milletia at Labrador Park. Right - spray from the cicadas against the cliff forest creating a misty appearance on a hot clear day. Inset: the red arrow points to a cicada perched on a tree branch.

Left - Cicada specimen from Department of Biological Sciences, facing Kent Ridge, from May 2004. Adrian Loo noticed the dead insect and brought it over to my table. The red arrows point out the length of the proboscis, the piercing and sucking mouthpart of the insect. It spans almost half the body length. Right - close up of Cicada excretion, which is pumped out periodically from the abdomen as a fine spray.

Posted at 4:54PM SGT by N. Sivasothi | permalink | , .