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Thu 31 Mar 2005

Hundred(s) of cicada moults on Pulau Ubin

Category : nature

Most of us have heard the drone-like calls of cicadas in our forests but rarely seen them. They have an interesting life cycle which takes them from tree root to tree-top.

Eggs are laid in small grooves cut into tree bark or shoots. When the eggs hatch, the larvae drop to the ground and burrow into the soil. Feeding on the sap of tree roots, the larvae or nymphs grow each time they shed their exoskeleton (moult). Unlike butterflies, they do not undergo complete metamorphosis so there is no pupal stage, and the nymphs look very much like the adults.

Upon maturity, the cicada nymphs emerge from the soil as a group and climb up trees. They shed their exoskeleton for the final time (terminal moult) and emerge as winged-adult cicadas, leaving behind moult skins we may see on tree trunks in forest, which are light-weight, translucent, and which retain the morphological details right down to the fine hairs!

Up in the tree canopy, the cicadas feed and the resulting spray can be quite noticeable - see this report from Labrador Park from June 2004.

Meanwhile, the din we hear are of the males calling for a mate - hence we hear cicadas rather than see them. We do see moults once in awhile and very rarely see the actual insect.

Chim Chee Kong was fortunate recently in encountering a "cicada exoskeleton graveyard" left behind after the terminal moults of an emerging cicada nymph brood! He wrote -

"Hi Siva,

I was cycling in Pulau Ubin on Good Friday (25 Mar 2005) when I saw a hundred or more (could be in the hundreds!) moulted exoskeletons of cicadas left behind on tree trunks (e.g. Angsana) and underside of leaves (e.g. Rubber).

I could not see the cicadas themselves (except for one that was left behind), but they were making deafening music all around me!

The exact location is a shaded area on gravel path after the "3 bridges" (a Pedal Ubin term referring to the area between Sungei Besar and the prawn ponds) leading to Jalan Noordin.

Cheers,
Chee Kong"

Chee Kong included four photos of moults on trees and several closeups. They have been posted to Habitatnews' Flickr account.

Read about the 17-year periodical cicada, in particular, Brood X which emerged last year in the US - link.

Posted at 1:34PM SGT by N. Sivasothi | permalink | , .