Novelist Nathaniel Hawthorne once noted that "if moonlight could be heard, it would sound just like this".

'This' refers to the songs of crickets. Crickets, together with katydids and grasshoppers, belong to a group of insects known as the Orthoptera. These critters are characterised by their ability to produce sounds, many of which can be heard within humans' audible frequency range.

Concerto at dusk
During the day, the forest soundscape is dominated by cicadas and birds. But as night falls, a different group of animals turn up. They are mostly the crickets and katydids. Since most people would not wander into the forest at night, few would have experienced the twilight orchestra of the forest.

It was only recently published that there are as many as 150 species of Orthoptera in the small forest patch of the Bukit Timah (BTNR) and Central Catchment Nature Reserves (CCNR). The males of different species produce unique sounds to attract females of their respective species. This is achieved by rubbing the stridulatory apparatus on their forewings, consisting of the stridulatory files and resonating surface such as the mirror (a cell that acts as a resonator) - contrary to popular belief, crickets do not make sounds by rubbing their legs together.

Some crickets produce high-pitched thrills, others low-pitched hums; some sounds are majestically deafening and can be heard metres away, while others are soft and gentle. Indeed, the combination of different melodies and harmonies would create an orchestral score that  Beethoven or Mozart would be proud of.

One of these crickets is not like the others
Interestingly, many crickets may look very similar in appearance and yet produce very distinct sounds. For example, there are two species of crickets recently discovered only in Singapore that look nearly identical: Jerelyn's forest cricket (Phaloria jerelynae) and the Timah forest cricket (Tremellia timah).

The calling song of Jerelyn's forest cricket consists of a series of double chirps whereas that of Timah forest cricket consists of a series of thrills. The differences in their songs gave me some hint that they are dissimilar. After dissection and examination of their internal reproductive organs, it became clear that they actually belong to different genus of crickets!

Taking them under our wing
Such information has important implications for conservation. The range of the Jerelyn's forest cricket is highly restricted to only a small part of BTNR, whereas the Timah forest cricket is more widely distributed across the reserve. Jerelyn's forest cricket could easily have gone extinct without being documented, simply because it could have been misidentified as the Timah forest cricket.

Along with Jerelyn's forest cricket and Bukit Timah forest cricket, 14 species of crickets and katydids new to science have been discovered from Singapore over the past two years. Many of these are found only in Singapore and nowhere else in the world. Many more species are still waiting to be documented, serving a timely reminder that the fauna of BTNR and CCNR, and Singapore, remains rich and diverse, with many new and mysterious species still waiting to be unveiled.

By Tan Ming Kai

The female adult of the Timah forest cricket (Tremellia timah). The females of both species of forest crickets look almost identical at first glance.

Scambophyllum pendleburyi is one of the many beautiful orthopterans which may be found in the forests of the Bukit Timah and Central Catchment Nature Reserves.

Cardiodactylus singapura is a very common cricket found in Singapore but was only described in 2011!

The female adult of the Jerelyn’s forest cricket (Phaloria jerelynae). The elongated rod-like feature is the ovipositor with which the female lays its eggs.

This female katydid (Nahlaksia bidadari) is named after the former Bidadari Cemetery which has been slated for development. Although not found in the cemetery, this new species was named after Bidadari to serve as a reminder to future generations of Singapore’s heritage.